DESCRIPTION AND OPERATION
BLOCK DIAGRAM
I-E96-301B
2 - 3
Each input channel can be independently configured for reso-
lution through individual function code 216 blocks. The reso-
lution and approximate conversion speed are shown in
function code 216.
Microcontroller and Memory
The on-board microcontroller coordinates IMASI03 functions.
The main functions are:
•
Calibrating the A/D converter.
•
Isolation amplifier input reference switching.
•
Channel and cold junction reference switching.
•
Programming A/D resolution.
•
Reading the A/D and applying all necessary correction
factors.
•
Interfacing to switch and LED (used for diagnostic mode).
•
Background integrity checks.
•
Reads and writes of expander bus data through dual port
RAM (DPRAM).
Cold Junction Reference
The IMASI03 measures the cold junction RTDs on the slave's
termination device. This results in an accurate reading of the
ambient temperature at the field wire termination area. This
value can be used by the slave to compensate for voltages gen-
erated from the bimetal connections made by terminating the
field wires (thermocouple wires) onto the terminal blocks of the
termination device.
The block address of the cold junction reference used by ther-
mocouple inputs on the slave is contained in function code 215
specification 3.
Each slave configured for a thermocouple input requires a cold
junction reference. Each slave can only have one reference
which can be used by up to 16 thermocouple inputs. The
exception to this is when one of the inputs is used as a remote
cold junction reference.
Refer to
for more information.
