Manual mode enables the user to apply a value directly to the loop controller output.

Select this mode from the Control Expert Debugging screens.

Switching to Manual mode simply requires sending a single command. Once this command is acknowledged, Manual mode is indicated by the STS_AUTO_MANU status bit.

Control of the loop or loop controller command may then be initiated. If the command is a numeric value, it is subject to high and low thresholds, as well as speed limitation. The output is processed each time the task cycles.

Manual control is always done on the OUT_MAN variable. This variable ranges from 0 to 100. However, since OUT_MAN is not directly linked to the actual position of the actuator, it's essential to still be able to open and close the actuator, even if OUT_MAN reaches its upper or lower threshold. To do so, it is possible to assign OUT_MAN a value beyond its normal range: OUT_MAN will be limited, yet the change affecting the calculated command will be taken into account by the Servo function.

For example: OUT_MAN = 100.0; actuator is open at 50%. To attain a 70% opening, enter OUT_MAN = 120.0. OUT_MAN then takes on the limited value of 100.00.

In Automatic mode, the command value is calculated by the loop controller based on the setpoint and PV values.

Switching to Automatic mode is done from the Control Expert screens. You may also switch modes by sending a single command. Once the command is acknowledged, the system uses the STS_AUTO_MANU status bit to confirm the switch to Automatic mode. The output is processed at each cycle of the sampling.