Default Rtd Coefficients - Fluke 525A User Manual

Default RTD Coefficients

The USR_DEF function of the calibrator uses the Calendar-Van Dusen equation
for outputting and measuring custom RTDs. The C coefficient is only used for the
subrange –260 to 0 degrees Celsius. Only the A and B coefficients are needed for
the subrange 0 to 630 degrees. The R0 is the resistance of the probe at 0 degrees
Celsius. All of the USR_DEF will be set to PT385 as shown in Table 2-1..
Sub range
USR_DEF1 0 to 630
USR_DEF2 -260 to 0
USR_DEF3 0 to 630
USR_DEF4 -260 to 0
USR_DEF5 0 to 630
If other types of RTDs are required, Table 2-2 shows the coefficients for types
PT391 and PT392. The C coefficient is only used for temperatures below 0
degrees Celsius.
RTD Type
PT392
PT391
The SPRT 25 ohm function of the calibrator uses ITS-90 standard coefficients for
measuring a SPRT. Since the five coefficients are deviations all of them will be set
to 0.
The measuring function of the calibrator is limited to 100 ohms, so it
can not be used for >100 ohm SPRT.
Table 2-1. Default RTD Coefficients
R 0
100
100
100
100
100
Table 2-2. Other Commonly Used RTDs
Coefficient A
3.9848X10-3
3.9692X10-3
Note
Coefficient A Coefficient B
3.908X10-3 -5.8019X10-7
3.908X10-3 -5.8019X10-7
3.908X10-3 -5.8019X10-7
3.908X10-3 -5.8019X10-7
3.908X10-3 -5.8019X10-7
Coefficient B
-5.87X10-7
-5.8495X10-7
Using Output Mode
Using Output Mode
Coefficient C
-5.8019X10-12
-5.8019X10-12
Coefficient C
-4X10-12
-4.2325X10-12
2
2-5