1771-NBVC

The Allen-Bradley 1771-NBVC is an intelligent I/O module belonging to the 1771-N series. It has 6 channels which support both voltage and current inputs rated at ±5V (±20mA) and 2 current output channels rated at 0-25 mA. The maximum current drawn from the chassis backplane by the 1771-NBVC is 1.7A and it dissipates 8.5 W while in operation mode.

The 1771-NBVC’s input channels support a ±5.5V (±22mA, with a resistor) range with an input resolution of 168µV/bit (0.7µA/bit) (at 15 bits with a sign bit) and the impedance at the input is greater than 10megaohm. 140V AC RMS (continuous) input overvoltage protection is also provided. The 1771-NBVC module requires a maximum of 5s for open input detection. 50 dB/60 dB is the minimum normal mode rejections while the common mode rejection that is provided is typically 150 dB. The values for offset drift are ±20µV/°C (±85nA/°C, with a resistor) and the values for the gain drift are ±35 ppm/°C (±55ppm/°C, with a resistor) whereas the input channels’ bandwidth range is 9 Hz. The 1771-NBVC’s update time is a maximum of 25 ms per module. The calibration values are 0.0000V/5.0000V and the under-range and over-range thresholds are 0.8V DC (3.2mA) and 5.2V DC (20.8mA) respectively.

The 1771-NBVC’s output channels support a 0-25mA range and a resolution of 3.2µA/bit (at 13 bits unipolar) with an output impedance greater than 1megaohm. 20mA is the maximum drive capability for a 0-1kiloohm circuit, and 25mA is the drive capability for a 0-700ohm circuit. The offset drift value is ±1.0µA/°C and the gain drift value is ±50ppm/°C. Allen-Bradley recommends using the 1771-NBVC with the 1771-RTP4 device, which is a termination panel suitable for applications other than those involving thermocouples. The 1771-NBVC’s working temperature range is between 32 and 140°F at a 5 to 95% relative humidity range, non-condensing.