ENTB non-isolated thermocouple layer

The ENTB provides non-isolated thermocouple inputs in two banks (A and B) of 16 channels. The ENTB supports the four (4) most common thermocouple types: J, K, T and E. The user-specified thermocouple type for each channel is independent of the other channels. The 16 channels of each bank share a common cold junction resulting in high channel-to-channel accuracy, which is particularly valuable when measuring thermal gradients.

Each channel uses a notched filter processor that generates about seven samples per second. Since these channels are not isolated from each other, they can only be used in applications where the individual thermocouples are electrically isolated from each other. A cold junction box is required for each bank and is connected to the ENTB with the cables provided using the connectors labeled “A01-A16” or “B01-B16” located on the front panel. Each thermocouple is connected to the miniature barrier strip type paired inputs in the junction box.

The ENTB non-isolated thermocouple layer (1-ENTB-2) measures temperatures on 32 channels of non-isolated thermocouple signal conditioning through two 37-pin high density D-sub connectors of 16 channels each. The ENTB is compatible with the four most common thermocouple calibration types: K, J, T and E. Each channel is independently software-selectable between these calibration types. Since each bank of 16 channels share a common cold junction, the ENTB has excellent channel-to-channel accuracy. This is particularly useful when measuring thermal gradients. The ENTB requires two ECJTB Cold Junction Thermocouple Boxes (sold separately) for thermocouple termination.

This diagram shows the two 37-pin D-Sub connectors on an ENTB layer.

NOTE
Thermocouple leads should not exceed 30 meters in length from connector to tip.

The ENTB uses the industry standard software compensation algorithm to generate the temperature data samples. The ENTB first measures the cold-junction compensation (CJC) temperature and converts it to the equivalent microvolt value using a high-resolution lookup table. The ENTB then subtracts the CJC equivalent microvolt value from the thermocouple’s output microvolt value. The temperature is found using another high-resolution lookup table. The lookups are based on the ITS-90 Thermocouple Direct and Inverse Polynomials.


Application Note on Measuring Differential Temperatures

To measure differential temperatures using the ENTB layer, select two or more adjacent channels on the same bank. Use matched thermocouples for optimum differential accuracy.

Due to instrumentation noise, it is recommended that the maximum sample rate (e.g., 5 Hz for the 100 KHz MSR option) and a Smoothing Filter computed channel be used for each input channel. Using a five- or seven-tap Smoothing Filter typically reduces the instrumentation noise to below 0.2° C peak to peak (for all thermocouple types). Using more taps can further reduce the noise.

To generate the differential temperature, use a simple Signal Calculator computed channel. Use a Down Sampler computed channel to achieve the desired data storage rate.


Wiring diagram

The ENTB requires two ECJTB cold junction thermocouple boxes for thermocouple termination.

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