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37.1.8 All temperature values in Table 37.1 are based on an assumed ambient temperature of 25°C
(77°F). However, with correction of temperature measurements, tests may be conducted in other
ambients as described in Table 37.2.
37.1.8 effective April 13, 1993
Table 37.2
Temperature measurement correction
Table 37.2 effective April 13, 1993
Ambient temperature rating of
converter or inverter Test ambient temperature Correction of observed temperature
1. 25°C (77°F) Range of 10 – 40°C See note a, item A
(50 – 104°F)
2. Range of 25 – 40°C (77 –
104°F)
Range of 20 – 40°C See note a, item B
(68 – 104°F)
3. Above 40°C (104°F) Rated ambient c
See note b
a
Correction of temperature, as determined by item A or B below, shall not exceed the temperature limit specified in Table 37.1.
A. An observed temperature is to be corrected by addition if the test ambient temperature is lower then 25°C
(77°F) or by subtraction if the test ambient temperature is higher than 25°C (77°F) of the difference between 25°C
(77°F) and the test ambient temperature.
B. An observed temperature is to be corrected by addition (if the test ambient temperature is lower than the rated
ambient temperature) or by subtraction (if the test ambient temperature is higher than the rated ambient
temperature) of the difference between the rated ambient temperature and the test ambient temperature.
b
Allowable tolerances are:
Minus – not less than 5°C (9°F) below rated ambient.
Plus – not specified.
c
If the test ambient temperature equals rated ambient, no correction is to be made, and an observed temperature shall not
exceed the temperature limit specified in Table 37.1. If the test ambient temperature is other than the rated ambient, correction
is to be made as described in item B of note a.
37.1.9 Thermocouples are to consist of wires not larger than 24 AWG and not smaller than 30 AWG.
When thermocouples are used in determining temperatures in electrical equipment, it is common practice
to employ thermocouples consisting of 30 AWG iron and constantan wire and a potentiometer-type
instrument. Such equipment is to be used whenever referee temperature measurements by
thermocouples are necessary. The thermocouples and related instruments are to be accurate and
calibrated in accordance with good laboratory practice. The thermocouple wire is to conform with the
requirements for special thermocouples as listed in the table of limits of error of thermocouples in
Temperature Measurement Thermocouples, ANSI MC96.1-1982.
37.1.9 revised October 15, 2004
37.1.10 A thermocouple junction and the adjacent thermocouple lead wires are to be held securely in
good thermal contact with the surface of the material of which the temperature is being measured. Usually
adequate thermal contact will result from securely taping or cementing the thermocouple in place but, if a
metal surface is involved, brazing or soldering the thermocouple to the metal may be necessary.
OCTOBER 15, 2004UL 45854
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