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BS 4745 Togmeter

An instrument to measure the thermal resistance of textiles from 0.5 to 25 mm thick. in accordance with BS 4745 / ISO 5085 using the comparator hotplate principle (Principles of tog testing).

The equipment consists of a forced-air cabinet, a circular hotplate and a selection of two cold plates; one designed to lie on top of the material and apply a known pressure, the other which can be set to a specified height and provide a gap equal to the nominal thickness of the material, while applying sufficient pressure to ensure the material remains in contact with the plates. An electronic controller controls the temperature of the hotplate and displays the measured tog value.

Tog bed

Test procedure

Cut a 330mm diameter sample of the material and condition it for 24 hours at 20C (+/-2) and 65%RH (+/-5) Place the conditioned sample on the hotplate. Plug one of the cold plate units into the socket. Close the door of the instrument.
The display will indicate the hotplate temperature as the rig comes to equilibrium, then will switch to displaying measured tog value. In the case of an open test, it is then necessary to subtract an 'air tog' value (determined by a bare-plate run) from the result to get the net tog of the product. Each test will take about 3 hours.

Air conditioning

BS4745 requires that the environment meets the general conditions of temperature and humidity for testing textiles. However variations in the room temperature during the test can affect the result, and it is important that the temperature remains stable during the test. If the room temperature varies cyclically due to the operation of a thermostat, then the indicated tog value should be observed over at least one full cycle in order to know the range of variation this is causing.


For sales information plese refer to Wira Instrumentation who are manufacturing this isntrument.

Technical details

This is a precision instrument requiring minimal calibration and capable of 1% accuracy given suitable environmental controls.
Hotplate temperature 33C 0.1
Heater over-temperature protection
Absolute temperature sensing by chopper stabilised platinum resistance sensor with 0.001K precision.
Differential temperature sensing by chopper stabilised differential thermocouples.
Digital processing of thermal resistance calculation.


Test time approx 3 hours.
Hotplate powered from a stabilised 12V DC supply.
All system temperatures over entire measurement cycle can be recorded for validation.
Compliant with CE regulations for electrical safety and EMC.