Spectrum Controls 1734sc-IF4U - Manual (Page 11)

Chapter 1: Module Overview 1-5
User’s Manual Pub. 0300266-01 Rev. A
1.6.1 Module Power-up
At power-up, the module performs a check of its internal circuits, memory, and basic
functions. If no faults are found during power-up diagnostics, the module status LED is
turned on.
After power-up checks are complete, the module waits for valid channel configuration
data. If an invalid configuration is detected, the module will generate a PLC fault. Once
a channel is properly configured and enabled, it continuously converts the input data to a
value within the range selected for that channel.
1.6.2 Module Operation
The 1734sc-IF4U module provides four independent analog input channels. Each
channel includes four selectable filter settings and can be configured for voltage,
thermocouple, current, resistance or RTD input types.
The 1734sc-IF4U module utilizes a 20-bit Sigma-Delta ADC (Analog to Digital
Converter) to achieve 18-bit resolution. Inputs to the ADC are first multiplexed through
analog switches then buffered by a precision, low offset and drift, programmable gain
amplifier. The ADC also provides the programmable current source used in resistive
measurements.
The 1734sc-IF4U plug-in module communicates over its isolated CAN Bus interface
through the module backplane. The 1734 network adapter then communicates to the PLC
controller. See the block diagram below.
+24VDC
+3.3VDC ±2%
‐15VDC ±3VDC
GND
Isolated
CAN Bus
CAN
Bus
and
+5VDC
ADC
SPI Interface
Voltage / Current (4‐chs)
RTD / Resistance (2/4‐chs)
Thermocouple (3‐chs)
GND
Analog_1
Analog_0
I
s
o
l
a
t
i
o
n
Point Bus
LEDs
Processor
Isolation
Barrier
Controls and Status
Controls
Notes:
1) I/O’s are ESD protected
CJC (1‐ch)
Analog_2
Protection,
Filtering,
Analog
Switch
Matrix,
PGA
+15VDC ±3VDC
Current Srcs
PGA_Interrupt
Low
Input‐Power
Interrupt
and
System_Reset
SPI Interface
Power Supplies
And
Power Monitor
Isolation
Barrier
CLK
System
Clock
Generator