LM134-LM234-LM334

Application information

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4.6

Sensing temperature

The LM134, LM234, LM334 are excellent remote controlled temperature sensors because

their operation as current sources preserves their accuracy even in the case of long

connecting wires. The output current is directly proportional to the absolute temperature in

Kelvin degrees according to the following equation.

The calibration of the LM134, LM234, LM334 is simplified by the fact that most of the initial

accuracy is due to gain limitation (slope error) and not an offset. Gain adjustment is a one

point trim because the output of the device extrapolates to zero at 0°K.

Figure 10.

Device calibration

This particularity of the LM134, LM234, LM334 is illustrated in the above diagram. Line abc

represents the sensor current before adjustment and line a’b’c’ represents the desired

output. A gain adjustment provided at T2 will move the output from b to b’ and will correct

the slope at the same time so that the output at T1 and T3 will be correct. This gain

1% on the slope because the resistance follows the same temperature variations as the

LM134, LM234, LM334.

is not recommended, metal-film resistors with a drift of less than 20ppm/°C are now

available. Wirewound resistors can be used when very high stability is required.

I

227µV/°K) (T

()

R

set

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