Figure 2.7 Example Thermistor Resistance Vs. Temperature - ILX Lightwave LDT-5900 Series User Manual

High power temperature controller, precision temperature controller

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supply current selection depends on the thermistor operating temperature range

and the required temperature resolution. A general rule of thumb for a 10 k

thermistor is to use the 10 A range for temperatures between -30

and the 100 A range for temperatures between 10

Select the thermistor sense current of 10 A or 100 A through the front panel

sensor menu. Using 10 A as the sense current allows you to use a maximum

thermistor resistance of 600 k . The 100 A setting allows a 60 k

To ensure proper current and thermistor selection, certain principles must be

considered:

• To ensure measurement accuracy, the voltage across the thermistor must not exceed 6 V.

• To improve control responsiveness and accuracy, the thermistor voltage variations that

In the example shown in Figure 2.7, the thermistor resistance is 25 k at 20

Deviations of 1

the 10 A setting, there is 20 mV of feedback to the control circuit. Using the 100

A setting provides 200 mV of feedback. The larger feedback signal means that

the temperature is more precisely controlled.

Notice also that the lower slope of the curve at the higher temperatures results in

a smaller feedback signal. It may be necessary, if you are controlling to higher

temperatures, to use a thermistor with a different curve.

01_10

result when the load temperature deviates from the setpoint must be as large as possible.

The importance of maximizing voltage variation is shown in Figure 2.7, which shows

resistance as a function of temperature for a thermistor. The values shown were selected

for simplicity in this example, and may not reflect real thermistor values.

C from 20