Electrode Check; Full Pipe Test; Empty Pipe Test - ABB COPA-XM 3000 Series Instruction Manual

Series 10DX3000 Magnetic Flowmeter Instruction Manual
Verify that the system power service has been de-energized. Loosen and remove the four screws
that hold the Signal Converter to the base. Disconnect the connector from signal (P1) on the CMC PC
board and the power (P3) connector to the Converter (refer to Figure 3-2) and set the Converter
module aside. Measure the series resistance of the magnet coils by connecting the ohmmeter
between terminals M1 & MR. The value displayed should be between 10Ω and 80Ω.
If it is suspected that process fluid or excess moisture has entered the Primary housing, unsolder the
coil wires from the M1 and MR pads. Verify that the resistance of each coil lead (M1, MR and CT) to
the flowmeter body is greater than 20 MΩ or infinite. If the resistance value is incorrect, the coils are
defective and the meter must be returned to the factory for service.

5.3.2 Electrode Check

The electrode check is essentially a resistance measurement that can be made to establish that a
short (or high resistance leakage path) does not exist between one, or both, electrodes and the meter
body. Verify that the system power service has been de-energized.
To thoroughly test the electrodes of flowmeters with remote converters (Model 10DX3111E), meters
must be tested under both full and empty pipe conditions. If this is not possible, it may still be helpful
to perform one of the tests since useful partial information may be gained from the results of either
portion of the test.

5.3.2.1 Full Pipe Test

The wetted electrodes of all flowmeters manufactured in accordance with FM Div.1 or Div.2 require-
ments must have energy-limiting resistance placed in series with them. Depending on the model
being tested, the nominal resistance value is 100,000 ohms and will add to any resistance measured
between the wetted electrode and the fluid in contact with that electrode.
Electrode full pipe measurements should be made with the ohmmeter placed on its highest range. An
AC type ohmmeter (i. e. conductivity bridge) is preferred because DC voltage will tend to polarize the
electrode (but will nevertheless provide meaningful information). Connect the ohmmeter positive
lead first to electrode terminal "1" and then to electrode terminal "2" with the negative lead to terminal
"3" or the flowmeter body. The measured resistance should be 100,000 ohms plus the intrinsic
resistance between electrode and fluid (typically 50,000 additional ohms or less). If using a DC
ohmmeter, the resistance between the electrode and the fluid will tend to increase as the electrode
becomes polarized by a DC signal. This effect is normal. AC resistance readings will not vary once
established. Readings greater than 150,000 ohms may indicate a coated electrode. Infinite readings
indicate a broken connection in the electrode wiring path. Meters with infinite full pipe readings
should be returned to the factory for repair.

5.3.2.2 Empty Pipe Test

If possible, the pipeline should now be drained and the flowmeter should be given a few minutes to
allow the fluid to drain off the electrode to liner interface. Connection of either a DC or AC ohmmeter
between electrode terminals "1" or "2" and the meter body (terminal "3") should result in a reading
greater than 20 MΩ. Lower readings indicate either that process fluid has leaked behind the
electrode or that moisture has entered the flowmeter housing. If this is the case, the defective meter
should be returned to the factory for repair.
5-4