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Series 830/840/860 Instruction Manual Chapter 3 Operation
IM-83/84/86-H 3-3
Motor-Operated Rotary Valve Controllers
When the transducer is installed and the system has undergone a
complete leak check:
1. Make sure the valve set point is zero before applying power.
2. Apply power. Allow thirty minutes of warm-up time. (When
power is first applied, the output signal from the transducer
remains fixed at a much higher than normal level until the sen-
sor warms up to its normal operating temperature range.)
3. Turn on the gas supply. Verify that no flow exists. Perform an
initial zero output check (only required for first-time start ups).
Set flow to zero. Connect a digital multimeter to V+out
(4-20 mA out) and COM terminals.
4. Check the reading. If it is not within ±10 mV (±0.10 mA) of
zero, adjust the zero potentiometer to zero the transducer. (The
zero pot is located behind the upper metal button on the side of
the transducer or behind the swing-out plastic door.)
5. Adjust the controller set point to the desired flow rate.
All motor-operated rotary valves seek a “deadband” where the
flow is identical to the set point within specified tolerances. Keep
this in mind when checking the instrument’s performance. For in-
stance, a 100 scfm flow controller may have a set point of 2.500
volts (50 scfm) and a flow indication of 2.550 volts (51 scfm). This
controller is working correctly, since the difference between the
flow and the set point is within 1 scfm, which is the specified accu-
racy of ±1% of full scale (0.01 x 100 scfm = 1 scfm). The width of
the deadband varies with the valve size and range of each control-
ler.
During operation, the motor runs only when it needs to. If the pres-
sure differential across the valve is insufficient to obtain set point,
the valve will open fully and the motor will cease to run. Con-
versely, if the set point is zero, the valve will close, and the motor
will cease to run. In either case, there will be no control action.
Check for adequate pressure differential and that set point command
voltage is present at the motor operator connector.