Someone using reliable OUTDOOR Humidity Sensors?

Question

I would like to understand who of you was already testing nodes with humidity sensors on and found them accurate in quality.

Definition of quality:

  • accurate measurements especially also in the area of > 80 % RH
  • battery life of at least 1 year
  • sensor is outside the node (not inside and has therefore delayed measures)

Precision

I am aware that there are numerous IoT shops and companies outside there that are offering devices. My question is really who already used some nodes - either ready made or even DIY that are running for a longer time span outside and what the experiences were.

Also, I would like to understand how you evaluated the accuracy.

What I am NOT searching for

A list of links to possible devices. I can’t effort buying all and everything. I believe in the power of this community by sharing experiences with stuff that was used in practice already.

Background

I am searching for a suitable solution for a case in the area of agriculture, mainly frost monitoring but not only.
The price per device should not exceed 80 EUR.

Already tested ones

  • DIY node with AM2305 sensor
    • temp measures seem be less accurate however acceptable and provides humidity measure without latch-up’s so far
    • battery life is an issue, did not get further than 15’000 transmits (which of course depends on the board you are using) with my DIY node - which is of course not necessarily caused by the sensor
  • DIY node with Si7021 sensor
    • same behavior as the RS 1xx (same sensor)
  • Laird RS 1xx
    • I was reporting about my parallel test in this topic
    • very good temp measures, latch-ups for humidity by 1:1 comparison with the AM2305 and an official weather station
    • lot of restarts/re-connects however battery life seems rally good
  • I would be looking to test the Dragino LHT65 next - maybe someone did already?

Looking forward to reading about your experiences. Thanks so much in advance!

You can use ,
BME280
BME680

Hi @suendermarkus, I use a number of Netvox R712 temp/humidity sensors in agriculture. I have not had them formally calibrated for accuracy but they seem to be close to correct.
This datasheet http://www.netvox.com.tw/um/r712/r712DataSheet.pdf lists the temp accuracy as +/- 1degC and the humidity accuracy at +/- 4.5%.

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Thanks. Which is the device you are using them in?

have a look at https://ruuvi.com/. They use BME280 in a waterproof housing. Possibly find some more experience reports here.

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Best sensor ever.
https://www.sensirion.com/de/umweltsensoren/feuchtesensoren/digitale-feuchtesensoren-fuer-diverse-anwendungen/

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Thanks for the link, looks really awesome. Did you eventually happen to see a node that is using that sensor? Or is more for DIY usage?

Both works great

I have only this like an DIY. https://www.sensirion.com/en/environmental-sensors/humidity-sensors/sht85-pin-type-humidity-sensor-enabling-easy-replaceability/
But heltec has one option for an HDC1080.
Also good sensor. https://heltec.org/project/htcc-ac01/
And you I know also Sensirion has a sensor to plug like heltec.

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I have been using Sensirion SHT21 and SHT25 for many years, e.g. in strawberry foil tunnels with LoRa (not LoRaWAN) together with soil moisture sensors for irrigation control. You should pay attention to the following aspects:
At high humidity usually all sensors have less accuracy, some may even fail after long term exposure to high humidity (I remember a project in the tropical rain forests where we had quite some problems)
A good radiation shield may be required which can be quite expensive (more expensive that the whole electronics). In the foill tunnels I use a simple tube which is sufficient for this application.
See for long term drift in the datasheet of the sensor you choose.
Erdbeer

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Many thanks for your valuable input @dk9uv .

One question if I may: Eg in your foil tunnel project, how did you protect the electronics?
I’ve been talking to people that studied electronics some had serious doubts DIY nodes would survive.

For my prototypes I usually put the LoRaWAN board into a IP67 case and just kept the breakout board with the sensor outside.

In long term I prefer something like on the picture below with an appropriate sensor inside:
image

@cristianhumelnicu BME280 will break down within 6 months if exposed to condensation. We concluded it’s not very suitable for outdoor use.

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@EFthings01 How do you measure humidity in a waterproof housing? :wink:

The best thing you can do is epoxy potting which I do for my soil moisture sensors and lasts for years. In the foil tunnel project I used Urethan 71 spray which worked quite well for a whole season with no degradation. Completely enclosed commercial sensors with filter are very good but quite expensive as far as I know (e.g. state of the art rotronic HygroClip). Below you will see some measurement results on frost detection (you mentioned in your inital post). In 2017 there was a severe frost event and the farmer lost 90% of the strawberries (we told him later why :-)) Don’t worry about the high daytime peaks, there was an insufficient radiation shield.

Sensor_0002_0003_0004

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If you refer to the Ruuvi, then they gave the answer in the specs:

The environmental sensor breathes through an IP67 certified water-resistant vent sticker made by GORE.

However, your question is basically showing the crux of the whole thing: the sensor will break sooner or later if you’re exposing it as-is to an outdoor environment but protection is going to impact the measures. I believe @dk9uv gave a good indication how a suitable protection could work - together with the radiation shield.

Yes I agree two things care about. Radiation shield. And yes a good sensor with an protection like the sht85 is expensive.
I have same thing to my weather station.
I am testing at the moment different things. But fact I will use the sht35 and build up my own node. I can inform you if a have finished it. But that can take a year. It is just an hobby.

Same here @MOS-FET, is a hobby for me as well. And: as most sensor work well in conditions > 25° you have just the winter period once a year for good tests unless you have a foil tunnel at home :sweat_smile:

Then try SI7021 wich have autoheat function embedded , but is not so stabile like BME280

@cristianhumelnicu Yes, but still this sensor too is specified for non-condensing situations and indoor usage.

In fact do not exist special sensors for indoor or outdoor , the difference is the enclosure that is suppose to be used for outdoor

You can use SI7021 with internal heater for humidity in conjunction with DS18B20 wich is a very stable temperature sensor or BME280 /BME680 with right outdoor enclosure like all of us