Electrode Check; Flowmeter Board - ABB MINI-MAG 10D1475 Instruction Manual

10D1475 MINI-MAG MAGNETIC FLOWMETER INSTRUCTION BULLETIN

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.
Before proceeding, verify that system power has been de-energized. To perform this test, the meter
must be removed from the pipeline and the meter liner "wiped" dry. When the meter liner has been
thoroughly dried, proceed as follows:
1) If integral Signal Converter supplied, begin with step a, below. If a remotely mounted
Signal Converter is supplied, begin with step b.
a) Remove meter housing cover from electronics compartment. Loosen the four
mounting screws that secure the integral Signal Converter to the meter base. Dis-
connect plugs P1 and P3; set the Converter aside. Proceed to step 2.
b) Remove field wiring connected to electrode leads "1" and "2". Proceed to step 2).
Electrode wiring is shown in Figure 4-1 and 4-2, as applicable.
2) Place Ohmmeter on highest available range (for example, R x 10,000).
3) Connect the Ohmmeter "minus" lead to the meter ground stud and the "plus" lead to
electrode line 1. This reading should be infinite. If any resistance can be measured, the meter
is defective and must be replaced.
4) Check the other electrode by connecting the Ohmmeter "plus" lead to line 2. This reading
must also be infinite. If any resistance can be measured, the meter is defective and must be
replaced.
5) If measurement of both electrodes indicates an infinite resistance reading, the meter may
then be returned to on-stream operation after wiring has been restored. Re-install the
integrally mounted Signal Converter, if applicable, and replace housing cover.
If the Signal Converter has been removed from the housing, use care when
reconnecting the Converter interface cable to ensure that plug P1 is in
proper alignment with the pins of receptacle J1. (J1 is located on the base
board in either the Flowmeter or the remote Converter housing, as the case
may be.) If these connectors do not mate correctly, the Signal Converter
will be inoperable and could be damaged when power is applied.
5.3.3 Flowmeter Board (Model 10D1475J)
The Flowmeter board is located in the base of the electronics housing. This pc board includes the
constant meter factor/size network. The constant meter factor/size network functions to standardize
the particular flowmeter; i.e., provide a constant meter capacity that will be the same for all meters of
the same size.
The constant meter factor/size network is factory set by precise calibration prior to shipment. This
calibration procedure (used to establish the exact setting for the particular constant meter factor/size
network) compensates for variations resulting from manufacturing tolerances. Hence, the value of
constant meter factor/size network on each primary board is unique and may be applicable only for
the particular flowmeter for which it was supplied.
5-4
NOTE
MAINTENANCE