GE GFK-0787B user manual Voted Analog Inputs, Number of Input Sensors per Voted Channel

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Analog Inputs

Like discrete blocks, analog blocks can be used in the input subsystem as members of GMR input groups of 1 to 3 blocks, or as non-voted blocks. Also like discrete blocks, individual circuits of analog blocks in multiple-block GMR input groups can be used as non-voted analog inputs.

Analog blocks in GMR input groups are not autotested by the GMR software.

All of the available types of analog blocks can be used, including the Thermocouple and RTD blocks. See the Genius I/O Discrete and Analog Blocks User's Manual for information about the various analog Genius blocks.

The application program can reference all analog inputs directly, whether they are located in the non-voted analog inputs area or not.

Voted Analog Inputs

For voted analog inputs, analog blocks must be set up as 2-block or 3-block input groups. The input values are in engineering units.

For a 3-block group, the GMR software compares the three corresponding inputs for each channel and selects the intermediate value. This value is made available to the application program. The application program can also access the original input values.

	Field Input Data		PLC Selects the	Single Input Provided
			Intermediate Value	to Application Logic
Input A		152

Input B

150

150

Input C

110

For example, in the illustration above, inputs A, B, and C might represent the first channel on each block in a three-block group. The PLC would place the selected input value into the first voted input word for that group.

Number of Input Sensors per Voted Channel

For each voted input channel in a 3-block group, either single or triple input sensors that are compatible with the input drive requirements of the Genius blocks can be used.

Current-loop (4-20mA) devices must be converted to voltage when a single sensor is used.

Analog Voting Adaptation

If a failure (discrepancy fault, or Genius fault) occurs, the GMR software rejects the faulty data. Depending on the configuration of the input group, input voting may go from three inputs to two inputs to one input, or from three inputs to two inputs to the configured default value.

GFK-0787B Chapter 2 Input Subsystem 2-9