IM-P693-13 EMM Issue 2
10
CP42 Conductivity Probe
There are no available spare parts for this product.
6. Spare parts
Problems experienced during commissioning are often found to be due to incorrect wiring or setting up, so
we recommend that a thorough check is first carried out.
Checking probe condition using the probe cell constant:-
The controllers have a facility which allows the condition of the probe driver tip to be checked without
removing the probe from the boiler. This is done by calculating an approximation of the probe cell constant,
an indication of the probe condition.
A probe driver tip which is functioning correctly without excessive scaling will have a cell constant of between
0.2 and 0.6. See the 'Fault finding' Section of the Installation and Maintenance Instructions for details.
The sensor tip condition cannot be checked by the following blowdown controllers but it can be checked
by using the MS1 conductivity meter.
Checking the probe condition using the MS1:-
The condition of an installed probe can be checked by using a Spirax Sarco MS1 conductivity meter and
its extension lead.
Driver tip:
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Connect the MS1 extension lead between terminal 1 and terminal 3.
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Use the reading to calculate the driver tip cell constant as described in the MS1 instructions. A cell
constant in the region of 0.2 to 0.6 would indicate that the probe is working correctly. A high figure
indicates that the probe is scaled.
Sensor tip:
-
As for driver tip, but connect the MS1 between terminals 2 and 3.
A sensor tip cell constant of 0.2 to 0.6 is normal, but a figure up to 0.8 is satisfactory.
Pt100 resistance check:
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The power must be off for this check.
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Measure the resistance between terminal 7 and terminal 8. A conventional ohm meter may be used for
this test. Resistance should be between 100 ohms (0 °C/32 °F) and 168 ohms (180 °C/356 °F).
Terminal 3 should be earthed to the probe body.
7. Fault finding
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