Temperature Equations - Keithley 3700A Series Reference Manual

Series 3700A System Switch/Multimeter Reference Manual
For example, the following remote commands configure temperature function to a custom RTD and
assign it to a 10-channel scan list.
reset()
dmm.func=dmm.TEMPERATURE
-- or 3, or dmm.TEMP_FOURRTD, or 4
dmm.transducer= dmm.TEMP_THREERTD
-- dmm.fourrtd also supported
dmm.threertd=dmm.RTD_USER
-- allowed values are 0 to 0.01
dmm.rtdalpha= 0.003
-- allowed values are 0 to 1.00
dmm.rtdbeta= 0.105
-- allowed values are 0 to 5.00
dmm.rtddelta = 1.51
-- allowed values are 0 to 10,000
dmm.rtdzero= 125
-- default dmm.ON
dmm.offsetcompensation=dmm.OFF
dmm.configure.set("my_rtd_user")
dmm.setconfig("4001:4010", "my_rtd_user")
scan.measurecount=1
buf=dmm.makebuffer(20)
buf.clear()
buf.appendmode=1
scan.create("4001:4010")
scan.scancount=2
scan.execute(buf)
for x=1, buf.n do printbuffer (x,x,buf) end
channel.open("allslots")

Temperature equations

The following topics contain information you can use when making temperature measurements.
•
Thermocouple equation
the coefficients to calculate thermocouple temperature.
•
Thermistor equation
calculate thermistor temperature.
•
RTD equations
calculate the temperature versus resistance readings listed in the RTD reference tables.
Thermocouple equation
The Series 3700A uses the ITS-90 inverse function coefficients for the polynomial to calculate
thermocouple temperature. The Series 3700A measures the thermocouple voltage and then
calculates temperature (in °C) as follows:
Where:
•
t = The calculated temperature in °C.
90
•
c , c
0
•
E = The thermocouple voltage in microvolts (µV).
The coefficients for each thermocouple type are listed in the following tables.
3700AS-901-01 Rev. D/June 2018
(on page 4-33): Documents the ITS-90 inverse function polynomial and
(on page 4-38): Documents the Steinhart-Hart equation, which is used to
(on page 4-39): Documents the Callendar-Van Dusen equation, which is used to
2
t = c + c E + c E + c
90 0 1 2
= The coefficients for the thermocouple type.
, c , c ... c
1 2 3 i
3 i
E ... c E
3 i
Section 4: Basic DMM operation
4-33