Fluke 2680A User Manual page 239

Using the Custom-385 RTD with Other Platinum RTDs
Although the Custom-385 RTD linearization uses a β and δ from a 385 RTD,
other RTD types can be used. The Custom-385 linearization will compensate for
the change in α, but errors will be introduced due to the difference in the δ and β
coefficients of the RTD and the fixed coefficients. Figure D-2 shows the accuracy
envelope for a 375 RTD. Because of the error introduced by the approximation
and the difference in δ it is recommended that the use of the 375 RTD be limited
to temperatures between -100 °C and 300 °C. Figure D-3 shows the accuracy
envelope for a 391 RTD and Figure D-4 shows the accuracy envelope for a 392
RTD. Due to errors introduced by the approximation and the difference in δ it is
recommended that the use of the 391 RTD and 392 RTD be limited to
temperatures between -100 °C and 600 °C.
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-100
Accuracy Envelope: Custom RTD, 375 Probe
1 Year Slow: 18-28 Degrees C
Alpha: 0.00375 Delta: 1.605 Beta: 0.16
FAI
PAI
-50 0 50
Temperature - Degrees C
Figure D-2. 375 RTD
100 150 200
Appendices
RTD Linearization
250 300
alg62f.eps
D
D-3