Question: What are good humidity sensor/monitors to use with gas sampling kits?

gretchengehrke asked on January 29, 2018 20:37
140 | 2 answers | #15636


Humidity can have substantial impacts on several kinds of sensors and monitors of gaseous pollutants, such as particulate matter optical sensors, hydrogen sulfide corrosion sensors, and formaldehyde chemical reaction sensors. Particulate matter sensors are often near-real-time, generating a ton of data, but the low-cost hydrogen sulfide and formaldehyde sensors we've been working on use an integrated 3-day to 30-day sample. What are good humidity sensors to use alongside these pollutant sensors to help make the pollutant sensor data more interpretable?

Some thoughts that come to mind are: - able to record data over hours, days, or weeks - able to transmit data to a storage location or store data locally - stable in a variety of temperatures - outdoor weatherproofing (or able to have housing easily made for it) - inexpensive

Does anyone know of good, inexpensive humidity sensors commercially available? Or DIY ones that are simple to construct and use?



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2 Answers

Kestrel makes a well-thought-out data logger called Kestrel Drop. The Drop D2 logs temperature and humidity apparently for six months. You can retrieve the data anytime with your phone via bluetooth (so you have to be close). Kestrel Drops are weather resistant. Their app will graph your results, but I don't know if you can get the raw data. The D2 costs $100.

D2Blue_grande.jpg

Temperature and humidity are easy to measure and easy to log with any Arduino. Good sensors for temperature and humidity cost $5.00 (BME280). So the parts to make a temperature and humidity logger cost $20 on eBay. The data will be saved to a microSD card at any interval in csv or any format you want.

A kit to make a Mini Pearl Logger with a BME280 sensor costs $31.50 at the KAPtery. Or a solder free kit plus sensor is $50.00.

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A weatherproof enclosure must keep rain away from the logger but allow some air to circulate in to read the humidity. You also have to keep direct sun off of everything.

Humidity measurements don't have much meaning without temperature information because warmer air holds more water. So you need both, and humidity is usually presented as relative humidity which incorporates the temperature information.

Chris


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