National Instruments NI 9213E

The National Instruments NI 9213E is a 16-channel thermocouple input module intended for use in industrial automation applications. It has a 36-terminal detachable spring-terminal connector that makes connecting thermocouples simple. The module's 24 bit analog-to-digital converter (ADC) multiplexes and samples each channel after it has passed through a differential filter. The two common terminals (COM) on the module are internally coupled to the isolated ground reference.

It is advised to connect COM to shielded thermocouples and the shield to a common-mode voltage reference. The COM and the shield need to be linked to earth ground when utilizing floating thermocouples or thermocouples close to it. Each channel has an open thermocouple detection (OTD) circuit that detects open thermocouples by means of a current source between the TC+ and TC-terminals.

For offset error compensation, the NI 9213E also incorporates an autozero channel and cold-junction compensation (CJC). The module uses a maximum of 490 mW of power while it is in active mode and just 25 μW when it is in sleep mode. The maximum thermal dissipation in active mode is 840 mW, while in sleep mode, it is 710 mW at 85°C. This temperature measurement module provides accuracy and flexibility with 16 thermocouple channels, 1 internal autozero channel, and 1 internal CJC channel.

With a voltage measuring range of ±78.125 mV, it uses a 24-bit Delta-Sigma ADC in scanning sampling mode. The NI 9213E is compatible with J, K, T, E, N, B, R, and S thermocouple types, spanning NIST temperature ranges. The kind of thermocouple and the measurement mode chosen affect temperature measurement accuracy. The measurement sensitivity in high-resolution mode is less than 0.02 °C for types J, K, T, E, and N, and less than 0.15 °C for types B, R, and S. With type B having a sensitivity of less than 1.2 °C, the sensitivity in high-speed mode varies from <0.25 °C for types J, K, T, and E to <2.8 °C for types R and S.