Max Machinery 286-300 SERIES TRANSMITTERS - Manual (Page 10)

The phase balancing routine that occurs for all types of meters requires 16 revolutions of the meter to
reach completion. The ‘CAL’ LED changes color (red to green or green to red) 4 times per revolution,
or 64 blinks for the entire calibration. The angular position determination (phasing) requires 8
revolutions, so the ‘CAL’ LED will blink an additional 32 times after the 64 phase balancing blinks
when calibration is performed on a piston meter. If the flow is stopped partway through a calibration,
the blinking will stop and the calibration will not reach completion since it requires a fixed number of
meter revolutions. In such a case, a new calibration should be done at a steady flow rate.
When to Calibrate
Calibration should be performed under the following conditions:
1. The Model 286 Tachometer is mated to a flow meter to which it has not been previously
calibrated.
2. If the circuit board of the Model 286 is changed.
3. If the connector between the pickup coils and the circuit board is reversed.
4. If it is suspected that the output signal contains more frequency modulation than it should have.
(i.e.: Pulse widths vary by more than 15%, and variations are not random, but cyclical at 4 times
per revolution)
Calibration Procedure
1. Ensure that S4-1 is set correctly (210 for piston meters, 220/240 for gear or helix meters).
2. Set up a steady flow rate through the meter that results in a meter rpm between 20 and 500, ideally
somewhere around 100 rpm. The position indication LED’s in the center of the circuit board can aid in
rpm determination (i.e.: at 100 rpm, each light will blink 10 times in 6 seconds).
3. Rotate S3 to the ‘0’ position to enable calibration.
4. Press the ‘CAL’ button, S5. If the ‘SLOW’ LED (D8) comes on, wait 10 seconds for it to go off,
increase the flow rate and try pressing the ‘CAL’ button again.
5. Wait for the ‘CAL’ LED (D9) to stop blinking and turn back off. While the calibration is active, the
position indication LED’s in the center of the board will pause. As soon as the calibration is complete,
they will resume activity.
6. The calibration is now complete. Return S3 to the appropriate setting to get the desired number of
output pulses per revolution.
Calibration
286-300-350 © 2002, Max Machinery, Inc. (10)
Discontinued