Honeywell HC900 - AI Function Block

Function Blocks
AI Function Block
42 HC900 Hybrid Control Designer Function Block Reference Guide Revision 11
2/07
AI Function Block
Description
The AI label stands for Analog Input.
This block is part of the I/O Blocks category.
Function
Reads value of an Analog Input from a specified real I/O address. Convert analog input value to
corresponding output (OUT) in engineering units based on the necessary scaling and conversions
performed.
LINEAR - Converts analog input value to corresponding output in units based on a linear 0 % to 100 %
scale and specified high and low range values +/-10% over range.
OUT = Scale x Input value + Bias
where:
High range value - Low range value
100
Scale =
Input value = Analog Value in percent
T/C or RTD - Converts analog input value in engineering units using the range of Input Type. +/-1% over
range.
ATTENTION
The failsafe detection on this input block configured for 4-20mA range is:
Low Detection: 2.4mA
High Detection: 21.6mA
Outside of the range the flag (Input Fail) is ON. There is no detection from 0 to 4 mA, but the
block continues to provide data that can be compared via an Alarm Block, for example.
Input
Analog value from specified real I/O address.
DIS = disable the AI channel
Output
OUT = Analog Input value in engineering units.
WARN = Warning Input Indication - Sensor failure possibility. If AI input wiring or sensor exceeds
100 ohms of resistance, the WARNing pin will energize.
FAIL = Digital status of channel
Digital Low (0) = OK
Digital High (1) = Open sensor or failed input channel.