8. GENERAL MAINTENANCE
Page 129
© 2007 DH Instruments, a Fluke Company
8.5.3
DETERMINE THE RO VALUE
R0 is the PRT zero temperature resistance. A separate value must be determined for each
mounting post PRT. R0 is determined by converting the reference temperature to a
resistance and correcting the 4-Wire resistance of the mounting post PRT. For best results,
use the lab temperature in which the FPG will be used. The resistance of the PRT is
adjusted based on the temperature reference value as described in the equation below.
The FPG8601 PRTs use a slope of 0.3896
Ω
/
°
C
instead of ITS90 coefficients.
(
)
T
R
R
Meas
old
3896
.
0
0
0
−
Ω
−
=
Table 48.
Effective Area Calculation Variables
VARIABLE
DEFINITION
R0
OLD
The Ro value of the FPG PRT as determined in the
previous calibration. The current value can be obtain
by following the steps outlined in Section 8.5.4.
Ω
Meas
Measured 4-Wire resistance of the mounting post
PRT. The PRT calibration cable should be connected
to a calibrated DMM to measure this value.
T
The measured temperature of a calibrated temperature
reference.
8.5.4
ENTER THE RO VALUE INTO THE FPG TERMINAL
The R0 values obtained for each PRT must be entered into the FPG Terminal. Use the
following key sequence on the FPG terminal to view or edit the R0 values of either of the
mounting post PRTs.
The R0 values of the mounting post PRTs must be entered into the FPG Terminal.
These values are not maintained or viewed by FPG Tools.
Press
[0 Special]
.
Press
[4 Internal]
.
Press
[3 Std&PRT
Ω
]
.
The R0 value for the upper mounting post PRT will display. Type in the new value and
press
[Enter]
.
The R0 value for the lower mounting post PRT will display. Type in the new value and
press
[Enter]
.
Press
[Enter]
3 more times to step through the remaining screens without modifying the
current values.
Press
[2 Save]
.
