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Instruction Manual
Form 5300
July 2005
increasing input signal. Tighten the cam locknut,
leaving a gap of approximately 0.80 mm (0.031
inches) between the cam and roller. Tighten the cam
nut to 3.8 to 9.1 nSm (30 to 75 lbfSin).
6. Reconnect the output tubing to the actuator.
Zero and Span Adjustments
See figure 19.
1. To start this procedure, if necessary, unscrew the
four captive cover screws (key 8) and remove the
cover assembly (key 7).
2. Apply supply pressure.
3. Provide a way to check the input signal. Apply the
minimum input signal. For example:
D For a Type 3710 pneumatic positioner, if the
input signal range is 0.2 to 1.0 bar (3 to 15 psig),
apply 0.2 bar (3 psig).
D For a Type 3720 electro-pneumatic positioner,
if the input signal range is 4 to 20 mA, apply 4 mA to
the Type 3722 converter.
W5916/IL
Figure 18. Loosening the Cam Locknut
3710 and 3720 Positioners
The zero adjustment locknut and zero
adjustment knob are identical parts,
key 35.
4. Loosen the zero adjustment locknut (key 35) and
turn the zero adjustment knob (key 35) until the
actuator moves the valve to the proper position. This
valve position must correspond to the minimum input
signal.
Tighten the zero adjustment locknut before
proceeding to step 5.
5. Slowly increase the input signal until the input
reaches the maximum input signal. Observe the
actuator travel and valve position as the input
increases. Determine the actuator/valve position at
the maximum input signal.
6. After observing the actuator/valve travel at
maximum input signal, return the input signal to the
minimum input signal before turning the span
adjustment knob.
Note
21
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