7. MAINTENANCE OF TRACEABILITY AND RECALIBRATION
Page 153
© 2005 - 2007 DH Instruments, a Fluke Company
Calculate the difference between the two following:
PG7601 avg. temp. [ºC] – reference avg. temp. [ºC] =
Δ
avg. temp [ºC]
Calculate the resistance corresponding to
Δ
avg. temp using the slope of the
PG7601 PRT following:
Δ
avg. temp [ºC] x PRT slope [
Ω
/
°
C] =
Δ
resistance [
Ω
]
Calculate the new offset by adding the
Δ
resistance to the previous offset (the
previous offset is the previous value of <
RZ>
in the PG7000 Terminal display or
<Resistance at 0 ºC>
in
ADCS Tools
,
[Maintenance]
,
[Calibration]
,
[Piston-
Cylinder]
(see Figure 65):
previous offset [
Ω
] +
Δ
resistance [
Ω
] = new offset [
Ω
]
The new offset should be entered into the system following the procedure
described below.
Updating piston-cylinder temperature sensor information
The offset value of the piston-cylinder mounting post platinum resistance
thermometer may change from calibration to calibration. The new offset value
determined above must be entered into the ADCS-601-AF system so that it is used
in its calculations. For additional information on PG7601 characteristics and how
they are stored in the PG7601 platform, see the PG7000 Operation and
Maintenance Manual.
ADCS Tools
has the capability to to view or edit the value of the PG7601’s
mounting post PRT offset and slope. Use
[Maintenance]
,
[Calibration]
,
[Piston-Cylinder]
(see Figure 65).
ADCS Tools
must be ON for the
[Maintenance]
menu to be accessible. The PRT calibration data is displayed
and edited in the
[Mounting Post PRT]
panel. Check that the correct PRT is
shown by verifying its serial number against the serial number shown in the
panel label. To change the active PRT use
[Setup]
,
[Configuration]
,
[PG]
.
Enter the new offset value in by clicking on the value and entering the desired
value. The field is labeled
<Resistance at 0 ºC>
as this is a conventional term
for platinum resistance thermometers but the resistance at ambient temperature
is used as the offset because the RPT is only used in the limited range of 15 to
35 ºC.
The slope value is not normally edited as it is a physical constant for the type of
PRT used (see Section 7.3.4.1)
When all changes are complete, press the
[Save Changes]
button to cause
ADCS
Tools
to store the entered values permanently in PG7601 Platform memory.
Use
[Close]
to leave the form without making any changes.
Use
[Reload]
to reload the form with the values that are in the PG7601 Platform
memory. This feature can be used to verify the data entered after
[Save
Changes]
has been pressed.
