Analog Input Modules
TC Module IOP304
Metso Automation MAX Controls Inc. • 277596 •
5-3
to the field side of the measuring circuit. Communication between the
microcontroller and the A/D is serial at 100kHz. Optical isolators provide
the isolation between the field side and the serial logic circuits. The
microprocessor provides the input data to the DPU on demand via the bus
FPGA. The FPGA provides the I/O bus interface logic; its program is loaded
from the FLASH on power up.
Module calibration is done automatically at power up following startup
diagnostics. Calibration is repeated periodically online to compensate for
temperature effects.
When thermocouples are measured, the module monitors the TC cold
junction temperature and the input value read is compensated for the cold
junction temperature. Thermistors, installed at the terminal blocks provided
above and below the field connectors, are used to measure the TC cold
junction temperature. When remote terminations are used, these thermistors
must be removed from the module and moved to the wiring connections at
the remote terminations. The microcontroller schedules periodic
measurements of the thermistors and uses these measurements to calculate a
cold junction temperature for each channel.
Channel 1
Channel 16
FLASH
FPGA
I/O Bus
Regulator
24V
uC
DC/DC
5V - field
OPTO
optical isolation
field to logic
A/D
REF
O
PEN
TC
Field Interface
Circuits
Diagnostics
The module executes diagnostics on power up. When an error is detected on
power-up or during online operation, the front-panel green LED, labeled
Active, blinks the first digit at a slower rate and the second digit at a faster
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