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2.6.4 - Internal Temperature Sensor [U6 Datasheet]

The U6 has an internal temperature sensor.  The sensor is physically located near the AIN3 screw-terminal.  It is labeled U17 on the PCB, and can be seen through the gap between the AIN3 terminal and adjacent VS terminal.

The U6 enclosure typically makes a 1 °C difference in the temperature at the internal sensor.  With the enclosure on the temperature at the sensor is typically 3 °C higher than ambient, while with the enclosure off the temperature at the sensor is typically 2 °C higher than ambient.  The calibration constants have an offset of -3 °C, so returned calibrated readings are nominally the same as ambient with the enclosure installed, and 1 °C below ambient with the PCB in free air.

The sensor has a specified accuracy of ±2.1 °C across the entire device operating range of -40 to +85 °C.  Allowing for a slight difference between the sensor temperature and the temperature of the screw-terminals, expect the returned value plus 3 °C to reflect the temperature of the built-in screw-terminals with an accuracy of ±2.5 °C.

With the UD driver, the internal temperature sensor is read by acquiring analog input channel 14 and returns °K.

The internal temperature sensor does not work in stream mode.  It takes too long to settle, thus if you stream it you will typically get totally wrong readings.

Note on thermocouples

If thermocouples are connected to the CB37, you want to know the temperature of the screw-terminals on the CB37.  The CB37 is typically at the same temperature as ambient air, so use the direct value from a read of AIN14.  Better yet, add a sensor such as the LM34CAZ to an unused analog input on the CB37 to measure the actual temperature of the CB37.

The built-in screw-terminals AIN0-AIN3 on the U6 are typically 3 °C above ambient with the enclosure installed, so when the internal temperature sensor is used for CJC for thermocouples connected to the built-in screw-terminals, it is recommended to add 3 °C to its value as you want the actual temperature of the screw-terminals, not necessarily ambient temperature.

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