Redundant Power Supply Module GE Fanuc IC670ALG620 ANALOG IN RTD Isolated Input Module
 
 
 
 
Description:
Current drawn from BIU power supply: 190 mA maximum
Digital Resolution: 15 bits plus sign
Operating temperature range: 0 to 55 Degrees C ambient
RTD types: 10, 25, 100, and 1000 ohm platinum; 10 and 100 ohm copper; 100, 50, and 120 ohm nickel; 604 ohms and 1000 ohms nickel/iron.
Resistance ranges: 0 to 500 ohms / 0 to 3000 ohms
Accuracy, at 25 C: RTD: +/-0.15% of reading, +/-0.3 to 0.5 degree Celsius, depending on type
Temperature sensitivity (0 to 60C): +/-0.004% of reading, +/-1.5V per C referred to input
Maximum lead resistance: 5 ohms per lead
Type of Device: RTD Input Module
Number of Channels: Four 3-wire and/or 4-wire RTDs
Scan time: 60 Hz: approximately 210 milliseconds per point, 50 Hz: approximately 230 milliseconds per point.
Fault detection: Open RTD, input short, underrange, overrange, and high/low alarm
Normal mode rejection: 60dB, at 50/60 Hz, 100% span
Common mode rejection: 120 dB at 50/60Hz, 100 ohm imbalance
Common mode voltage: 250 Vrms (350 VDC or peak AC)
Normal mode voltage: 100% overrange DC or peak AC operational 28 VDC or peak AC maximum
Isolation - User input to logic, user input to frame ground: 1500 VAC for 1 minute, 250 VAC continuous
Channel to Channel: 250 VAC continuous

The RTD Input Module accepts four inputs from three-wire or four-wire RTDs and converts the input level to a digital value. Input spans support a variety of RTD types, as listed in the Module Specifications section.

The analogital converter reads the voltage generated by each of the four inputs. The A/D converter converts the differential measurement into a binary value (15 bits plus sign), which is read by the block’s microprocessor. The microprocessor sets the gain required in the analogital converter for each individual input. The gain is based on the RTD type that has been configured for that input.

The microprocessor selects the input by means of a solid state, optically-coupled multiplexer.Three measurements are made for each input: Excitation current, RTD resistance including field wire drop, and field wire drop. From these three measurements, the module calculates the RTD resistance. A DC/DC converter circuit isolates the field side from the logic circuits.