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Technical Reference
A.1
Principles of Operation
MFA 4p
Milltronics MFA 4p is a highly sensitive, single setpoint motion sensor alarm unit, used with
MSP and XPP probes. The probe detects an increase or decrease in the speed of rotating,
reciprocating, or conveying equipment and sends the information to the MFA 4p. The
MFA 4p works with a pre-amplifier which can be internal to the motion sensing probe, or
remote from the motion sensing probe. Pulses generated from the probe are continually
compared to the adjustable setpoint. If the pulse rate is lower than the setpoint, the alarm
relays operating in a faiI-safe mode will de-energize, indicating failure. The relays will not
energize until the pulse rate increases above the setpoint.
Probe
The Milltronics probes work on the principle of Faraday's Laws of Electromagnetic Induction.
When a ferromagnetic object enters the probe's permanent magnetic field, it distorts the flux
causing it to cut the coil windings and generate a voltage. This voltage is proportional to the
strength of the magnet and the number of wire turns in the coil (constant in the Milltronics
probes) and the speed at which the ferrous target passes through the flux. The generated
voltage is also inversely proportional to the square of the distance between the target and
the probe.
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Operating Instructions, 12/2020, A5E33988839-AC
A
Milltronics MFA 4p
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