Flow meter troubleshooting

The following is essentially a reprint of the troubleshooting section in the flow totalizer manual. If you do not find what you need here, please contact us. We would like to make this section as useful as possible.

Equipment Check

The resistance and voltage checks require a high input impedance multi-meter. We recommend the inexpensive digital electronic type such as the Fluke 73.

  1. Magnetic Pick-up: Check the resistance of the pick-up. The pickup is good if the resistance is about 1,000 ohms. A bad pick-up will either be shorted (have no resistance) or read in the 1 million ohm range. Check the connector or pins for corrosion. Even a small amount of corrosion can cause intermittent operation.
  2. Rotor: Check that the rotor is turning when the product is flowing by measuring the AC voltage across the pick-up pins. The voltage reading should be at least 30 mv AC, and can be 30 volts AC or higher. Be careful not to short the pins together or to ground with product flowing, since this could damage the pick-up.
  3. Cable: Check for kinks, breaks, or other damage.
  4. Flow Totalizer: Check the power connection. Check the fuse by disconnecting power and opening the unit (note: As the fuse is soldered in and indicates possible damage, the unit must be sent to D2 for fuse replacement.) Observe precautions to avoid contaminating the unit when the cover is removed.

Trouble Shooting

 Please contact us if you are having problems that are not solvable with this table

Symptom

Possible causes

Suggested action

No display

  • no power

  • fuse blown

Check power source and power cable.

The fuse must be replaced at factory as a blown fuse may also indicate other damage.

Display is dim

  • component failure (may be caused by direct sun on the LCD display

 

Factory overhaul (Note: The older P750 board has a voltage offset potentiometer that could possibly correct this in the field)

Counting is erratic

  • poor ground connection

  • flow rate may be fluctuating
  • turbine may be jammed
  • turbine bearings may be worn

Check ground on power cord and sensor cable, and check for corrosion in cables and connectors

Check pump and line pressure.  The flow rate should be at least 40 gallons per minute for the 2" turbine, 60gpm for the 3" turbine.

Check the rotor (see below)

Factory rebuild of turbine.  A turbine can be rebuilt for about half the cost of a new one.

Working, but not counting

  • TFM rotor not turning

  • magnetic pickup defective or shorted

Check the rotor (see below)

Check sensor (see below)

To check the rotor:

While product is flowing, the AC voltage across the pickup pins should be above 30mV.  Be careful not to short across the pins with product flowing as this could damage the sensor.  If the voltage is low or erratic, there may be something resisting the flow of material across the turbine.  This could be due to salting out of product or worn bearings in the turbine.  If performance does not improve with cleaning, the turbine may be rebuilt.

 

To check the coil:

The coil itself should be free of corrosion and have a resistance of about 1000W.  A bad coil will have a resistance near zero or in the Megaohm range.  Replace the magnetic pickup if there is corrosion or out of spec resistance values and retest the totalizer.

 

If the coil is good, set the meter to measure product 8, ‘Test,’ (K-factor = 2) and pass a knife blade across the magnetic pickup.  Counts should register on the meter.  If they do not, check the connections – magnetic pickup to cable and cable to meter (in the later case you will need to open the meter.  Unplug it from the mains first).  Note: K-factor should be 36 for P752 boards.

 

 

 

 

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