GE Baker Hughes Masoneilan SVI FF Installation And Operation Manual page 135

ATO / ATC
WARNING
The positioner must be configured as Air-to-Open, ATO, or as Air-to-Close, ATC. If the
positioner has a double acting relay, the action is defined for the output labeled ACT1, or
Output 1.
To determine if a direct acting positioner is considered ATO or ATC perform the following test:
1. Apply the actuators rated pressure to the positioner supply.
CAUTION
2. Disconnect the electrical input signal from the positioner or set it to less than 9 V.
3. Observe the position of the control valve. If it is closed the actuator is ATO. If the valve is
open it is ATC.
Valve Characteristics
The positioner must be configured to supply the correct relationship between input signal and
valve position. This is called the position characteristic. Table 29 lists characteristics for
configuring the positioner.
Use of a linear characteristic is recommended unless the process dynamics or control valve
application calls for an alternate characteristic. SVI FF offers a custom characteristic for
specialty applications. Prior to selection of custom, the parameters for the custom
characteristic must be entered using ValVue.
NOTE
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This procedure can cause the valve to move. Before proceeding be
sure the valve is isolated from the process. Keep hands clear from
moving parts.
Do not exceed actuator pressure rating on the control valve
specification sheet. Damage to the valve stem, shaft, or trim can
occur.
The characteristic configured in the positioner is applied in
addition to the plug characteristic built into the valve trim. Do not
configure a percentage characteristic if the valve has a
percentage plug.
Masoneilan SVI FF Instruction Manual
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