Calibration For 4194Hb And Hc Controllers; General Calibration Instructions - Emerson Fisher 4194HA Instruction Manual

Differential pressure indicating controllers

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Instruction Manual

D200156X012

proportional band percentage from the equation below:

Proportional

+ 200

Band

Adjustment

For example:

5. If the controller is used with a control valve, return the control valve to service by slowly opening the upstream and

downstream manual control valves in the pipeline. Close the manual bypass valve, if one is used.

6. Tune the various controller actions.

D Tuning proportional action: Create a load upset by momentarily changing the set point. Check for system

cycling. If the system does not cycle, lower the proportional band setting (thus raising the gain) and disturb the

system again by changing the set point. Continue this procedure until the system cycles. At this point, double

the proportional band setting (proportional band setting X 2).

D Tuning reset action: Disturb the system. If the system does not cycle then speed up the reset by changing the

setting to a lower value (faster reset) and disturb the system again. Continue this procedure until the system

cycles. When the system cycles, multiply the reset time setting by a factor of three (reset time 3) and slow down

the reset by changing the setting to the higher value. The reset is now tuned.

D Tuning rate action: For a controller with rate (4194HC controllers), adjust the rate toward the lowest setting until

cycling occurs. When the system cycles, multiply the rate value by a factor of three (reset time X 3) and slow

down the rate by changing the setting to the higher value. The rate is now tuned.

7. Check the stability of the recommended proportional band setting by introducing a disturbance and monitoring

the process.

8. Once stable control is attained, the process indicator and set point adjustment indicator should be in line. If they are

aligned, return the set point to the desired value. If they are not, readjust the set point to the desired control point

on the process scale and proceed with step 9.

9. If the process indicator is within ±5 percent of the set point indicator, turn the link 3 adjustment (see figure 5‐3 for

location) until the process indicator aligns with the set point indicator. Turn the link 3 adjustment screw clockwise

to increase the process indication or counterclockwise to decrease it. If the process indicator is misaligned with the

set point adjustment by more than ±5 percent of the scale span, perform the calibration procedure for 4194HB and

HC controllers.