Have been programming arduinos for a while now, mostly playing around with the Spakrfun inventor kit. But I’ve also been wondering the best way to measure temperature. I know there are a few sensors out there, but I want to measure temperature for my next project and it seems like it would be good to have a range of options,. I don’t mind if I have to write some code, just want a couple options.
The DHT22 works great. Already in a plastic package and measures both temperature and humidity. In addition to using that sensor, I have worked with the MCP9808 and DS7505 both for the class now and they both work just fine for temperature with accuracy up to 1/16th degree C. They don’t measure humidity.
Yep, those are good sensors/measurement methods that Brooke mentions. I would also wonder which topologies you’ve tried? Do you have a cost restrictions? What kind of temperature ranges are you trying to measure?
For example, measuring the temperature of the glass on a sunny day would be much different than the ambient temperature inside a greenhouse.
For beginners, I would recommend trying one of the i2c sensors that are cheap and readily available. The DS7505 that Brooke mentions is the one that we use on the CE Header sensor board.
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@ChrisGammell makes an excellent point about knowing your needed temperature range. I would bet the glass temperature is out of the range for all the sensors I listed. The DS7505 only handles -55°C to +125°C. The MCP9808 has a smaller range of -20°C and +100°C and the DHT22, according to Adafruit, even has the same smaller degrees range, but different min/max temperatures of -40 to 80°C.
What should I use if it’s above those ranges then? Something with IR?
I generally search DigiKey, Mouser, or your favorite parts vendor.
I was able to find an I2C part that goes up to 150C for $2.57/ea.
https://www.digikey.com/product-detail/en/maxim-integrated/MAX6633MSA-/MAX6633MSA--ND/1513501
Some very quick Googling seems to indicate that 100C/212F would be awfully darn hot in a greenhouse. It would be good if you had some way to measure the temperature simply, before working on your planned electronic device. This would help in planning for the parts you need as well as validating that your sensor is matching another instrument.
According to some reading, if your greenhouse has active ventilation, this will also greatly control the inside temperature.
I took a look for some commercial solutions to get an idea of the specs being used:
-40°C to 125°C http://www.monnit.com/Products/Wireless-Sensors/Coin-Cell/Wireless-Temperature-Sensors
-85° to 76°C http://www.sensaphone.com/products/sensaphone-sentinel-monitoring-system.php
-51° to 49°C http://www.charleysgreenhouse.com/6608-Low-Cost-Min--Max--Thermometer---N2608-.htm
If you want to go past these temperatures (though not for a greenhouse, like Brooke said), I normally recommend going towards an RTD or a thermocouple. The latter can go to very high temps. Just another type of technology to look into.
Hi All,
I just received the LT Journal of Analog Innovation, April 2017, Volume 27 Number 1.
In it, there are a couple or articles on temperature measurement, including thermocouples.
Regards,
Niels
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