Allen Bradley 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 sensing module compatible with RTD, Thermocouple and millivolt signals. The module is part of the ControlLogix system and requires the 36-pin RTB or Removable Terminal Block (RTB).

Compatible RTB are 1756-TBCH or the 1756-TBS6H. It has 2 CJC sensors for thermocouple use. The CJC sensor accuracy is +/- 0.3 degrees Celsius, The channel sampling rate of the module is only determined by the RPI value because the 1756-IRT8I does not offer the RTS parameter. Also, channels configured for thermocouple inputs perform a lead resistance self-calibration when the module power is cycled. Features of the 1756-IRT8I module include multiple module input ranges, a notch filter, under-range/over-range detection, a digital filter, process alarms, a rate alarm, a sensor offset, a 10-ohm copper offset, wire-off detection, temperature units, sensor types, thermocouple wire length compensation, synchronized sampling, and cold junction compensation.

The 1756-IRT8I has multiple input ranges available, 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 resolution with ranges of 0 to 510 Ohms with 0.06 milliohms per count, 0 to 1020 Ohms with 0.12 milliohms per count, 0 to 2040 Ohms with 0.25 milliohms per count, 0 to 4080 Ohms with 0.50 milliohms per count, and -101 to 101 millivolts with 0.01 microvolts per count. RTD sensors that are supported include 100, 200, 500, 1000 Ohm platinum, alpha=385, 100, 200, 500, 1000 Ohms platinum, alpha=3916, 120 Ohms nickel, alpha 672, 100, 120, 200, 500 Ohm nickel, alpha=618, and 10 Ohm copper, alpha=427. The RTD excitation current of the module is 600 microamps. The thermocouple types for this module are B, C, D, E, J, K, N, R, S, T, and TXK/XK (L). Its thermocouple linearization is ITS-90. The module has open circuit detection times of 2 seconds for a thermocouple input and 3-wire RTD input and of 5 seconds for a 4-wire RTD input. It should be noted that there is no open circuit detection when wires are simultaneously disconnected from the INx/RTD C and INx/RTD D terminals on the same channel (with x representing the channel number). Noise rejections are available for the module. At normal mode, it is 75 dB at 60 Hertz. During common mode, it is 125 dB at 60 Hertz 1000 Ohms differential, 120 dB at 50 Hertz 1000 Ohms differential, and 160 dB at 600 Volts 100 Ohms differential.

The Allen Bradley 1756-IRT8I is a ControlLogix analog input module with Eight (8) channels configurable for Resistance Temperature Detector (RTD), Thermocouple and millivolt input.

This module features high resolution analog to digital conversion via Sigma-Delta method. The converted data is saved to IEEE 32-bit floating point. The converted data are ideally accessed by Human Machine Interface (HMI), Supervisory Control and Data Acquisition (SCADA) and Distributed Control Systems (DCS). Other than computer-based systems, the signal data may be used for calculations, and Process Variables (PV) for controllers such as Proportional + Integral + Derivative (PID).

This module is capable of Open Circuit Detection with detection time of 2 Seconds for Thermocouple input and 3-Wire RTD and 5 Seconds for 4-Wire RTD.

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Specification Sheet .pdf