CHAPTER 3 - OPERATION FLUID COMPONENTS INTL
3. Operation
Caution:
The control circuit contains electrostatic discharge (ESD) sensitive devices. Use standard ESD
precautions when handling the control circuit. See Chapter 2, Installation for ESD details.
Factory Calibrations
The RF83 Flow Switch is delivered in its standard factory set point form unless a custom factory calibration was
specified. The standard factory setting is mid-range between no flow and full flow. See Figures 3-1 and 3-2.
If the order included custom factory calibrations and alarm set points, keep all settings unchanged. The instrument is
ready for service without changes.
Field Calibrations for Flow Applications
If the factory calibrations were not ordered then follow one of the procedures below based on the particular
instrument purchased. If precise measurement is desired, FCI recommends that a FM71 Monitor/Calibrator be used.
Then the precise measurement of the signal voltage versus flow rate can be calculated for the alarm set points.
Alarm Set Point Adjustments By Observation or By Measurement
Alarm set points can be adjusted by observation or by precision measurements. The following procedure is
adjustment by observation. If adjustment by measurement is desired, obtain an FCI FM71 Calibrator/monitor and
follow the instructions found in the FM71 manual. For the highest accuracy,balancing the control circuit and creating
a calibration curve should be performed. These subjects are addressed later in this chapter.
Alarm A Set Point Procedure
1. Flow the pipeline at the desired flow direction and rate of flow.
2. Apply power to the instrument and allow 15 minutes for the sensing elements to become active and stabilize.
3. Locate the potentiometer (R5) and the red LED on the control circuit. (See Figure 3-3 or 3-4.)
4. Choose A or B.
A. Detecting No Flow or Decreasing Flow Rate
If the LED is off, turn the potentiometer clockwise until the LED turns on. If the LED is on, turn the potentiometer
counterclockwise until the LED turns off, then turn the potentiometer clockwise until the LED just turns on. With the
LED on, turn the potentiometer slowly counterclockwise until the LED just turns off. Turn the potentiometer onehalf turn past the point at which the LED just turns off. Be aware that the potentiometer may have up to one quarter
turn of hysteresis. If the mark is overshot, the procedure should be repeated. See Figures 3-1and 3-2 for
potentiometer position and curve results.
B. Detecting Maximum Flow or Increasing Flow Rate
If the LED is on, turn the potentiometer counterclockwise until the LED turns off. If the LED is off, turn the
potentiometer clockwise until the LED turns on, then turn the potentiometer counter clockwise until the LED just
turns off. With the LED off, turn the potentiometer slowly, clockwise until the LED just turns on. Turn the
potentiometer one-half turn past the point at which the LED just turns on. Be aware that the potentiometer may have
up to one quarter turn of hysteresis. If the mark is overshot, the procedure should be repeated. See Figures 3-1 and
3-2 for potentiometer position and curve results.
Doc. No. 003147 Rev. B 3 - 1
Model RF83 Flow Switch
FLUID COMPONENTS INTL CHAPTER 3 - OPERATION
Figure 3-1. Setting Forward and Reverse Alarm Switch Points
Figure 3-2. Control Circuit Outline Drawing
Model RF83 Flow Switch 3 - 2 Doc. No. 003147 Rev. B
CHAPTER 3 - OPERATION FLUID COMPONENTS INTL
Alarm B Set Point Procedure
1. Flow the pipeline at the desired reverse rate of flow.
2. Apply power to the instrument and allow 15 minutes for the sensing element to become active and stabilize.
3. Locate the potentiometer (R20) and the green LED on the control circuit. See Figure 3-1 for the potentiometer
location.
4. Choose A or B.
A. Detecting Reverse No Flow or Reverse Decreasing Flow Rate
If the LED is off, turn the potentiometer clockwise until the LED turns on. If the LED is on, turn the potentiometer
counterclockwise until the LED turns off, then turn the potentiometer clockwise until the LED just turns on. With
the LED on, turn the potentiometer slowly counterclockwise until the LED just turns off. Turn the potentiometer
one-half turn past the point at which the LED just turns off. Be aware that the potentiometer may have up to one
quarter turn of hysteresis. If the mark is overshot, the procedure should be repeated. See Figures 3-1 and 3-2 for
potentiometer position and curve results.
B. Detecting Maximum Flow or Increasing Flow Rate
If the LED is on, turn the potentiometer counterclockwise until the LED turns off. If the LED is off, turn the
potentiometer clockwise until the LED turns on, then turn the potentiometer counter clockwise until the LED just
turns off. With the LED off, turn the potentiometer slowly, clockwise until the LED just turns on. Turn the
potentiometer one-half turn past the point at which the LED just turns on. Be aware that the potentiometer may have
up to one quarter turn of hysteresis. If the mark is overshot, the procedure should be repeated. See Figure 3-1 and
3-2 for potentiometer position and curve results.
BALANCING
The balance number is the resistance difference between the two RTDs (A and B) when the heaters are disconnected.
The balance number is recorded on the edge of the control circuit on a white block with the lettering "BALANCE
NO." written above it.
Generally it is not necessary to obtain the balance number for an application which requires only a switch. However,
for detecting flow direction a precise balance is required since either a small positive or negative voltage output is
used as the indicator.
Balancing is usefull to obtain a calibration curve for the instrument, it is essential to balance the control cirucit. The
accuracy of the calibration is dependent on an accurate balance number. Balancing is also needed if the instrument
switch points are going to be adjusted by numerical values.
Balance the instrument when the balance number can not be found or if the accuracy seems to be incorrect.
Delta R, the difference between the sensor A and sensor B RTDs is used for balancing. Balancing the voltage
(Ohm's law V=I x R) to zero is accomplished by making the difference between the two RTDs zero.
Determining The Balance Number:
Setup Required
FCI FM71D Calibrator
Sensor immersed in process media at zero flow
Power source to power up the switch circuit board
1. Verify the sensor mounting in the process line is correct. Insure there is a no-flow condition in the process line.
2. Verify the correct wiring configuration and then disconnect the heater circuits.
3. Connect the FM71D calibrator (terminal 7,8 and 9 which is labeled on the FM71D calibrator) to the control
circuit, apply power to the instrument.
Doc. No. 003147 Rev. B 3 - 3
Model RF83 Flow Switch
FLUID COMPONENTS INTL CHAPTER 3 - OPERATION
5. Dial the bridge balance dial to the balance number on the control circuit.
6. Allow the FM71D display to stabilize (at least 10 minutes) at a certain millivolt (the voltage may vary
+/-1 mV). If the reading is zero, balance is OK and FM71 may be removed and heaters reconnected. If the
reading is not zero, a new balance number must be generated by the following steps:
7. Dial the bridge balance dial to produce a zero on the FM 71D calibrator readout. The number should be stable
over a 10 minute period (it may vary +/- 1 mv).
8. Read the new balance number of the bridge balance dial and record it on the face of control circuit.
Note:
The balance number is not permanently fixed into the instrument. When the calibrator is used for that
same instrument, then re-enter the balance number recorded earlier. It is necessary to enter the balance
number or verify the balance of the circuit board to the calibrator each time the FM 71D is used.
Creating a Calibration Curve Using the Millivolt Output Option
The zero adjust procedure should be performed before the instrument calibration curve is measured. Millivolt points
in between the actual measurement points may be used for indicating the corresponding flow.
1. Apply power to the instrument and establish a constant flow rate in the pipe for the first data point to be taken.
Let the instrument stabilize for 10 minutes.
2. With a high impedance DMM measure the voltage from terminal pin 8 (+) to 11 (-). Record the flow rate versus
the meter readout.
3. Repeat steps 1 and 2 at different flow rates. Record enough flow points to be able to make a millivolt versus
flow curve.
Creating a Calibration Curve Using an FM71 Calibrator
1. Apply power to the instrument and establish a constant flow rate in the pipe for the first data point to be taken.
Let the instrument stabilize for 10 minutes.
2. Attach an FM71 meter to the control circuit. Dial in the balance number found near the edge of the control
circuit. The read out /calib. switch should be in the readout position. Record the flow rate versus the meter
readout.
3. Repeat steps 1 and 2 at different flow rates. Record enough flow points to be able to make a millivolt versus
flow curve.
To set a switch point using numerical values, use the instructions that come in the FM71 manual.
Model RF83 Flow Switch 3 - 4 Doc. No. 003147 Rev. B
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