User's Manual

Thermistor Range
34 LDT-5525
CHAPTER B

thermistor inputs of the LDT-5525. The LDT-5525's measurement system will
over-range when the input voltage exceeds about 4.5 volts. Figure B.1
graphically shows the lower temperature and upper voltage limits for a typical 10
K thermistor. (A 10 K thermistor has a resistance of 10 kΩ at 25
o
C). The practical
temperature ranges for a typical 10 K thermistor with the LDT-5525 are given in
Table B.2, below. These temperature ranges may vary from thermistor to
thermistor, even though both thermistors are nominally 10 K. This is due to
manufacturing tolerances in the thermistor, and is compensated for by
determining C1, and C2 (calibrating the thermistor). The practical temperature
ranges for a 10 K thermistor are also shown as solid bars at the bottom of Figure
B.1.
Table B.2 10K Thermistor Temperature Range
Figure B.1 Thermistor Temperature Range
SENSING CURRENT TEMPERATURE RANGE
10 µA -30 to 30
o
C
100 µA 10 to 70
o
C
THERMISTOR
VOLTAGE
5.00
4.00
3.00
2.00
1.00
0.00
-60
-40
-20
02040
60
80
100
(USING TYPICAL* 10 k @ 25 C THERMISTOR)Ω
o
DEGREES C
10 Aµ
100 Aµ
* ILX default values for C1 and C2
4.50
- Denotes practical range with typical 10K thermistor
- Denotes measurable range with typical 10K thermistor