E -04
Increase or decrease the exponentusing the Uand Dbuttons. Once the ex-
ponent is correct, press Enter to store it.
6.4.3 Steinhart-Hart Characterization
Thermistorsare most often characterized using the Steinhart-Hart equation:
rTK expBBTBTBT
o
([])[] [ ]Ω= + + +
−−−
1
1
2
2
3
3
This isthe default probe type. The parameters that appear for this option are
“b0”, “b1”, “b2”, and “b3”. These should be set with the valuesof the corre-
sponding coefficientsthat appear on the thermistor’s calibration certificate.
The coefficientson the certificate may be labeled differently.For instance,
some certificatesgive values for coefficients “a”, “b”, “c”, and “d”. Also, some
certificatesmay give more than one set of coefficients for different equations.
Choose thecoefficients that are given for the equation that is similar to the one
shownabove. The table below showing typical values can help you identify the
proper coefficients.
Some calibration certificates for thermistors giveonly three coefficients. If this
is the case, setthe b0, b1, and b3 p arametersfrom the coefficients on the certif-
icateand set the b2 parameter to 0. Following are some examples showing how
to setthe 1504 parameters from coefficients given on the thermistor calibration
certificate.
Example1:
A thermistor’scalibration certificate gives coefficients a=-4.6853436E00,
1504 Thermometer Readout
User’s Guide
20
1504Coefficients Typicalvalues
b0 -5to -3
b1 3000to 5000
b2 ±9x 10
5
(positiveexponent)
b3 ±9x 10
7
(positiveexponent)
Table 2 Typical Values for Thermistor Coefficients