Alpes Lasers . TC-3 Uživatelský manuál stáhnout pdf (Strana 23)

TC-3 Temperature Controller User’s Manual · Page 23

Working With Thermistors

The TC-3 is designed to work with negative temperature coefficient

(NTC) thermistors, such as the BetaTHERM 10K3A1 thermistor. A

thermistor works by translating temperature into resistance, with

resistance decreasing as temperature increases (hence the ‘negative

coefficient’).

Here is a typical response curve of a thermistor:

-10.00 10.00 30.00 50.00 70.00 90.00 110.00

10000

20000

30000

40000

50000

Temperature (°C)

Resistance (Ω)

Typical Resistance vs. Temperature Graph

As can be seen be the graph, the resistance of the thermistor drops

very quickly. In the typical control range (0°C to 40°C), typical 10K

thermistors offer good sensitivity to changes in temperature, and this

is the range in which most 10K thermistors are typically used. 10K

thermistors can be used at much higher temperatures, but will suffer

poorer temperature stability performance because of the lower

sensitivity. When evaluating the performance of a thermistor, it is

important to understand the resistance sensitivity of the thermistor at

your application temperature, which varies greatly by temperature and

thermistor types.

The TC-3 supports operation using a 10μA or 100μA constant current

source, which limits the upper control range to 450kΩ, 45kΩ, and 4.5kΩ,

respectively. To minimize noise and maximize stability, you should

select highest current while still allowing you full operation across your

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Alpes Lasers . TC-3 Uživatelský manuál Strana 23