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Service and maintenance
5.1
Calibration
The probe and pre-amplifier require no calibration.
Connect the probe, pre-amp, and MFA 4p as shown in the Interconnection (Page 12) chapter.
Connect the MFA 4p to power as shown in the Connection to Power (Page 16) diagram, and
if applicable, as shown for MFA 4p Wiring for Automatic Start Delay (Page 17).
Note
To help the calibration procedure, short N.O. contacts of relays to prevent motor shutdown
(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 (Page 11)
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.
5. If no response is obtained when you set the ppm potentiometer to 3 (below this stability
suffers), reset potentiometer fully CW, set switch SW2 to X 10 and then X 1 if required, and
repeat step 4.
6. When Relay LED 2 goes on, indicating the incoming pulse rate, turn potentiometer CCW
slightly past this point to obtain an operating setpoint that allows for normal fluctuations
due to load and voltage variations. For 50 % of full speed, set potentiometer (and SW2 if
required) to halfway between incoming pulse rate of normal speed and 0 ppm.
7. Set Start Delay by adjusting potentiometer so that equipment being monitored can attain
normal operating speed before LED 2 can turn off.
18
Operating Instructions, 12/2020, A5E33988839-AC
5
Milltronics MFA 4p
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