GE GFK-0787B user manual Analog Discrepancy Thresholds and Limits

6

Threshold Discrepancy: Specify by what percent an individual input for the channel may deviate from the voted input value. During operation, if any of the corresponding physical inputs deviates from the voted input value by more than this amount (in either direction), it will generate a fault that must be cleared by the application program.

For example, if the physical inputs for a channel were 91, 100, and 111 degrees, the voted input value would be 100 degrees. If the Discrepancy Threshold for the channel had been configured as 10%, the input reporting 111 degrees would be outside the acceptable range.

Limit Discrepancy: Similarly, specify by what percent an individual input for the channel may deviate from the full scale deflection of the channel (represented by the entries maximum and minimum value). During operation, if any of the corresponding physical inputs deviates by more than this amount (in either direction) from the voted input value, it will generate a fault that must be cleared by the application program.

For example, if the physical inputs for a channel were 9, 10, and 15, and the full scale deflection were configured at 200, with a limit discrepancy of 10%, the voted input would be 10 and all three inputs would be within the discrepancy limit (of 20), and no fault would be reported.

Analog Discrepancy Thresholds and Limits

Threshold Discrepancy

% of Reading

Discrepancy

Value

Threshold Discrepancy

% of Reading

Negative	Positive
	%AI
	Voted
	Input

Limit Discrepancy

% of FSD

NOTE: Both a Threshold Discrepancy and a Limit Discrepancy must exist for a input channel before an Analog Input Discrepancy is logged in the fault table.

Bus Connects: a triplex group connects to all three busses, so no entry is needed for Bus Connects. For a duplex or simplex group, specify the bus connections as explained below.

For a duplex group, configure the two busses the group is connected to: A (from the PLC using serial bus address 31) and B (from the PLC using serial bus address 30), or B and C (the PLC using serial bus address 29) or A and C.

For a simplex group, configure the bus the group is connected to: A (from the PLC using serial bus address 31), B (from the PLC using serial bus address 30), or C (from the PLC using serial bus address 29).

6-36	GeniustModular Redundancy Flexible Triple Modular Redundant (TMR) System	GFK-0787B
	User's Manual ± March 1995