I have a few of them and was also curious about this.
I placed them as close to my Nest thermostat as I could and the readings were +/- 1% on humidity and +/- 0.5% on temp.
Good to know, and thanks for sharing.
I have seen other post reporting around +10% compared to other devices.
I have another devices, cheap one not so trustable, that differs 8-10% with SNZB-02…so i was little bit unsure what to believe.
The discrepance seems to be just humidity, temperature is quite similar to other devices.
I have four SONOFF SNZB-02 it’s absolute garbage VERY inaccurate humidity
temperatures are accurate BUT look at the humidity!
It currently shows 80% to 95% humidity, but I tested with 3 other hygrometers and the real humidity is 63% in grow tent 1 and 72% in grow tent 2
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Hi guys, I am a bit confused. I read conflicting comments concerning the accuracy of the humidity sensor. Can someone share their experience.
Any alternative is also welkom. Accuracy (and size) is very important in my case, I will be using it for my (cigar)humidor.
I have 3 of them, no others and my first/only experience with these kind of devices (had lights and switches)
Compared the temp with a thermometer and had to adjust all 3 of them with the same value (-1,3°C).
I have no other means to compare the humidity values but they seem to be correct.
Hi guys
I wanted to share my experience.
Fluctuation : It seems the sensor is fluctuating a bit. In a steady environment (cigar humidor and ziplock bag) the fluctuations were within a range of 2% which seems reasonable to me.
Offset: I read comments about testing the accuracy by comparing it to another sensor. In my opinion, this is very strange (how would you know the other sensor is accurate?).
What you should do instead is the “salt test”. Create a conditioned environment where you know (thanks to physics) that the humidity will be a certain value. (75% in this case). You do the test and there you have it: the offset. About 4% in my case.
Note that the other sensor is off by 2% in the other direction.
Because I could not find if the offset is to be adjusted in the Sonoff SNZB-02 sensor, I did it within HA by adding the following code to the configuration.yaml:
This allowed me to have an accurate reading of the humidity with the appropriate notification (avoiding to ruin my cigars)…
Have fun!
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Just wanted to share my personal experience with the Sonoff SNZB-02. I purchased two of them. On one of the two devices, the setup button was depressed into the case. I popped the case open (there are no screws) to discover that the tiny microswitch was poorly soldered to the board. It actually fell off into my hand when I tried to press the button with my finger.
I was able to configure both devices. For the one without a setup switch, I used a flat blade screwdriver to bridge the contacts for five seconds. Both devices reported temperature, humidity and 100% battery levels. I walked away thinking that I was done.
A few days later I logged in hoping to see a graph of temperatures and humidity. I was disappointed to find that the devices (both) stopped reporting and were now “unavailable”.
For the one device that had a setup button, I did a reconfigure to get it up and running again. It was reporting data one again. In my logbook I have a “Identifybutton” event, but no further logs from the device. It reported the temperature and humidity once.
The next morning I expected to see a graph of temperatures and humidities. Once again, nothing. Only the one reading when I reconfigured the device. Perhaps I’m missing something, but my experience so far can only be summed up as disappointing.
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I bought 4 of them, mostly because I like the bigger battery.
One had the same problem as @paulcarlin is reporting - the setup button was depressed into the case :-/ , very poor quality and not something I would expect for a button (that gets broken when you press it omg)…
And the other 3? Over the course of 3 days, only two are somewhat reliably report the temperature. One of them just drops off, when I “repair” it by holding the pairing button, it reports the temperature like once and then drops off. This is next to 3 additional routers (extending the signal) that are connected just fine, so it’s not out of range or something. Changed the battery, same behavior… The sensor, however, reports more often than just once in an hour.
50% survival rate is not great 
, seems like a hit and miss.
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@kotrfa Glad to hear it’s not just me. I ended up purchasing Aquara sensors and have had no issues with them.
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Same here, I’M very disappointed. I used Aquara temp sensor for years without problems.
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I bought two SNZB-02 and added them to my Home Assistant on the RPi 4.
Pairing was easy to ZHA.
One did not really want to update the Humidity, temperature was OK.
Cured with doing a Reconfigure of the device.
Since then the temperature and humidity are reported. Not often, e.g. it needs 0.2 change for the temperature to report. So it saves battery that way I think. After two days the batteries are still at 100%.
So far so good. Accuracy is 0.2 degrees, humidity is 2%.
I have also two Aqara Temperature and Humidity Sensors. One is just as good/bad as the Sonoff devices, the other is eating batteries in a day, so garbage now.
The spikes were created by breathing on the sensors, to force a report.
Home Assistant 2023.5.2
Supervisor 2023.04.1
Operating System 10.1
Frontend 20230503.3 - latest
Zigbee Home Automation
Been running three SNZB-02 for over a year on MQTT. Did salt test and compared temperature with other thermometers - I my case it is all in spec. Battery fluctuates after re-pair, but other than that these are still close to 100%. One out of three sometimes disappear from network, but it’s only happened few times in a year.
People experiencing connection issues - ZigBee is very weak especially for battery powered devices. Something like moving sensor 5cm in other direction might cause massive drop in link quality. Things like using electrical devices can also cause network degradation. I just keep an eye on situation using chart
I bought 2 of them - both drop off the network within a day. Using ZHA and not interested in moving everything over to MQTT.
I also have negative experience with Sonoff SNZB-02. Bought 2 of them, to work together with SONOFF Zigbee 3.0 USB Dongle Plus + ZHA. Both were paired without any issues, humidity is updated every ~30s (or every minute, not sure here) reliably, but temperature was updated once right after pairing, and then not updated at all. I tried multiple times to remove battery and re-pair, but the behavior is still the same 
I can’t blame the setup, because Aqara sensors works perfectly in the same time.
Seems like the SNZB-02 in general has issues based on the thread and such, I currently have the SNZB-02P that has been working without issue… so far, paired through ZHA on the skyconnect.
The thing is: are you questioning the device because of a zigbee issue that comes from your mesh which results in connection loss/having to repair or the accuracy of the sensor.
If you are running a zigbee network, you know that it’s not that obvious to have a reliable mesh.
In my HA, I am running Zigbee2MQTT version 1.40.2 with a EmberZNet coordinator on a flashed Sonoff ZBDongle-E.
My Sonoff SNZB-02D H-T sensor is not consistently updating Temp and humidity consistently 3/4 times an hour as seems to be the expected default. There are long, 3-5 hour periods when I receive no updates at all.
The Sonoff HT sensor is located about 6m from the Zigbee coordinator and it displays a fairly good link quality of 118.
Anyone else having the same problem?
I am using an automation based on THIS to manually poll all SNZB-02 sensors every 5 minutes. Works flawlessly.
trigger:
- trigger: time_pattern
minutes: /5
action:
- action: homeassistant.update_entity
target:
entity_id: >
{{ integration_entities('sonoff')
| select('search', 'temperature|humidity') | list }}
I have the very same behavior, but its the humidity that gets updated only once after pairing. Did you find a solution?
Try a new battery regardless of what the battery % the sensor tells you.
Mine said 72% battery, and still have iirc 3v when I use a multimeter to test the battery. So out of desperation I went ahead and used a fresh battery.
Et voala. It worked, at least for me.
Oh and btw, I have since changed the sensor readings reporting frequency & threshold.