Manual

9-6

IM 21B04C50-01E

9.2.3 Limit Switch Threshold

The Limit switch thresholds apply to the Discrete Input (DI) block setpoints.

● Threshold Low

The threshold for the low limit switch that communicated by the DI block.

● Threshold High

The threshold for the high limit switch that communicated by the DI block.

9.2.4 Fault Control

● Error Band

The position deviation limit to start deviation timer of Time 1 and Time 2.

Set this value to a value that is exceeded only in abnormal performance.

● Time 1

The position deviation time limit to show the block alarm. A negative value turns off this

function. Set this value greater than the stroking time.

● Time 2

The position deviation time limit to trigger the failsafe action. Enter “-1” to disable this

function. A negative value turns off this function. Use of the Time 2 failsafe may result in

unwanted process shutdowns.

WARNING

Use the Time 2 failsafe only for a critical process that must be forced into its failsafe position

if the valve is unable to respond to its position setpoint after a reasonable time delay. Do

not set the error band to a value that is too small. If Time 2 is used, it must be longer than

the valve stroking time. A Time 2 value that is too small will result in nuisance failsafe

behavior.

9.2.5 Servo Alarms (I/P Module Operating Point Fault Control)

This function is applicable only to the device revision 4 or higher (or the device revision 2 or

higher when the software download functions are available).

● Servo Warning High

If the operating point of the I/P module is more than this value, the timer that measures the

time after the I/P module operating point error starts.

● Servo Warning Low

If the operating point of the I/P module is less than this value, the timer that measures the

time after the I/P module operating point error starts. Input a value that is the same as or

less than that for Servo Warning High.