Problem
Causes and Solutions
The display flashes
“Cutout” alternately with
an incorrect process
temperature
Low battery
. A problem could exist with the memory back-up battery. If the bat-
tery voltage is insufficient to maintain the memory, data may become scrambled
causing problems. A nearby large static discharge may also affect data in mem-
ory. Access the battery by removing the back panel covering the display
electronics.
Corrupt controller memory.
If the problem reoccurs after the battery is re-
placed, initialize the memory by performing a Factory Reset Sequence (de-
scribed in a previous solution).
The controller displays
the wrong temperature
and the bath continually
heats or cools regardless
of the set-point value
Bad control probe.
The bath control probe may be disconnected, burned out,
or shorted. Check first that the probe is connected properly to the socket in the
rear of the bath labeled “PROBE”.
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. The resistance should read 0.2
to 2.0 ohms between pins 1 and 2 on the probe connector and 0.2 to 2.0 ohms
between pins 3 and 4. The resistance should read from 100 to 300 ohms be-
tween pins 1 and 4 depending on its current temperature.
Corrupt controller memory.
Initialize the memory by performing a Factory Re-
set Sequence (described in a previous solution).
The controller controls or
attempts to control at an
inaccurate temperature
If the controller appears to operate normally except that the bath’s temperature
does not agree with the temperature measured by the user’s reference ther-
mometer to within the specified accuracy, consider the following:
Erroneous parameters.
Check that the calibration parameters are all correct
according to the Report of Calibration. If not, reprogram the constants. If the
controller does not keep the correct parameters, the memory backup battery
may be weak causing errors in data. See “Low Battery” in a previous solution.
Poor uniformity.
There may be an actual difference between the bath’s control
probe and the reference thermometer due to excess gradients in the bath.
Check that the bath has an adequate amount of fluid in the tank and that the
stirrer is operating properly. Also check that the reference thermometer and
control probe are both fully inserted into the bath to minimize temperature gradi-
ent errors.
Bad control probe.
Check that the control probe has not been struck, bent, or
damaged. Refer to the previous solution for how to check the probe’s
resistance.
6020 Series Calibration Bath
User’s Guide
70
