5.
MAINTENANCE, ADJUSTMENTS AND CALIBRATION
Page 177
© 1998-2008 DH Instruments, a Fluke Company
The normal calibration procedure of the PRT is to remove it from the PG7000
mounting post and determine its offset (actual resistance at 0
°
C) by calibration.
To remove the PRT from the PG7000 mounting post, follow the instructions
provided in Section 5.2.1.5, Mounting Post PRT Removal.
The value of resistance at 0
°
C and the slope, if desired, can be edited to reflect
the new calibration by pressing
[SPECIAL]
and select
<4PCT>
.
Though the ambient temperature sensor and piston-cylinder module
temperature sensor are of the same technology and read in the same manner, the
recommended calibration procedures differ reflecting the difference in measurement
uncertainty needed. The ambient temperature sensor (whose measurement
uncertainty is
±
1
°
C) is calibrated by simple offset relative to an external reference
measurement (see Section 5.2.1.3).
OPERATION
To view the output of the piston-cylinder module temperature sensor, press
[SPECIAL]
and select
<4PCT>
,
<1view>
. The display is:
1.
Current reading of the piston-cylinder module
temperature sensor converted to degrees
Centigrade.
2. Indication that this is a piston-cylinder
module temperature display.
3.
Current value of the resistance slope relative
to temperature.
4.
Current value of the offset at 0 °C in ohm.
19.951 °C PCT
RZ100.003
Ω
S0.3896
To adjust the values of
RZ
and/or
S
, press
[SPECIAL]
and select
<4PCT>
,
<2cal>
to access a screen in which the values of
RZ
and
S
can be edited.
From here, press
[ESCAPE]
and select
<4PCT>
,
<1view>
to view the piston-
cylinder module temperature reading with the edited calibration coefficients applied.
Mounting Post PRT Removal
To remove the mounting post PRT:
Remove the piston-cylinder module from the mounting post and replace with
the ORANGE storage plug.
Disconnect the PG7000 Platform from the PG7000 Terminal.
Invert the PG7000 Platform so that the bottom of the platform is up.
Support the platform so that it does not tip over. A simple solution is to place
the platform upside down on a sturdy box which is smaller than the outside
platform dimensions and is also tall enough to allow the mounting post to
be suspended.
Remove the six socket head screws (3 mm) around the perimeter of the
platform.
Lift the platform up and carefully disconnect the sensor leads at their board
connections, noting their locations.
Loosen
-
but do not remove
- the four socket head screws (3 mm) located on
the PRT/cable pass through plate. The plate is located on the inside of the base.
Slide the PRT out of the mounting post.