ADT7140 I2C Temperature Sensor


The ADT7140 uses a bit more power and is a little larger than the TMP102, but it has the advantage of being able to measure much lower temperatures. The TMP102 is only good to -40 C, while the ADT7140 is spec'd for -50 C but it will actually read much lower. There are other sensors that can handle low temperature but my personal choice is to use Analog Devices components when possible.

Here's what happens when you drop a chunk of dry ice on the ADT7140. It measures down to -70 deg C no problem, and recovers to normal room temperature. Dry ice changes state from solid to gas at about -78 degrees C, but since the chuck of ice is only on top of the IC, some heat gets in from the bottom so it won't get any colder.

One use of this sensor would be measuring air temperature for high altitude balloons. The standard atmosphere is -56 C at 20k m but can get colder. Eventually I'll build a mbed based logger and send up a weather balloon with a camera - quite a few people are now doing this successfully and reaching at least 30k m. It's not really space but it's getting close.

If you want to experiment with the device, you can order it and a Surfboard (9081CA-ND) from Digikey; its size makes it fairly easy to solder. I don't see prebuilt boards from Sparkfun or other sources.

I've published a minimal library.

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