The Allen-Bradley 1771-NB4T PLC-5 High-Resolution Analog Combination Module is an Intelligent I/O module located in a slot in the 1771 Chassis and it has 2 thermocouple/mV inputs, and 2 isolated 4-20mA outputs. It has selectable ±105mV thermocouple input ranges of Types B, E, J, R, S, and T with varying input temperature ranges and an input resolution of 3.3µV per bit at 15 sign bits. The 1771-NB4T has a display resolution of 0.01mV / 0.1°C and its input uses a Celsius/Fahrenheit ( ^oC/^oF) temperature gauge with an input impedance greater than 10 megaohms. It has a Cold Junction Compensation (CJC) of 0-70°C (at ±0.25°C) and it offers a (PTS-68) standard thermocouple linearization. The 1771-NB4T offers an upscale type, open-circuit detection, with less than 10nA maximum thermocouple leakage current, and it takes approximately 10s to detect an open input. It offers 140V AC (RMS) overvoltage protection and it has a normal mode rejection of 50dB/60dB with a common mode rejection of 150dB.

The 1771-NB4T’s input offset drift is ±0.50µV/°C, with a gain drift of ±35ppm/°C, and an input bandwidth of 9Hz. The module has an input update time of 125ms and with an input accuracy of 0.05% at 25 ^oC, and it has an input calibration of 0.000/100.000mV. The 1771-NB4T has 2 sourcing 4-20mA outputs with an output range of 0-25mA, and an output resolution of 3.2µA/bit at 13 bits unipolar. It has an output impedance greater than 1 megaohms and offers an output overvoltage protection of 140V AC (continuous). The 1771-NB4T has an output offset drift of ±1.0µA/0C, with a gain drift of ±50 ppm/ ^oC, and it has a module maximum update time of 25ms. The output has a maximum settling time of 500µs and requires 0.5mA / 22.0mA field calibration at least once a year. The 1771-NB4T has a working temperature range of 32-140 ^oF at 5-95% non-condensing relative humidity, and the whole module is keyed through pins 26 and 28 and pins 32 and 34.