National Instruments NI-9214 C Series Temperature Input Module

The high-density thermocouple input module NI-9214 (Part Number: 781510-01) from National Instruments is intended for systems that need more channels than they currently have. For offset error compensation, it has one internal autozero channel in addition to sixteen thermocouple channels. Along with a configuration intended to reduce heat gradients and improve overall accuracy, the module incorporates Cold-Junction Compensation (CJC) sensors in the terminal block.

The NI-9214 ensures accurate measurements of voltage and temperature because of its 24-bit ADC resolution and Delta-Sigma type ADC. It operates in scanned sampling mode, with a voltage measurement range of ±78.125 mV. It provides support for the J, K, T, E, N, B, R, and S thermocouple types as defined by NIST. This module provides strong protection against common-mode voltage fluctuations, with a minimum of ±1.2 V for channel-to-COM and ±250 V for COM-to-earth ground. The device exhibits remarkable common-mode rejection rates in high-resolution mode, measuring 100 dB between the channel and the COM, and 170 dB between the COM and the earth ground.

With varying bandwidths and noise rejection properties, there are two operating modes: high-resolution and high-speed. Providing outstanding noise rejection of 65 dB, the high-resolution mode runs at 14.4 Hz bandwidth. When it comes to noise rejection at 50 and 60 Hz, the high-speed mode provides a somewhat reduced bandwidth of 80 Hz. The NI-9214 ensures the safety of connected devices by incorporating an overvoltage protection of ±30 V between any two inputs. It has a 20 MΩ differential input impedance, low input noise levels, and, depending on the mode, RMS values that range from 220 nVrms to 2.8 μVrms.

With sensitivity ranging from 0.01 °C to 0.48 °C depending on the kind of thermocouple and operating mode, temperature measurement accuracy is remarkable. Accurate cold-junction compensation is also offered throughout a variety of temperatures. The NI-9214 module can be used with screw-terminal wiring that has a required torque and gauge range. It has IP40 ingress protection and can operate in temperatures between -40 and 70 degrees Celsius, demonstrating its resilience to challenging environmental conditions.