Glossary constant temperature equipment

Glossary constant temperature equipment

ACC range (Active Cooling Control): according to DIN 12876

This is the working temperature range during operation with an active cooling unit. The working temperature range is equal to the ACC range in all LAUDA devices.

Ambient temperature range

This is the permissible temperature range of the environment in which the device works properly. It is 5…35 °C for all LAUDA devices contained within this brochure with the exception of the ECO, Integral and the WK devices, where the latter is extended to 40 °C. This is particularly important with respect to industrial applications.

Bath depth

Is the overall dimension from the upper edge to the bottom of the bath.

Bath opening

Is the usable surface available for direct thermostating, as a rule over the entire usable depth.

Bath thermostat

Is a thermostat which is equipped with a bath capable of holding the object to be thermostated. The built-in circulation pump is used to mix the bath liquid, but can also be used to convey the liquid through a closed external circuit, e.g. the connection of through-flow coolers, if required.

Bath volume (also filling volume)

Is the volume of the bath liquid that is required for the appropriate operation of the thermostat in the bath. The required minimum volume and the permitted maximum volume are usually given. The difference is the expansion volume, which must absorb the heat expansion of the bath liquid. The expansion volume is especially large with process thermostats.

Bath/circulation thermostat

Is a bath thermostat with a circulating pump for closed or open external circuits.

Calibration thermostat

Is a bath thermostat with especially high temperature stability and especially consistent spatial temperature distribution. It is used mainly for the calibration and adjustment of test pieces in the bath.

Circulation chiller (also circulating chiller)

Are special cooling thermostats designed as circulation thermostats without a freely-accessible bath. Thanks to their construction, they are independent devices which are frequently used as a replacement for the cooling with mains water.

Circulation heat exchanger

Is an add-on cooler which, via a heat exchanger, uses an existing primary cooling circuit to cool various external systems.

Circulation thermostat

Is a thermostat through which the bath liquid is conveyed through an open or closed external circuit.

Clear-view thermostat

Is a bath thermostat with transparent front and back to enable viewing of an object to be thermostated, usually a viscometer. Bath thermostats with transparent polycarbonate baths are known as thermostats with transparent bath.

Cooling cascades

If temperatures below -50 °C are to be produced with compressor cooling units, 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 approx. ambient temperature to -40 °C, for example. The low-temperature stage provides the final temperature of -90 °C, for example.

Cooling output

Is the effective output available in a cooling thermostat or circulation chiller. Losses caused by the circulating pump and invasive heat have already been deducted.

Cooling thermostat

Is a thermostat whose working temperature range is below the ambient temperature.

Discharge pressure

Is the pressure of the circulation pump of a thermostat directly at the pressure nozzle, measured with water. In the tables, the maximum discharge pressure is given at flow rate zero. The diagrams illustrate the discharge pressure is dependent upon the flow rate.

Discharge suction

This is the suction of the circulation pump (Varioflex or Duplex pump) directly at the suction nozzle, measured with water. In the tables, the maximum suction is given at flow rate zero. The diagrams illustrate the discharge suction is dependent upon the flow rate.

Display resolution

Is given with regard to the digital temperature display of the actual value, and displays the temperature difference between two subsequent numbers.

EasyUse operation (Proline)

Drain taps, castors and handles for increased mobility, double pump connections for the parallel connection of two external systems, switching of the circulation (bypass), removable Command remote control, and quick change of the required interfaces.

External control

The temperature of the thermostat is controlled via a temperature probe connected to the external system. The set value is compared with the actual value in the external system and readjusted within the thermostat. Depending on the operating temperature, insulation losses and exothermia, the bath temperature can be considerably above or below the set value. External control ensures that the bath temperature and applica-tion temperature are constant.

Flow rate

Is the volume of liquid conveyed per time unit by the circulation pump, measured with water. In the tables, the maximum flow rate is given at counter pressure zero. The diagrams illustrate the discharge pressure is dependent upon the flow rate.

Heating and cooling thermostat

Is a thermostat whose working temperature range is above and below the ambient temperature and which can both heat and cool.

Heating capacity

This is the maximum electrical capacity of the installed heater at the given nominal voltage. The heating capacity of LAUDA thermostats may be controlled if required.

Heating thermostat

Is a thermostat whose working temperature range is above the ambient temperature and which can only heat.

Immersion cooler

Is an add-on cooler which is connected by means of a flexible tube to a cooling coil for immersion in any bath or vessel.

Immersion thermostat

Is a thermostat which can be combined with any bath. It is attached to the side of the bath or on a stand by means of a screw clamp.

Interface, analogue

Is used to input the set value of the temperature/to output temperature values or other values in analogue form, usually as a reference signal with voltage (0…10 V) or current (0/4…20 mA). Relevant LAUDA interfaces are adjustable and scalable.

Interface, digital

Is used to exchange digital data, mainly set and actual temperature values. The RS 232 interface is of a serial type and allows a point-to-point connection. This means that only two participants can communicate at a time with each other via the interface. The RS 485 interface is an addressable interface to which up to 32 participants with their own address may be connected.

International protection, IP

As per EN 60529. The first digit indicates the protection against contact and foreign objects, whereas the second digit indicates protection against water. For example, IP 32: 3 stands for protection against contact with dangerous parts located inside with a tool of greater than/equal to 2.5 mm diameter and up to 100 mm in length. 2 stands for protection against dripping water at angles of 15 °. The assessment is carried out as per EN 61010-1. The LAUDA range only provides IP information for process thermostats and circulation chillers.

Intrinsic temperature

Is the operating temperature of a heating thermostat attained when the thermostat is switched off. It depends on the pump capacity, the heat transfer liquid used and the insulation of the thermostats. The working temperature range only starts approx. 3 °C above the intrinsic temperature.


Is a floor-mounted heating and cooling thermostat in three different levels with various cooling and pump capacities.

Operating temperature range

This is the temperature range defined by the lowest and highest permissible operating temperature. 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.

PowerAdapt System (Proline)

The maximum possible heating capacity is used as far as is permitted by the net. Advantage: up to 3.5 kW heating capacity even with cooling thermostats, shorter heating times and no overloading of the net. The patented LAUDA heater control minimises the loading effects on the laboratory’s voltage network. Moreover, the maximum power consumption can be reduced to 10 A as required.

Pressure pump

Is used for the circulation of the bath liquid in a closed external circuit and for mixing the liquid within the bath.

Process thermostats (Integral T, Integral XT)

Are circulation thermostats used as heating and cooling thermostats with high cooling, heating and pump capacities. Small volumes of liquid enable quick cooling-down and heating speeds: they are ideal for process technology applications.


Is a bus system with a high signal transfer rate for connecting up to 256 devices and is used mainly in the chemical industry.

Proportional cooling (Kryomats, Process thermostats)

The cooling output is quasi-proportionally set according to the controller signal. This produces savings of around 75 percent compared to standard cooling that uses cooling and counter-cooling. The automatic cooling output adjustment also switches the cooling unit off completely should no cooling be required for a longer period of time.


Is used in the circuit of the cooling unit and extracts the heat of the thermostating liquid when the compressed gas expands and evaporates in the evaporator.  LAUDA only uses refrigerants with ODP = 0 which do not destroy the ozone layer (ODP = ozone depleting potential). In several LAUDA thermostats natural refrigerants are used. Natural refrigerants are naturally occurring, non-synthetic substances. In addition to a ODP of zero they also have a very low GWP (global warming potential).

Resolution setting

Is the difference between two consecutive set values of a digital set value setting.

Safety class

It is possible to use non-flammable or flammable bath liquids in thermostats. The relevant safety-related requirements are stipulated in DIN EN 61010-2-010. According to DIN 12876-1, we make a distinction between class I with the distinction NFL (non-flammable) with built-in overtemperature protection exclusively for non-flammable liquids, and class III with the distinction FL (flammable) with adjustable overtemperature protection and low level protection for flammable liquids.

SelfCheck Assistant (Proline, Integral XT)

The SelfCheck Assistant checks all parameters before the actual start of operations and the switch-off methods of the heater control in particular. The system registers not only alarm or error messages on the display: it also points out scheduled maintenance tasks such as cleaning of the cooling grid.

SmartCool System (Proline)

A special form of proportional cooling combined with a regulated ventilator.

Sound pressure level

Is measured according to the guidelines given in DIN EN ISO 11200 and the basic standards contained therein.


The safety regulations for electric laboratory equipment are stipulated in the European standards EN 61010-1 and EN 61010-2010. The terms and the stipulation of the characteristic data are described in DIN 12876. EMC requirements are stipulated in EN 61356. Depending on the device, further standards may be applied.

Temperature stability

This is half of the temperature difference between the highest and the lowest temperatures which are measured at a specific set value after attaining a stable value for 30 minutes in a thermostat. The details are provided at 70 °C (using water) for a heating thermostat and at -10 °C (using ethanol) for a cooling thermostat.

Through-flow cooler

Is an add-on cooler which can be interconnected in an external circuit and which extends the function of a heating thermostat to that of a heating and cooling thermostat. It replaces water cooling or can be used to achieve lower temperatures (down to -40 °C with the DLK 45/DLK 45 LiBus).

Ultra thermostats

Are heating thermostats used as bath/circulation thermostats or as pure circulation thermostats with spatially-separated bath and control unit. This enables remote control and monitoring.

Usable depth

Is the maximum liquid depth available in the bath thermostat for direct thermostating.

Vario pump (ECO, Integral XT)

Is a pressure pump which can be set to various output stages with regard to flow rate and flow pressure. This enables the optimum adaptation to the corresponding application.

Varioflex pump (Proline)

Is a pressure/suction pump with 8 different pump capacity settings to be connected to open and closed circuits. Its low energy input makes working at the lowest temperatures possible. The Varioflex pump is available in a high-power model as a pure pressure pump for devices with deeper baths. The patented low-level protection (DGM) is an additional safety advantage.

Water bath

Is a heating bath which does not have a pump for active mixing purposes and which is only equipped for use with water.

Working temperature range

This is the temperature range which can be attained at an ambient temperature of  20 °C by the thermostat alone and with the exclusive use of electrical energy and without any other aid. The working temperature range of a heating thermostat begins above the ambient temperature and ends at the upper limit of the operating temperature.