Calibration; Underspeed - Siemens milltronics MFA 4P Instruction Manual

Although two pulses within range are required to energize the relays, as long as the
frequency of the incoming pulses exceeds the setpoint frequency (or is less than that of
the setpoint in the case of overspeed detection), the MFA 4p keeps the alarm relays
energized. The reference generator is frequency adjustable by the pulses per minute
(ppm) switch and potentiometer.
The alarm relays will de-energize after two time constants of the setpoint when the
frequency of the incoming pulses falls below that of the setpoint (or exceeds that of the
setpoint in the case of overspeed detection). The relay status is indicated by Relay LED 2,
which is illuminated when the relays are energized (normal).
The MFA 4p has a 0 to 60 second time delay feature, allowing the monitored device to
accelerate to normal running speed before monitoring begins.
This feature is activated when power is applied to the MFA 4p in parallel with the motor
starter contact coil. The time delay circuit simulates normal operating conditions for the
amount of time as set by the Start Delay potentiometer, keeping the alarm relays
energized. If the monitored device does not reach normal speed before the set time
period, the relays will de-energize giving an alarm condition. This feature is not applicable
in the overspeed detection mode.

Calibration

The probe and pre-amplifier require no calibration.
Connect the probe, pre-amp, and MFA 4p as shown in the Interconnection diagrams on
pages 8 and 9. Connect the MFA 4p to power as shown in the Power Connection diagram
on page 10, and if applicable, as shown for Automatic Start Delay on page 11.
To help the calibration procedure, short N.O. contacts of relays to prevent
Note:
motor shut-down (terminals 1 to 2 and/or 4 to 5). This allows the system to run
uninterrupted until an operating setpoint is established.
MFA 4p (Refer to MFA 4p Circuit Board layout on page 7.)
1. Operate monitored equipment at its normal operating speed.
2. Confirm that Probe LED 1 is pulsing at a regular frequency.
3. Set Start Delay fully counter-clockwise (CCW) to 0 seconds.

Underspeed

1. Set switch SW3 to Underspeed.
2. Set pulses per minute (ppm) switch SW2 to X 100 position.
3. Turn ppm potentiometer fully clockwise (CW) to 30.
4. Determine incoming pulse rate by slowly turning ppm potentiometer CCW until relay
LED 2 goes on. As the MFA 4p requires 2 pulses within range before energizing
relays, low ppm applications (e.g. 2 ppm) may require stepping of potentiometer at
appropriate time intervals.
Page 14 MFA 4p – INSTRUCTION MANUAL 7ML19985FM01