The Xiaomi Plant Monitor, a.k.a. Huahuacaocao Plant Monitor, is a Bluetooth connected data logger that keeps track of soil moisture, fertility, light, and temperature. It is useful for monitoring the soil condition in your potted plants at home. I picked up few of these and tested them over the last two weeks.
The device comes in a nice package resembling that of an apple product. The instruction is clear and has a QR code linking to app download page. It comes with battery pre-loaded, just pull off the plastic tab from the battery compartment, and it's ready for use.
I think this is pretty straight forward. The hardest part might have been prying open the case in order to access the battery compartment. I had to use a flat screw driver to get it open.
The monitor simply goes into the soil, the black fork-shaped probe need to be almost fully inserted into the soil for the moisture reading to be accurate. The probe surface needs to come in firm contact with soil for proper measurement.
I am using "Flow Care" Version 2.5.3 running on iOS 11.2.5. The app is fairly simple to use. It shows you the live data as well as sync saved data from the devices to your account. It charts the soil moisture, fertility, light, and temperature data by day, week, or month, which is useful to see long term trends. The app comes with a database of hundreds of plants with their soil requirements pre-programmed, so you can simply look up your plant, and let the app tell you if any of the parameters are acceptable or out of bound.
The probe is estimating the soil moisture by measuring capacitance between the two legs. Therefore having the two legs fully inserted into the soil, as well as having firm contact between soil and the probe is important for having accurate reading.
The probe estimates the soil fertility by measuring conductance between the two shinny metal dots on the probe. The more dissolved mineral (such as Potassium and Calcium ions) there is in the moisture in the soil, the more conductive they should be. Just keep in mind that conductivity is all it is using, and in no way represents a comprehensive fertility of the soil (which would be incredibly difficult to quantify without more complicated tests).
I've found that the measurements seem to be consistent. They may not be accurate especially in loosely packed soil, but seems to give a good relative reference which can indicate change or deviation from norm.
After running 4 of these monitors on 4 different plants for two weeks, I have found the biggest issue is with Bluetooth connectivity. Sometimes the devices would fail to connect or sync data.
When this happens, the only way to get them back, is by removing the battery from the monitor and then put it back in. Sometimes it takes very long to connect to the probe, clearing the cache from the app helps.
The good news is that even when you are unable to connect to the probes, they are still working and logging the data, so you are not losing any data. After resetting them by removing the battery, you will be able to connect to them again and sync all the data. This is why I almost prefer to think of them as data loggers rather than monitors. I suspect that the Bluetooth connectivity issue is a firmware bug.
Another drawback is the fact that these devices would not request to connect to your phone on their own, therefore you wouldn't be getting any notifications from the app. If you were hoping that these devices would remind you to water your flowers, you may be disappointed. This is just another reason that they really are just data loggers with the ability to sync data over Bluetooth.
The Xiaomi Plant Monitor does what it is advertised to do. The measurements appear consistent and should provide some guidance on taking care of your plants. However the Bluetooth connectivity issue plagues its usefulness. More features to be desired on the app too, such as providing notifications or user programmable alert shresholds. I would not recommend this device unless these areas have been improved, at least not until the Bluetooth connectivity issue is fixed.