Fluke 7038 User Manual page 67

7037/7038/7040/7041 Calibration Bath
User's Guide
66
Problem
The display flashes "cutout" and
an incorrect process temperature
The displayed process tempera-
ture is in error and the controller
remains in the cooling or the
heating state at any set-point
value
The controller controls or at-
tempts to control at an inaccurate
temperature
Causes and Solutions
The problem may be that the controller's voltmeter circuit is not func-
tioning properly. A problem could exist with the memory back-up bat-
tery. If the battery voltage is insufficient to maintain the memory, data
may become scrambled causing problems. A nearby large static dis-
charge may also affect data in memory.
The memory may be reset by holding the "SET" and "EXIT" keys
down while power to the controller is switched on. The display shows
"—init—" indicating the memory is being initialized. At this point, each
of the controller parameters and calibration constants must be repro-
grammed into memory. You can obtain the calibration constants from
the test results sheet of the calibration report.
If the problem reoccurs, the battery should be replaced. Contact an
Authorized Service Center for assistance. If initializing the memory
does not remedy the problem, there may be a failed electronic compo-
nent. Contact an Authorized Service Center 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 platinum 4-wire Din 43760 type, therefore, the resistance
should read 0.2 to 2.0 ohms between pins 1 and 2 on the probe con-
nector and 0.2 to 2.0 ohms between pins 3 and 4. The resistance
should read from 100 to 300 ohms between pins 1 and 4 depending
on the temperature. If the probe is defective, contact an Authorized
Service Center for assistance.
If the problem is not the probe, erroneous data in memory may be the
cause. Re-initialize the memory as discussed in the problem "The dis-
play flashes "cutout" and an incorrect process temperature" above. If
the problem remains, the cause may be a defective electronic compo-
nent, contact an Authorized Service Center for assistance.
The controller operates normally except when con-trolling at a speci-
fied set-point. At this set-point, the temperature does not agree with
that measured by the user's reference thermometer to within the spec-
ified accuracy. This problem may be caused by an actual difference in
temperature between the points where the control probe and ther-
mometer 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 ac-
cording to the certification sheet. If not, reprogram 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 tem-
perature'.
•
Check that the control probe has not been struck, bent,
or damaged. If the cause of the problem remains un-
known, contact an Authorized Service Center for assis-
tance.