Rain Bird
Flow Sensors
Manual
10
Troubleshooting
1)
Using a voltmeter on the 0-20 VDC scale, connect the voltmeter across the sensor wires which are
connected to the sensor input on the barrier strip. The voltage reading should be 8 VDC +/
– 0.5 V with no
flow in the pipe. If the reading is in range, go to step 2. If not, go to step 3.
2)
With the sensor installed in the pipe and flow through the pipe, connect the volt meter across the sensor
wires at the sensor input of the barrier strip. The voltage should fall between 4 VDC and 8 VDC. The
higher the flow rate, the lower the DC voltage level should drop. It should not drop below 4 VDC as your
meter averages the DC level of the square wave signal generated by the sensor.
If this is correct, the flow sensor should be operational, and the flow monitor should display a flow rate or
the transmitter output should change with a change in flow at the sensor. The signal generated by the
sensor is a square wave with 5 msec pulses up to 100 Hz (at which time the pulses narrow to a 50% duty
cycle), the use of an oscilloscope on the 5 msec time base, 2 VDC/division would indicate that the sensor
is operating properly.
3)
If the voltage at the sensor input is less than 7 VDC in a No Flow situation or less than 3 VDC in a flow
situation, disconnect the sensor from the barrier strip and measure the voltage at the sensor input
terminals of the barrier strip again. It should be between 8 VDC and 12 VDC. If the voltage is between 8-
12 VDC, the sensor is bad. If the voltage at the sensor input is still below 7 VDC or 3 VDC, the problem
may be with the monitor.
4)
If you suspect that the sensor is bad, you can test the monitor circuitry by connecting a piece of wire to
one of the sensor input terminals and tap the other side of the wire to the other sensor input terminal.
Shorting across the sensor input terminals ON and OFF repeatedly allows the display to respond by trying
to calculate a flow rate for the frequency of your shorting action. If the display does not show a change
from 0.00, it indicates a problem with the monitor.
5)
If the flow sensor wiring is shorted or grounded the blue light on the module may blink continuously.
Disconnect the flow sensor wire from the module in the controller. Remove and reinstall the module and
the flow rate should return to zero. If secondary surge protection was installed remove it. Check sensor
wiring for: 1) damaged insulation; 2) wire nuts must be direct burial type Rain Bird DBRY20 or 3M
DBR/Y-6; and 3) sensor should be connected on dedicated PE-39 cable with no other signals in the
cable. Fix the wiring and test the system.
