Troubleshooting - Fluke 7008 User Manual

The displayed process temperature is in
error and the controller remains in the
cooling or the heating state at any set-point
value
The controller controls or attempts to control
at an inaccurate temperature
1.3) for assistance.
Possible causes may be either a faulty
control probe or erroneous data in memory.
•
The probe may be disconnected, burned
out, or shorted.
•
Check that the probe is connected
properly. The probe may be checked
with an ohmmeter to see if it is open or
shorted. The probe is a thermistor. The
resistance should read approximately 3
kohms between pins 3 and 4, 12 kohms
between pins 1 and 4, and 9-11 kohms
be- tween pins 1 and 3 at room
temperature (25 °C). If the probe
appears to be defective, contact an
Authorized Service Center (see Section
1.3) for assistance.
•
If the problem is not the probe,
erroneous data in memory may be the
cause. Re-initialize the memory as dis-
cussed in the problem 'The display
flashes "cutout" and an incorrect process
temperature'. If the problem remains, the
cause may be a defective electronic
component, contact an Authorized
Service Center (see Section 1.3) for
assistance.
The controller operates normally except when
controlling at a specified set-point. At this set-
point, the temperature displayed does not
agree with the temperature measured by the
user's reference thermometer to within the
specified accuracy. This problem may be
caused by an actual difference in
temperature between the points where the
control probe and thermometer probe
measure temperature, by erroneous bath
calibration parameters, or by a damaged
control probe.
•
Check that the bath has an adequate
amount of fluid in the tank and that the
stirrer is operating properly.
•
Check that the thermometer probe and
control probe are both fully inserted into
the bath to minimize temperature
gradient errors.
•
Check that the calibration parameters
are all correct according to the Report of
Test. If not, re-program the constants.
The memory backup battery may be
weak causing errors in data as described
in the problem: 'The display flashes
"cutout" and an incorrect process
13

Troubleshooting

13.1 Troubleshooting
13-3