ABB CK-MAG 10D1477 Instruction Manual page 46

10D1477 MAGNETIC FLOWMETER INSTRUCTION MANUAL
6.3 Static Test
If improper operation of the magnetic flowmeter is suspected, the following resistance measurements
can be made to establish whether an electrical malfunction has occurred. A standard multimeter is
suitable for making the resistance checks. These measurements can be made at the CMF/BUFFER
board in the meter electronics base.
Equipment that operates from ac line voltage constitutes a potential
electric shock hazard to the user. Make certain that the system power is
disconnected before making the following ohmmeter checks.
6.3.1 Magnet Coil Check
There are two magnet coils in the meter that are connected in a series arrangement. The respective
coil leads are brought up to lugs "M1 and CT1" and "CT and MR" on the CMF/BUFFER board in the
meter electronics base. Figures 5-1 and 5-2 show the actual connection method.
Before making resistance measurements, verify that the system power service has been de-ener-
gized. Remove the electronics housing cover to obtain access to the CMF/BUFFER board.
1) Set the ohmmeter to its lowest range; e.g., R x 1.
2) Connect the ohmmeter test leads to terminal lugs M1 and CT1 on the CMF/BUFF-
ER board. The value displayed should correspond to 1/2 of the value ( ± 20%) indi-
cated in Table 6-1.
3) Connect the ohmmeter test leads to terminal lugs CT and MR. The value displayed
should correspond to that obtained in Step 2 and as indicated in Table 6-1 within
± 20%.
If proper coil resistance is measured, it can be assumed that the magnet coils are functional. If the
measurement indicates that either or both coils are "open" (infinite resistance), the magnetic flowme-
ter must be replaced.
4) Carefully remove the four coil wires from the terminal lugs on the CMF/BUFFER pc
board. Identify each wire to enable its proper reconnection.
5) Set the Ohmmeter to its highest range (R x 10,000) and measure from wire lead M1
or MR to the meter body (case ground). The resistance reading should be infinite. If
this measurement is less than 100 K ohms, the meter is defective and must be
replaced.
When all measurements appear normal, the coil wires can be reconnected and the meter can be
returned to service. Replace the meter housing cover.
WARNING
6-3