Circuit Description; Model 10D1475J; Primary Signals; Constant Meter Capacity (Cmc) Pc Assembly - ABB MINI-MAG 10D1475 Instruction Manual

10D1475 MINI-MAG MAGNETIC FLOWMETER INSTRUCTION BULLETIN

4.0 CIRCUIT DESCRIPTION

4.1 Model 10D1475J

4.1.1 Primary Signals

The Model 10D1475J flowmeter uses remote 50XM1000 Converter electronics.The Magnetic Flow-
meter body houses two signal electrodes and two flux producing magnet coils. All Flowmeter
intraconnection wiring is terminated at the CMC/ZERO PC board located in the base of the meter
housing.
The Flowmeter provides two output signals to the associated Signal Converter; one, an electrode
signal that contains the flow rate information, and two, the reference signal which is proportional to
the magnet excitation current (theoretically, this reference signal is proportional to the flux density in
the metering section). The reference voltage is derived across a precision "constant meter factor"
resistance network that is connected in series with the magnet coils. Changes in magnet drive
voltage, which cause a variation of flow signal, will simultaneously cause a proportional variation of
the reference voltage. The circuitry will provide an exact ratio and thereby provide immunity to power
supply variation. The magnet coil drive circuitry is contained in the Signal Converter.
The (gated) magnet driver operates at a frequency that permits magnetic flux in the Flowmeter to
reach a steady state level during the last 25% of each half period of magnet excitation. By using
sampling techniques, the flow (differential mode) signal is measured only during the intervals that
magnetic flux is constant:



Therefore, zero instability due to changing flux is eliminated by use of the MAG-X design concept
(sampling technique), providing a meter totally free of zero drift. A thorough discussion of Signal
Converter operation is provided in the Instruction Bulletin supplied with the particular Signal Con-
verter.

4.1.2 Constant Meter Capacity (CMC) PC Assembly

The CMC PC Assembly provides several functions. These include:
1. Establishing interconnections between the Flowmeter internal wiring and
the Signal Converter.
2. Permitting factory adjustment of meter capacity values to a fixed value for
each nominal size Flowmeter.
3. Permitting factory adjustment of Flowmeter zero.
4. Establishing proper wiring connections for remotely mounted Signal Con-
verters.
CIRCUIT DESCRIPTION

dΦ
= 0 

dt
4-1