21 CFR-11 – The guideline 21 CRF, part 11, issued by the American FDA authority, regulates the technical and organisational requirements which must be fulfilled in order to use electronic data and documents instead of paper in the development, authorisation and production processes.


ACC range – ACC-range (Active cooling control area according to DIN 12876 standard) is the operating temperature range during operation with an active cooling unit. Example: working temperature range: -30 to 150 °C, ACC area: -30 to 100 °C. This information implies that the cooling unit cannot work continuously at temperatures of above 100 °C. The working temperature range is equal to the ACC-range in all LAUDA devices.

Actuator – The actuator is an active component of the so-called control circuit. It is controlled through an adjusting command (see control variable) of the controller (see temperature controller) and triggers a measure that counteracts to the control deviation.

Adsorption – The accumulation of (amphiphilic) molecules at the surfaces and interfaces of liquids and solids. This leads, amongst other things, to a reduction in surface/interfacial tension.

Air-Blast cooling systems – Self-contained units, supplied with a liquid to air heat exchanger, circulating pump, fan and control gear. They are designed to remove heat from a process in which the coolant temperature can be above the ambient temperature (this is typically 10°C above the ambient i.e. 25°C ambient equals 35°C onto process).

Ambient temperature range – The permissible temperature range of the environment in which the unit functions perfectly. It is 5 to 35 °C for all LAUDA units given in this catalogue with the exception of the Integra and WK units. For the latter the upper limit is raised to 40 °C. This is especially important with respect to applications in industry.

ATEX – Directive 94/9/EC, also known asATEX 100a, has been issued by the EC in order to harmonise fundamental safety and health requirements for devices, protection systems and components that are provided for use in accordance with the regulations for hazardous areas. This definition includes devices for safety, test and control that are required for use outside hazardous areas with regards to their explosion risks. Directive 94/9/EC is applicable to electric and non-electric devices, protection systems and components (electric and non-electric operating supplies).

Automatic cooling – A procedure used in cooling thermostats to save energy. The controller decides by means of suitable control logic whether the cooling unit can be switched off, as is the case in a warming-up process. As a result of the automated cooling an automatic sequence corresponding to the temperature control program has been made possible with cooling thermostats with built-in or external programmers.


Bath depth – The overall dimension from the upper edge to the bottom of the bath. Since the liquid may generally be filled to a maximum of 20 mm below the upper edge, the usable depth is stated as a value that is 20 mm less than the bath depth.

Bath opening – The usable surface that is available for direct thermostating, as a rule over the entire usable depth. Exceptions are the Ecoline thermostats with baths 003, 011, 019, 025 and 006 T, in which the usable area is reduced due to the conical shape of the bath as it narrows towards the bottom.

Bath thermostat – A thermostat which is equipped with a bath that also holds the object to be thermostated. The built-in circulating pump is preferably used to mix the bath liquid, but can also be used if necessary to convey the liquid through an externally connected circuit, e.g. connection of a through-flow cooler to allow the cooling of heating thermostats.

Bath volume (also filling volume) – The volume of the bath liquid that is required for appropriate operation of the thermostat, but without considering the volume of the bath liquid in the external liquid circuits. If two values are given, the lower value indicates the minimum required amount, the upper value the permissible maximum amount. The difference is the so-called expansion volume. Especially in the case of circulating applications, a large expansion volume is advantageous, since the circulation thermostat must also take up the expansion of the liquid in the external circuit. This expansion volume is especially large with process thermostats.

Bath/circulating thermostats – Thermostats with an adequate bath opening to hold objects for direct thermostating in the bath or a circulating pump for closed or open external circuits.

Billmeyer formula (IV value according to Billmeyer) – Serves the purpose of the approximate calculation of the intrinsic viscosity of polyesters and others. No additional polymer characteristic data required.

Boiling point – The boiling point identifies the temperature at which a liquid begins to boil. This temperature is dependent on atmospheric pressure, and the boiling point is therefore specified at a standard pressure of 1013 mbar.

Bubble pressure tensiometer – Used to determine the surface tension of liquids from the pressure in gas or air bubbles that are generated in the measuring liquid with a capillary of known dimensions. This method is not suitable for determining interfacial tensions between liquid phases.

Bus system – See interface.



Calibration thermostat – A bath thermostat with especially high temperature stability and especially consistent spatial temperature distribution. The test samples used in the bath are compared with a temperature reference standard (calibration) and adjusted to the desired value as necessary.

Cascade control – See external control. Circulation chiller (also circulating chiller) – A special cooling thermostat which is designed exclusively as a circulation thermostat. Circulation chillers are designed as independent units in terms of their type of construction, the cooling and pump capacities. They are often used as a substitute for mains water-cooling.

Circulation thermostat – A thermostat in which the bath liquid is conveyed through an open or closed external circuit. Circulation thermostats can have a thermally decoupled active surface, as in the case of the USH 400 and the process thermostats, whose surface temperature does not match the operating temperature. They do not have a freely accessible bath.

Clear-view thermostat – A bath thermostat with a transparent back and front for direct observation of the tempering object preferably viscometers. Bath thermostats with transparent plastic baths are described as thermostats with a transparent bath and not as clear-view thermostats in the narrower sense. CMC measuring – The determination of the surfactant concentration at which the surfactant molecules begin aggregating into micelles (CMC concentration). This can be determined from the dependency between the concentration of the surfactant in the solution and the surface tension.

Component tested safety facilities – As a rule all temperature control units fall within the pressure equipment directive (see DGRL 97/23 EC). Depending on the heat transfer medium and the temperature, the installations have to be equipped with special safety facilities, for example safety valves, pressure, temperature or leveling switches. These facilities serve as a protection for the temperature control unit at exceeding the admissible limits of the application. In this connection it has to be strictly observed that only component-tested parts, i.e. qualified components, from a named testing laboratory are used. These components have to be equipped with the identification numbers of the named testing laboratory and conformity declarations of the manufacturers have to be on hand.

Compressor control – See injection control.

Condenser – See refrigerant.

Contact angle/contact angle measuring – characterizes the wetting properties of liquids on solid bodies. The contact angle can be determined by measuring individual drops on a solid or from the forces required to move a solid in contact with a liquid lamella. The contact angle is used to calculate surface energy.

Control circuit – Control circuit is the totality of control section (see control section) and controller. Sensors and signals, their processing and transmission also form part of the control circuit. For example, transformers, clamps and electric lines. Control deviation –

Control deviation is the deviation of the actual value from the preset setpoint.

Control section –Control section is the part of the control circuit to be influenced according to its application. Pipework, sensors and heat transfer areas with their walls and coatings also form part of the control section. Through distances from the test point to the final control element and through inertia at the heat transfer for example, a characteristic response time of a control section arises. Depending on the response time, a control section is classified from ‘good’ to ‘difficult’.

Control variable – Adjusting command of the controller that acts on the so-called actuator.

Controller characteristic – Different controllers are distinguished according to their so-called controller characteristic: proportional response (P-controller), integral response (I-controller) and differential response (D-controller). As for temperature controllers, combined characteristics have stood the test. Modern PID-controllers can be perfectly adapted to difficult control sections through freely eligible parameters. They are therefore widely used.

Controlling temperature – To control temperature means to control supply or carry away heating or cooling energy in order to reach a constant temperature at the consumer.

Cooling capacity – The effective capacity available in cooling thermostats or circulation chillers. The friction heat produced by the circulating pump and the heat penetrating as a result of insulation that is not ideal has already been taken into consideration.

Cooling capacity adjustment, automatic – Provided with the more powerful Ecoline cooling thermostats, this is a procedure to save energy. The controller determines by a suitable logic in the microprocessor whether it is possible according to the operating temperature and the cooling demand to set the required cooling capacity to a lower level. In addition to saving energy, this also saves wear and tear of the compressor, reduces the amount of heat given out to the environment, and gives better temperature stability.

Cooling cascades – If temperatures below -50 °C are to be produced with compression cooling units, so-called two-stage cooling units connected in cascades are required to bridge the difference between the cold side (evaporation pressure) and warm side (condensation pressure, e.g., ambient temperature). The high-pressure stage bridges the temperature difference from approximately ambient temperature down to -40 °C, for example. The low-temperature stage condenses at -35°C and evaporates at -90°C, for example. This requires special refrigerants with the corresponding thermodynamic characteristics.

Cooling power – With medium cooled heat exchangers the cooling capacity always depends on the temperature difference between cooling medium and heat transfer fluid. The cooling capacity reduces at falling outflow temperature and tends to zero when it reaches the cooling medium temperature. At mechanical cooling the characteristics are similar. The cooling capacity thus always relates to a definite outflow temperature. At LAUDA the performance data of refrigeration machines is based on cooling water or air with a temperature of 20°C.

Cooling thermostat – A thermostat whose working temperature range is also below the ambient temperature and preferably draws heat from the thermostating liquid.

Correction as per Harking and Jordan – Harkin and Jordan produced tables for correcting surface and interfacial tensions measured with a ring. These values are standardized.

Cracking – Breakdown of a liquid is produced by contact with oxygen at high temperatures or through high film temperatures on the heater. Cracking can be reduced by keeping the bath opening to a minimum. In addition the heaters of LAUDA thermostats are of optimal design so that unnecessary high film temperatures are avoided.

Critical micellar concentration (CMC) – At this concentration, surfactant solutions suddenly change their physical properties. The reason for this is the formation of organized aggregates (micelles) of the surfactant molecules when the critical micellar concentration is exceeded. The structure of the micelles is dependent on the character of the solvent and the structure of the surfactant molecules.



Delivery head – The delivery head is a theoretical value which is used within the pump characteristics (see pump characteristic) instead of the feed pressure (see feed pressure). The advantage is that the delivery head is valid for any given liquid. The feed pressure is then calculated for the respective feed medium by multiplying the density with the delivery head (see feed pressure).

Density – Density is understood to be the mass of a body per unit volume. In addition to depending on the material, this value is essentially affected by temperature.

Diffusion coefficient – characterizes the thermal migration movements of molecules in the material examined. In tensiometry, the diffusion coefficient refers to the migration of molecules in the liquid measured.

Discharge pressure – The over-pressure of the circulating pump of a thermostat directly at the pressure nozzle, measured with water. If only one value is given in the table, this is the maximum delivery pressure at flow rate zero. In the diagrams the delivery pressure is given in relation to the flow rate.

Discharge suction – is the suction of the circulating pump (pressure/suction or Duplex pump) directly at the suction nozzle, measured with water. If only one value is given in the table, this is the maximum suction at flow rate zero. In the diagrams the discharge suction is given in connection with the flow rate.

Drop Volume Tensiometers – Determine the surface/interfacial tension of liquids at the moment of drop separation, from the volume of the drop that is formed in air or in an immiscible second liquid. The densities of the phases concerned must be known in order to calculate the surface/interfacial tension from the measured drop volume.

Du Noüy ring – A measuring body made of a platinum-iridium alloy to determine surface/interfacial tension from the tensile force of a lamella produced by this body using a ring/plate tensiometer.

Du Noüy ring method – Used to measure the surface/interfacial tension using a standardized ring with a ring/plate tensiometer. The ring is immersed into the liquid and then drawn out. This forms a liquid lamella that is stretched to its maximum. The surface/interfacial tension is calculated from the resulting force. The calculated value must be corrected.

Duplex pump – The LAUDA Duplex pump is a pressure/suction pump with built-in constant level controller in the thermostat. It is suitable for connection to open and closed circuits in the same way as the pressure/suction pump. The Duplex pump is offered as an option exclusively for the Ultras. Dynamic interface or surface tension – The measurable reduction in interfacial/surface tension with time due to adsorption of surface active substances. Dynamic measuring process (tensiometry) – Used to calculate the surface/interfacial tension dependent on the surface age.

Dynamic viscosity – Is essential to the shear flows, viscosity coefficient, between shearing strength τ and speed gradient D in τ = η D, and has the unit mPas (formerly centipoise, cps).



EasyUse Operation – In the LAUDA Proline, this comprises: drain taps – for cooling thermostats even at the front, rollers and handles for increased mobility, double pump connection for the parallel connection of two external systems, and switching of the circulation (bypass). Further features include the detachable console (Command version) for use as a remote control and the quick-change of the required interface. This facilitates comfortable work.

Emulsion – A disperse system consisting of two immiscible liquids, such as water or an aqueous solution and an organic. The dispersed or inner phase is present in form of small droplets, surrounded by the dontinuous or matrix phase.

Environmental temperature range – This is the admissible temperature range in which the unit can be operated in accordance with the regulations.

Evaporator – See refrigerant.

Expansion volume / Expansion tank – When heating up the heat transfer medium to the desired operating temperature, the heat transfer medium expands. This expansion volume results from the expansion coefficient, the temperature change and the contents of the unit. The expansion tank installed in the temperature control unit has to collect the expansion volume safely. The assessment of the dimensions of the expansion tank for thermal oils depends on DIN 4754. The following applies for hot water: about 0.8 % per T = 10 K., for mineral oils: about 1 % per T = 10 K. and for silicone oils: about 2 % per T = 10 K.

External control – If the outflow temperature is not the controlled and a temperature measured outside the temperature control unit is used, then the outflow temperature of the heat transfer fluid is tracked in such a way that the setpoint is reached at the external point. In practice this is achieved via a so-called cascade control (see cascade control). The so-called ‘master controller’ produces in its capacity as the control variable (see control variable) the setpoint for the post-connected slave controller (see slave controller), the slave controller controls the outflow temperature of the heat transfer medium liquid.

External control – A temperature control by which the thermostat is controlled from a connected external system. Temperature probe is therefore required in the external system that is connected to the thermostat. The set value entered at the thermostat is compared with the actual value in the external consumer and applies temperature control to the thermostat in the sense of a cascade controller. Depending on the operating temperature, insulation losses and exothermia, the bath temperature and thus the inlet temperature of the consumer can be considerably above or below the set value.



FDA – Abbreviation for the Food and Drug Administration, United States. Prescribes binding guidelines for the development and production of pharmaceutical products: is internationally valid.

Feed pressure – Feed pressure is the manometric pressure measured at the outlet nozzle of a pump or a compressor. As far as pumps are concerned, the feed pressure also results from the pump characteristics and is the product of delivery head (see pump characteristic) and the density of the flow medium.

Fill volume – In connection with a LAUDA unit, the recommended filling amount of the system (volume) which is required in order to guarantee a trouble-free operation, and to allow for expansion or contraction of the system throughout its operating temperature range.

Film temperature – The maximum film temperature, which the manufacturer indicates with reference to organic heat transfer mediums, describes the temperature at which the heat transfer mediums begin to decompose. Especially when organic heat transfer mediums are heated up with the help of electric heaters, attention must be paid to the heat flux values because otherwise the heat transfer medium is destroyed by a high surface or film temperature. In this connection it has to be proven through a flow or a heat technological layout according to DIN 4754 that the admissible film temperature cannot be reached with an adequate safety distance.

Fire point – The fire point according to the EN 61010 standard is the most important criterion for the upper limit of a bath liquid. According to ISO 2592 it is the temperature at which a liquid in an open vessel burns for at least 5 seconds. The fire point of a bath liquid is decisive for its maximum permitted temperature that must be not higher than 25 °C below the fire point.

Flash point – The flash point of a flammable liquid indicates the lowest temperature at which the vapour produced can ignite for a short time, i.e. for less than 5 seconds. The temperature limits of LAUDA bath liquids are mostly considerably below the corresponding flash point in order to avoid any danger.

Flow rate – The volume of liquid delivered per time unit by the circulating pump measured with water. If only one value is given in the table, this is the maximum flow rate at counterpressure zero. In the diagrams the flow rate is given depending on the discharge pressure (counterpressure).

Flow rate – Volume flow of a pump or a compressor. The flow rate depends on the respective operating point and the characteristics (see pump characteristic) of each component.



Glass viscometer – Viscometers made from glass, bearing different various designs, standardised in ISO 3105. The most common for automatic measurements is the Ubbelohde version with ventilation pipe.

GLP – Abbreviation for “Good Laboratory Practice”. Specifications initiated by the FDA American authority for laboratories and producers (e.g. of pharmaceuticals) regarding how tests and measurements are to be cleanly planned, performed and monitored. The guidelines have a legal character in many countries.

GMP/FDA – In processes in which the reaction temperature or the respective temperature control represent a critical quantity, the temperature control unit has to be qualified and validated. Qualification takes place according to the ‘Good Manufacturing Practice’ (GMP). If, for example, pharmaceutical products are produced for the American market, the manufacturing process – and with it the process equipment including the temperature control unit – is subject to the requirements of the American ‘Food and Drug Administration’ (FDA).



Hagen Poiseuill’s Law (fundamental equation of the capillary viscometry) – This forms the basis for viscometry in capillary viscometers. If the differential pressure is generated by a height difference in front of and behind the capillaries, hence: Vkin = k x t, (k: capillary constant, t: measured run of a defined volume of liquid). In the case of very short times, the non-dissipated kinetic energy must be taken into consideration (kinetic energy / Hagenbach correction).

Hazard evaluation (HAZOP) – As far as hazard evaluation is concerned, which has to be generated by the operating company, the information relevant for safety from the operating manual of the manufacturer has to be considered. These are especially: mounting and integration of the temperature control unit into the total system, commissioning, operation, maintenance and inspection and indications for possible improper use, as far as such an application has not already been prevented by the lay-out/technical measures.

Heat capacity – The maximum electrical capacity of the installed heater. In all LAUDA thermostats the heating is controlled in a quasi-proportional way. Startup and reaching the operating temperature is done at maximum power that is reduced automatically as the set value gets closer.

Heat transfer medium/Fluids – These are liquids that supply or carry away energy at the consumer. The heat transfer medium is supplied through a circulating pump of the temperature control unit. The bigger the circulating quantity, the lower the temperature difference at the consumer. The lower the temperature difference the better the control precision.

Heating power – With electric heating, the heating power is identical to the power consumption of the built-in electric heaters. It is always the maximum possible heating power and, in the case of electric heating, it remains invariable at all operating temperatures. With medium heated heat exchangers, the heating power always depends on the temperature difference between heating medium and heat transfer fluid. The heating power reduces at increasing outflow temperatures, and tends to zero when it reaches the heating medium temperature. The brought-in pump output is helpful but not taken into account.

Heating thermostat – A thermostat whose working temperature range is primarily above the ambient temperature and preferably adds heat to the bath liquid.

Heating/cooling thermostat – A thermostat whose working temperature range is above and below the ambient temperature, and which can either add heat to or extract heat from the bath liquid.

Huggins formula (IV value according to Huggins) – Serves the purpose of the approximate calculation of the intrinsic viscosity of polystyrenes and others, for example. KH is an additional constant dependent on polymer.


Ignition temperature – The ignition temperature is the lowest temperature at which a flammable substance in an air-liquid mixture ignites spontaneously and continues to burn without any addition of heat.

Immersion cooler – An additional chiller which is connected by means of a flexible and refrigerant-tight tube to a cooling coil for immersion and cooling of any desired bath.

Immersion thermostat – A thermostat that can be combined with a bath and so forms a separate unit. Immersion thermostats are equipped with a screw clamp to attach them to any desired bath wall or can be fixed on a stand.

Inherent viscosity (logarithmic viscosity coefficient) – The natural logarithm of the relative viscosity based on concentration C of the dissolved substance.

Injection control – With LAUDA process cooling units, the cooling power (see cooling power) is permanently controlled by adjusting the injection flow (0 – 100 %). The final control element is a continuously working control valve that is placed in the feeding pipe of the refrigerant in front of the evaporator. If several compressors are shunted, an automatic cascade connection (compressor controlled) ensures energy-saving partial-load operation.

Insulation type IP – As per EN 60529. The first figure states protection against contact and foreign bodies, the second figure protection against water. E.g., IP 32: 3 means protection against contact with dangerous parts located inside by using a tool of greater/equals 2.5 mm in diameter and up to 100 mm length. 2 means protection against drip water at angles of 15°. The assessment is done as per EN 61010-1 (see “Standards”). In the LAUDA range a statement of the IP type of insulation is only done for the Integral process thermostats and the WK circulation chillers.

Interface – Always serves to exchange data and may be set up on an analogue basis (mostly standard signal 4-20 mA or 0-10 V) or on a digital basis. In the digital area you find the single serial interfaces (RS 232) or the more powerful, parallel addressable systems for many users (RS 485 or the different industrial bus systems).

Interface, analogue – Used to input the set value or to output the actual value of temperature in analogue form, generally in the form of a reference signal with voltage (0 … 10 V) or current (0/4 … 20 mA) respectively. Interface, digital – Used to transfer data between connected units in digital form via data cable. The set and actual temperature values are the main items transferred. The RS 232 interface is of serial type and allows a point-to-point connection. This means that at anyone time only two participants such as the thermostat and the PC can communicate with each other via the interface. The RS 485 interface is an addressable interface to which up to 32 participants can be connected. Each participant of the bus system has its own address.

Interfacial energy – The sum of free energy of all the molecules present in the interface between different materials. The interface between a liquid and a gas is designated as the surface and the corresponding energy from this region is the surface energy.

Interfacial tension – The work that must be applied to increase the interface of the liquid by one surface area unit. This is equivalent to the specific interfacial energy.

Intrinsic temperature – The operating temperature of a heating thermostat that is reached when the heating is switched off in a stationary condition. It depends on the pump capacity, the bath liquid used and the installation of the thermostat, i.e. with or without a bath cover. The working temperature range only starts approximately 3 °C above the intrinsic temperature.

Intrinsic viscosity (limiting viscosity number, Staudinger index, IV value) – The limiting value of the reduced/inherent viscosity for the case of infinitely severely diluted solvents at disappearing shearing strengths:intrinsicviscosityIt is determined by measuring the vred as a function of the concentration and extrapolation on C = 0. For many polymers, there are approximation conditions based on the measurement of only one concentration usually specified in standards.



K value (according to Fickentscher) – A traditionally used relative mass for the mole masse for PVC and PVA.

Kinematic viscometry – Describes the quotients of the dynamic viscosity by the density: Vkin = η / ρ and has the unit mm²/s (formerly: centistokes, cst).



Lenard frame – Simple test wire. Is used as an alternative to the Du Noüy ring.

LIMS – Abbreviation for Laboratory Management System. Describes a system for the control and management of laboratory data, determined by various measuring devices.

Liquid to Liquid Heat Exchanger Modules – Self-contained units, supplied with a liquid to liquid heat exchanger, circulating pump, modulating liquid valve to control and conserve primary liquid and control gear. They are designed to remove heat from a process via factory or mains water that may be contaminated and therefore unsuitable for directly cooling the process.

Liquid-Air Fan Coil Units – Include a liquid to air heat exchanger and cooling fans. Heat exchangers are available in various materials to suit a range of applications and liquids.



Mark-Houwink formula – Provides the relation between medium mole masse (weight means) of the dissolved polymer chains and the intrinsic viscosity. For the absolute mole mass, the proportional constant K and the exponent a can be entered. These depend on the polymer and the solvent, and can be taken from the literature.

Martin formula (IV value according to Martin) – Serves the purpose of the approximate calculation of the intrinsic viscosity of celluloses and others, e. g. K is an additional constant dependent on polymer.martinformula Modular engineering – Describes the modular design from which any possible temperature control unit can be planned and assembled according to a recurrent pattern, thus saving on costs during the planning process, execution, commissioning, documentation and maintenance, because every module alone has already been approved many times. By using modular engineering, a maximum safety standard is achieved.

Monofluid (single fluid) system – This is a heat transfer medium that works with only one heat transfer fluid. It is useful when heating, cooling and freezing must be done simultaneously and heating and cooling units are working together.



Noise level – Measured according to the guidelines given in the DIN EN ISO 11200 standard for application of the basic standards, which are given there.



Oil Cooling Units – Self-contained units, supplied with an oil to air heat exchanger, circulating pump, fan and control gear. They are designed to remove heat from a process in which the coolant temperature can be above the ambient temperature (this is typically 10°C above the ambient i.e. 25°C ambient equals 35°C onto process).

Operating temperature range – The temperature range that is limited by the permissible lowest and highest operating temperatures. As a rule, this is only given for heating thermostats whose working temperature range can be extended to lower temperatures by means of auxiliary equipment, and the maximum to which it can be extended is the lower limit of the operating temperature range.

Operating temperature range – The temperature range that can be run in the heat transfer medium flow line to the process equipment (outflow).

Overlay pressure/Inert gas covering – Through an inert gas covering (nitrogen) on the expansion tank, oxidation of the heat transfer medium and seeping of water vapour from the air can be prevented. If the heat transfer medium is operated below its evaporation point, overlay pressure should be as low as possible (about 0.1 bar), so that when heating up through the reduction of the gamma space the pressure increase is not too high. If the heat transfer medium operated above its evaporation point and atmospheric pressure (1.013 bar), an overlay pressure of at least the respective vapour pressure is necessary in order to safely prevent cavitations. In both cases a safety valve has to be installed on the expansion tank.



Peripheral wheel pump – Peripheral wheel pump is a centrifugal pump with a running wheel that has a so-called ‘peripheral’ shape. The almost linear characteristics of a peripheral wheel differs fundamentally from the characteristics of a radial running wheel. At highest feed pressure and lowest feed flow rate the highest drive energy is required with the peripheral shape. Peripheral wheel pumps are especially suited for small feed flow rates and high pressures.

Permanent control deviation – Permanent control deviation is a purely proportional controller used; ‘permanent deviation’ is always the consequence. In this case the control variable(s) will always be proportional to the deviation. There is no adjusting command without deviation.

Plug & Play modules – Temperature control units and modules arrive at the construction site with clearly defined interfaces, ready for connection, complete with pipe work and insulated. They only have to be docked (see modular engineering).

Pour point – The pour point is the temperature at which a liquid becomes so viscous that it just ceases to flow.

PowerAdapt System – In the LAUDA Proline, the maximum possible heater power is used as much as is permitted by the network. This provides exceptionally high maximum heating capacities up to 3.5 kW even with cooling thermostats. Advantages: faster heating and optimum performance without overheating. The patented LAUDA heater control means that the loading effects on the laboratory voltage network are minimised. Moreover, the maximum power consumption – naturally at reduced heater power- is diminished to 10 A as required.

Pressure Equipment Directive (DGRL 97/23 EC) – Temperature control units are in the control of the pressure equipment directive considered as modules, which are assembled from several pressure devices (expansion tank, pipelines, fittings, safety valve, etc). The fundamental safety requirements for this are described in annex I of the pressure equipment directive (DGRL). The process of conformity assessment for the module to be applied depends on the category in which the module is classified. This category is determined through the highest category of the respective built-in pressure device. In this connection, parts of equipment with a safety function are ignored. The category that describes the hazard potential depends on the maximum operating pressure, heat transfer medium, content and type of the built-in pressure device. Before the temperature control unit is commissioned, the manufacturer has – according to the operating conditions – to classify the module into a category and to submit it to a process of conformity assessment. The temperature control unit has to be labelled with the CE-label and, starting from category II, has to be labelled with the identification number of the named testing laboratory.

Pressure pump – Used for the circulation of the thermostated liquid in an external closed circuit and in the bath itself (see also Vario pump).

Pressure/suction pump – This pump has a pressure and a suction level that are driven by the same motor. The bath liquid is conveyed from the pressure stage from the thermostat into the circuit, the suction stage draws the liquid back into the thermostat. A pressure/suction pump can be used in just the same way as a pressure pump for a closed circuit. It has the advantage compared to a pure pressure pump that the pressure in the external circuit falls from positive values (pressure) to negative values (suction) and is almost zero in the consumer itself. Thus it is possible to also thermostat pressure-sensitive glass vessels. In addition it is also possible to connect an open external circuit (a bath) with the aid of a pressure/suction pump. This cannot be done with a pure pressure pump, since this conveys the liquid only into the bath. Conveying the liquid from the bath back to the thermostat requires the additional suction stage. In any case a so-called level controller is required to maintain a constant level in the bath and this ensures that the flows of both pump stages are controlled so that they are equal. This is the only way that the level in the external bath can be maintained constant.

Primary side – Denominates primary energy carriers such as vapour, cooling water, air, brine, liquid nitrogen, etc. that have to be connected to the temperature control unit by the customer. These primary energies can be gaseous, vaporous or fluid.

Process thermostats – Process thermostats of the LAUDA Integra series are circulation thermostats in the heating and cooling range with high cooling, heating and pump capacities which allow quick cooling-down and heating-up speeds due to the small liquid volumes. They are ideal for temperature control in process technology.

Proportional cooling – Used in LAUDA cooling thermostats of the C/K series with the P control head, in Ultra-Kryomats and also in the process thermostats. The cooling capacity is quasi-proportionally set according to the controller output. This produces energy savings of 7 % as opposed to standard cooling that uses cooling and counter-heating. The room is also heated up to a lesser degree. A further saving of energy is done by the automatic cooling which completely switches off the cooling unit if no cooling is required after a certain time. Protection type IP – Pursuant to EN 60529 two numerals assess the electric degree of protection. The first numeral represents the quality of the touch and foreign body protection (dust). The second numeral assesses the protection against water.

Pump characteristic – This is a diagram that shows the function of the delivery head in relation to the flow rate.



Radial pumps – Radial pumps are centrifugal pumps with a running wheel that has a so-called ‘radial’ shape. The non-linear characteristics of a radial wheel differ fundamentally from the characteristics of a peripheral wheel. At lowest feed pressure and highest feed flow rate the highest drive energy is required with the radial shape. Standard pumps for the chemical industry are radial pumps. Radial pumps are especially suited for small feed pressures and high flow rates.

Recommended temperature range – The recommended temperature range, defined by the highest and lowest operating temperature, is the range in which a bath liquid in a thermostat can be used accurately and reliably over a long period of time. The indicated values result from extensive laboratory tests but must always be interpreted as a compromise between the requirements of the thermostating tasks and possible undesirable side effects. Towards the lower value the bath liquid becomes more viscous, affecting temperature stability, pump output and cooling capacity. In the upper range there is an increased tendency to vaporisation and the production of smells. The values shown are realistic and honest, and keep side effects within acceptable limits. Provided other conditions are acceptable it is desirable to select a liquid that is not used at the limits of its indicated temperature range.

Reduced viscosity (viscosity coefficient) – The specific viscosity based on the concentration C of the dissolved substance.

Refrigerant – Operating material of the cooling process that is located in the closed refrigeration system. The compressor sucks it from the evaporator, where it changes to gaseous condition under heat absorption. On the warmer side of the evaporator the medium cools down through heat absorption. On the high pressure side of the compressor the cooling medium is liquefied in the condenser/heat exchanger under heat transfer. The condenser/heat exchanger is water- or air-cooled.

Refrigerant – This is used in the circuit of the cooling unit and extracts the heat of the thermostating liquid when the compressed gas expands in the evaporator. LAUDA exclusively uses refrigerants with ODP = 0 that cannot cause any harm at all to the ozone layer (ODP = Ozone Depletion Potential).

Refrigeration system – See refrigerant. Relative viscosity – The ratio of the dynamic viscosity ç of the solvent to that of the solvent çs. In the case of severely diluted solvents, this corresponds almost to the ratio of the kinematic viscosities.

Resolution of indication – This mostly relates to the actual value of the digital temperature display and gives the temperature difference between two consecutive figures. In the case of thermostats with the E 100 control head it is 0.1 °C, and for thermostats with the E 200 and E 300 control heads it is 0.05 °C. For the C/K and Ultra the resolution of indication can be adjusted to 0.01 °C or 0.001 °C.

Reverse CMC – Reverse CMC is the determination of CMC by automatically reducing surfactant concentration. This measuring method is based on a LAUDA patent. It is faster and offers significant advantages in handling compared to other methods.

Reverse flow protection – Used when thermostating open external baths with a pressure/suction pump or Duplex pump and prevents overflowing after switching off the thermostat. The reverse flow protection is screwed instead of the metal tube connections onto the pump outlets and is electrically connected to the control head of the C/K series or the Ultra series. The liquid circuit is ventilated by means of a solenoid valve when the thermostat is switched off, the liquid column breaks and cannot flow back.

Ring/Plate tensiometers – Measure the force with which a lamella attacks a Du Noüy ring or Wilhelmy plate. This is used to calculate the surface/ interfacial tension between liquid phases. Ring/plate tensiometers are also used for dynamic contact angle measuring and CMC measuring with software controlled burettes. Risk analysis – The risk analysis has to be generated by the manufacturer of the temperature control unit. The analysis serves to determine the dangers in connection with the unit with reference to the provided operating conditions. Lay-out and construction of the temperature control unit take place in consideration of the risk analysis. As to the remaining dangers which cannot be covered through technical solutions, as well as measures required from the operator, the manufacturer has to inform the operator through indications in the operating manual, and if necessary through mounting alert labels on the temperature control unit.


Safety classes – It is possible to use non-flammable or flammable bath liquids with thermostats. The relevant safety-related requirements are given in DIN EN 61010-2-010. We correspondingly make a distinction between the NFL (non-flammable) classes with built-in overtemperature protection that is exclusively for non-flammable liquids (thermostats of the LAUDA Class A) and FL (flammable) with adjustable overtemperature protection and low level protection for flammable liquids (all other LAUDA thermostats).

Schulz-Blaschke (IV value according to Schulz-Blaschke) – Serves the purpose of the approximate calculation of the intrinsic viscosity of celluloses, polyolefines and others. K1 is an additional constant dependent on polymer.

Secondary side/heat transfer medium side – Denominates the side of the temperature control unit from which the heat transfer medium is flown through. Heat transfer mediums (thermal oil, water) are chosen according to the operating temperature range and their respective application. SelfCheck Assistant – This is a special feature of the LAUDA Proline. The

SelfCheck Assistant checks all parameters before the actual start of operations and especially the switch-off methods of the heater control. The alarm or error messages are shown in clear text on the display. In addition, the system registers not only operating failures such as low level, but also points out the maintenance method such as cleaning of the cooling grid.

Setting resolution – The difference between two consecutive set values with digital set value setting. In the case of analogue set value adjustment with a digital display (C-S, K-S) it should be noted that it is possible to get a significantly higher resolution with a quasi-continuous set value encoder in addition to the setting resolution of the digital display under certain circumstances.

Slave controller – See external control.

SmartCool System – SmartCool System Offers greater cooling output, lower temperatures and the highest precision. LAUDA Proline cooling thermostats have a microprocessor-controlled cooling management – unique in this class. The intelligent cooling control increases or reduces cooling in perfect accordance with the required operating status. Furthermore, the automatic compressor control switches the compressor on – but only if it is really needed.

Solomon-Ciuta formula (Solomon-Ciuta) – Serves the purpose of the approximate calculation of the intrinsic viscosity of PMMA and others. No additional polymer characteristic data required.

Solvent – When changing from one bath liquid to another it is absolutely essential to clean the internal parts of the thermostat, the tube connections, as well as the external system. For this reason suitable solvents are listed for each bath liquid. In order to protect the environment it has however proved satisfactory in most cases to empty the thermostat completely and then to fill it with water with the addition of a surfactant, e.g. a commercially available detergent, and to heat it to approx. 80 °C followed by draining (not applicable with USH 400, Integra and WK). Ideally this operation should be repeated.

Sound pressure level – Sound pressure level is the measure for the sound radiation according to DIN EN ISO 11200. In contrast to the acoustic power level, the pressure level is always assigned to a defined distance. In practice both quantities are stated in dba.

Specific heat capacity – Specific heat capacity is the amount of thermal energy that is required for a temperature increase of 1 °C in a mass of 1 kg. Specific viscosity (relative viscosity increase) – The relative viscosity minus one.

Standards – The safety stipulations for electrical laboratory equipment, and especially also those for thermostats, have been stipulated in the European standards EN 61010-1 and EN 61010-2-010, replacement for DIN 12879, among others. The terms and the stipulation of characteristic data is given in DIN 58966 Part 1 and Part 2 which are currently being revised and will shortly be replaced by DIN 12876-1 and DIN 12876-2.

Surface age – The age of a surface since its formation. In bubble pressure tensiometry, this is the period from the beginning of bubble formation to the hemispherical shape of the bubble. In drop volume tensiometry, this is the period between the formation and the separation of a drop.

Surface tension – The interfacial tension between a liquid and any gas.

Surfactant – An interfacially active substance. The reason for this activity is an asymmetric structure of the surfactant molecule, consisting of a hydrophobic (water-repelling) part and a hydrophilic (water-soluble) part. The interfacial tension is reduced by the adsorption of these molecules at the interface. Suspension – A disperse system, i.e. a fine, but not molecular distribution of a solid body in a liquid.

System pressure – This is the pressure which is produced by pump pressure, vapour pressure at operating temperature and overlay pressure in the heat transfer medium system. Please pay special attention to the maximum system pressure because all components that are flown through by the heat transfer medium have to be suitable for the maximum system pressure (see pressure equipment directive).



Temperature control unit (TCU) – This is a comprehensive term for differently laid out heating or cooling systems that in a defined working temperature range can control temperature of the consumer by means of a liquid.

Temperature controller – Temperature controller is an active component that compares at least one temperature actual value with one setpoint, and depending on the deviation (see control deviation) outputs an adjusting command (see control variable). This so-called ‘adjusting command(s)’ acts on the so-called ‘final control element(s)’ which also actively triggers a measure that acts against the deviation. Temperature controllers can act purely mechanically (for example the so-called ‘heating unit thermostat’) or electronically – be set up analogue or digitally. Often several operating modes are combined.

Temperature stability – Half of the temperature difference between the highest and lowest temperatures which are measured for a specific set value after attaining a stable value within 30 minutes in one thermostat. The details are given at 70 °C (using water) for a heating thermostat and at -10 °C (using ethanol) for a cooling thermostat.

Through-flow cooler – Through-flow cooler is a mechanical or otherwise cooled heat exchanger, where a fluid positively flows through the system. The cooler mainly serves as a cooler for the fluid that is flowing through. Usually the positive flow is generated by a pump.

Through-flow coolers – Add-on coolers which are switched into an external circuit and upgrade the heating thermostats to heating/cooling thermostats. They are on the one hand used to replace water cooling, and on the other hand to reach lower temperatures (down to -40 °C with the DLK 45).

Through-flow heater – Through-flow heater is an electrical or otherwise heated heat exchanger, where a fluid positively flows through the system. The heater mainly serves as a heater for the fluid that is flowing through. Usually the positive flow is generated by a pump.

Two-circuit cascade refrigeration – This is a cascade connection of two refrigeration systems with cooling mediums (see refrigerant) of different thermodynamic properties. Two-circuit cascades with compression refrigerating processes are used at working temperatures below -50 °C. The first cascade (high-temperature stage) produces temperatures of about -35 °C in the evaporator. On the warm side of the evaporator the cooling medium of the second stage (low-temperature stage) condenses at about -30 °C and vaporises at about -90 °C, and is cooling the heat transfer fluid to about -80 °C.



Ultra thermostats – Heating thermostats that are used as bath/circulation thermostats or as pure circulation thermostats with a spatial separation between the bath section and the control unit. This makes possible remote control and reading. The bath for the corresponding application is placed under a fume hood while the control unit is not.

Ultra-Kryomat – A floor-mounted cooling thermostat as a bath/circulation thermostat, available in three different levels as the RUL, RUK and RUK-S classes. These differ according to their cooling and pump outputs. Usable depth – The liquid depth available in the bath thermostat for direct thermostating.



Vario pump – A pressure pump that can be set on a corresponding menu to the various capacity levels concerning flow rate and discharge pressure. This makes possible optimum adaptation to the corresponding application. The LAUDA Vario pump in the Ecoline has five selectable output steps.

Varioflex pump – Varioflex pump is a new centrifugal pump with a pressure and a suction level driven by the same motor. Its pump output can be optimally adjusted in 8 stages to the bath volumes and size via menu. Thanks to its low energy input into the bath and its special plastic, it is suitable for continuous operation at very high temperatures. It is vibration decoupled, therefore low-noise. An additional safety advantage is offered by the Varioflex pump’s patented low-level protection (DGM). By the pressure/suction pump the bath liquid is conveyed from the pressure level into the circulation, the suction level sucks the liquid back into the thermostats. Like the pressure pump, the pressure/ suction pump can also be used for a closed circuit. Compared to the pressure pump, it has the advantage that the pressure in the external circuit falls from positive values (pressure) to negative values (suction) and is almost zero in the external system. This means that even pressure sensitive glass vessels can be thermostated. In addition, by using a pressure/suction pump an open external circuit (a bath container with constant level device) can also be connected. This is not possible with only a pressure pump, as this only conveys the liquid into the bath. However, a further suction stage is required for conveying the liquid from the bath back to the thermostat. The Varioflex pump is available as a high power model as a pure pressure pump for special devices with higher baths.

Viscosity – Properties of a substance (in this case: of liquids) to flow and become irreversibly deformed under the influence of a stress. Flow energy is converted into warmth. Viscosity index (for mineral oil products) – Calculated from the viscosities measured at two different temperatures (40 and 100 °C) according to ISO 2909 and ASTM D 2270. Is a standard for the thermal behaviour of various oils. The higher the viscosity index of an oil is, the less it changes its viscosity at various temperatures.

Viscosity, kinematic – Viscosity refers to the flow behaviour of a liquid that can range from thin to highly viscous. Viscosity depends very largely on temperature. It is a measure of the internal friction between adjacent liquid layers at different velocities. Viscosity affects the characteristics (temperature control, pump output) of a thermostat and is therefore particularly important.

Volumetric expansion – The volume change refers to the increase or decrease of the liquid volume at a certain operating temperature with reference to an initial temperature of 20 °C. The liquid volume to be considered includes both that inside the thermostat itself and also that in the external circulating system.



Washburn method – The contact angle is calculated from the weight increase over time of powders in contact with liquids.

Wilhelmy plate – Standardized plate usually made of a platinum alloy. It is used to measure surface tension with a ring/plate tensiometer. The material of the plate is selected so that its contact angle to the test liquid is equal to zero. Optimal cleaning, e.g. by a Bunsen burner, is essential.

Wilhelmy plate method – Used to measure the surface tension using a standardized plate with a ring/plate tensiometer. The plate is moved towards the surface until the meniscus connects with it. The surface tension is calculated from the resulting force. Due to uncertain wetting behaviour, the plate can only be used for interfaces under certain limitations.

Working temperature range – The temperature range which can be reached at an ambient temperature of 20 °C by the thermostat alone and with the exclusive use of electrical energy and without any other help. In the case of a heating thermostat the working temperature begins approx. 3 °C above the so-called intrinsic temperature, which again can lie distinctly above room temperature, and ends at the upper limit of the operating temperature. This is different in all Ecoline heating thermostats equipped with a Vario pump. At output step 1 the energy input is less than the heat of evaporation, so the intrinsic temperature is below room temperature and thus it is already possible to work directly from ambient temperature without water cooling with an uncovered bath.

Working temperature range, extended – The temperature range that can be reached when using a factory-fitted cooling coil when working with mains water.


Applied Thermal Control Ltd.
39 Hayhill Industrial Estate, Barrow upon Soar, Leicestershire, LE12 8LD.
Telephone: +44 (0) 1530 83 99 98
E-Mail: sales@app-therm.com
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