INTRODUCTION
I-E96-301B
2 - 1
SECTION 2 - DESCRIPTION AND OPERATION
INTRODUCTION
This section explains the inputs, control logic, communication
and connections for the Universal Analog Input Slave Module
(IMASI03). The analog slave interfaces 16 analog inputs to the
Multi-Function Processor (MFP). The information in this sec-
tion will answer most questions about how the IMASI03 works.
Read this section and
slave.
FUNCTIONAL OPERATION
The IMASI03 is an intelligent INFI 90 slave module with an
on-board microcontroller and memory. It interfaces to INFI 90
master modules over the slave expander bus. An on-board
microcontroller allows the IMASI03 to do the input channel
processing. This allows the master module to do other tasks.
Input processing tasks include error compensation, adjust-
ments and conversion to engineering units.
BLOCK DIAGRAM
Each input channel has an isolation amplifier used to isolate,
filter and amplify the analog input signals. This isolation
amplifier also contains references used for on-line calibration.
Each channel accepts voltage and resistance inputs. Resis-
tance measurements are made by digitizing the voltage drop
created across the input resistance source. A precision con-
stant current source supplies the current used to measure the
input.
Each channel provides under-range, over-range and open
input detection. On-board circuitry detects either open field
wires or a disconnected termination device cable. Open input
detection is provided for all input types and can detect any
combination of open input wires.
The IMASI03 has a single, software programmable, high reso-
lution analog-to-digital converter that digitizes channel signals
and references. A very low drift system voltage reference allows
continuous software calibration of the A/D Converter. A sys-
tem reference also provides the source for the cold junction
input that allows the slave to compensate for cold junction
errors introduced when connecting thermocouple signals.
The IMASI03 communicates with the MFP through a shared
memory interface connected to the slave expander bus. The
IMASI03 constantly updates the shared memory device (Dual
