1756-IRT8I ControlLogix Analog input module

The Allen-Bradley 1756-IRT8I module is a high resolution analog I/O module. In particular, it is an eight (8) point isolated temperature detection module compatible with RTD, thermocouple and millivolt signals. This module is part of the ControlLogix system and requires 36-pin RTB or removable terminal board (RTB). Compatible RTBS are 1756-TBCH or 1756-TBS6H. It has two CJC sensors for thermocouples. The CJC sensor has an accuracy of +/- 0.3 degrees Celsius, and the module’s channel sampling rate is determined only by the RPI value, as the 1756-IRT8I does not provide RTS parameters. In addition, channels configured for thermocouple input perform lead resistance self-calibration when module power is cycled. The 1756-IRT8I module features include multiple module input ranges, notch filters, underrange/overrange detection, digital filters, process alarm, rate alarm, sensor offset, 10 ohm copper offset, line break detection, temperature unit, sensor type, thermocouple line length compensation, synchronous sampling, and cold junction compensation.

The 1756-IRT8I has a variety of input ranges, namely 1 to 500 ohms, 2 to 1000 ohms, 4 to 2000 ohms, 8 to 4000 ohms, and -100 to 100 millivolts. It supports 24-bit resolutions ranging from 0 to 510 ohms at 0.06 milliohms per count, 0 to 1020 ohms at 0.12 milliohms per count, 0 to 2,040 ohms at 0.25 milliohms per count, 0 to 4080 ohms at 0.50 milliohms per count, and -101 to 101 millivolts at 0.01 microvolts per count. Supported RTD sensors include 100, 200, 500, 1000 ohms of platinum, alpha=385, 100, 200, 500, 1000 ohms of platinum, alpha=3916, 120 ohms of nickel, alpha= 672, 100, 120, 200, 500 ohms of nickel, alpha=618, and 10 ohms of copper, alpha=427. The RTD excitation current of the module is 600 microamps. The thermocouple types of this module are B, C, D, E, J, K, N, R, S, T and TXK/XK (L). ITS thermocouple is linearized to ITS-90. For thermocouple input and three-wire RTD input, the open-circuit detection time of the module is 2 seconds, and for four-wire RTD input, the open-circuit detection time is 5 seconds. Note that when the wire is disconnected from both the INx/RTD C and INx/RTD D terminals on the same channel, an open circuit (x representing the channel number) is not detected. The module has noise suppression function. In normal mode, it’s 75 dB at 60 Hertz. In common mode, 125 dB for 60 Hz 1000 ohm difference, 120 dB for 50 Hz 1000 ohm difference, and 160 dB for 600 volts 100 ohm difference.