Micromod MOD: 30ML Functions Data Base Reference - Manual (Page 71)

MOD 30ML Functions
BUILT-IN ANALOG INPUT BLOCK
2.7 BUILT-IN ANALOG INPUT BLOCK (AIN)
The built-in analog input block is used to gather signals from the built-in analog input circuit
and then calculate an appropriate electrical input value. The block is also the data repository
for the characteristics and origin of the input values. Connected analog input function blocks
use the input values along with the characteristic data to provide a usable signal to process.
The input function blocks can provide input filtering, action, normalization, linearization, and
scaling.
The AIN block can be configured to accept any one of the following input signal types:
• Volts
• Current
• Millivolts
• Thermocouple
• Thermocouple with Cold Junction Compensation (TC + CJC)
• Resistance
• RTD
A functional bock diagram of an AIN block is shown in Figure 2-24. The display that is used
to configure the block is shown in Figure 2-25.
2.7.1 Built-In Analog Input Block Operation
One AIN block services one input to the built-in circuit and as many other input function
blocks as required can be connected. All input values are buffered in one of five possible
state tables. Process input and output routines use these tables to pass data between the
built-in analog input blocks which get data every 100 milliseconds and the input function
blocks which run at the configured scan group interval. The input function block connected to
the AIN block latches the data according to the parameters found in the input function block’s
configuration.
Built-in analog input blocks can generate diagnostic errors based upon the following possible
conditions:
• Input circuit communications error
• Input circuit status error
During a warm or cold start condition, a pre-run read of the input circuit value is performed to
initialize the field result, conditioning and I/O task buffer values. If no I/O communications
error is encountered these values are forward initialized and their qualities are marked
GOOD, otherwise the previous values are held and their qualities marked BAD. If the block
mode is MANUAL, the pre-run read value is loaded into the field result only; the result
remains at its previous value and its quality is marked GOOD.
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