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Panasonic Button Battery CR2477
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Expert4House – Smart Home Automation
Sonoff AirGuard TH SNZB-02M Zigbee Temperature, Humidity, and Air Pressure Sensor
€18.90
€23.90
Save €5.00Tax included
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- Five metrics in one sensor: measures temperature, humidity and atmospheric pressure, and the eWeLink app derives dew point and VPD.
- Stated accuracy: ±0.2 °C for temperature, ±2% RH for humidity and ±0.1 hPa for pressure.
- Pressure from 700 to 1100 hPa: barometric trends anticipate weather changes and let you adjust climate and ventilation in advance.
- Zigbee 3.0 over IEEE 802.15.4: low-power, low-latency network, with the sensor acting as a node without using Wi‑Fi bandwidth.
- Over 2 years of battery life: powered by a CR2477 3 V battery, no cables or power adapter required.
- Compact size 45 × 45 × 17.6 mm: 27.3 g with battery, fits on a shelf, in a closet, or behind a door.
- History up to 6 months: data remains available in the app and can be exported to compare seasons and different environments.
- Threshold-based automations: start a dehumidifier, thermostat, or ventilation when temperature or humidity go outside your set range.
- Customizable alerts: push notifications when a parameter exceeds your defined comfort value.
- White PC housing: indoor use, operating temperature −20 to 60 °C, operating humidity 5–95% RH non-condensing.
- CE, FCC and RoHS certifications: EFR32MG22 chip and 3.0 V DC input.
- Requires a Sonoff Zigbee hub: the sensor cannot connect to your home network by itself, and the bridge to Apple Home is via Matter.
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Sonoff SNZB-02M AirGuard TH, the Zigbee Sensor that Measures Temperature, Humidity, and Air Pressure
The SNZB-02M is the Zigbee 3.0 environmental sensor of the AirGuard series, and measures three quantities instead of the usual two: temperature , relative humidity and atmospheric pressure . From the read values, the eWeLink app also obtains dew point and VPD , i.e. the two indicators that really tell us whether an environment is at risk of condensation or whether a greenhouse is working well. The declared accuracy is ±0.2 °C for temperature, ±2% RH for humidity and ±0.1 hPa for pressure, with the data refreshing every 5 seconds . A CR2477 button battery keeps it powered for over two years without cables or power supply, and the 45 × 45 × 17.6 mm body fits wherever it needs to be measured. Like any Zigbee device, it does not communicate with the router on its own: it requires a Sonoff Zigbee hub to bring it to the home network, and this is the first piece to check before ordering it.
Five Environmental Values from a Single Zigbee Sensor with Silicon Labs Chip
A single device covers five indicators : temperature , humidity , and air pressure come from onboard sensors, while the dew point and VPD are calculated by the app based on those values. It's the difference between a thermo-hygrometer and a real environmental sensor : it doesn't just tell you how hot it is, it tells you what it means. At the heart is a Silicon Labs EFR32MG22 chip , the same type used in low-power Zigbee nodes, which is why a single coin cell battery lasts over two years of continuous measurements.
-€5.00
Sonoff AirGuard TH SNZB-02DR2 Smart Zigbee Temperature and Humidity Sensor with Display
Real-Time Remote Reading: Always Know the Environment Status in the eWeLink App
The five indicators can be viewed in real time from the app, from home or away, without having to be in the room you're monitoring. It's a practical way to keep an eye on a cellar , a second home , or a greenhouse while you're away, and to notice a deviation before it becomes a problem. Each value has its own threshold and notification , so you don't need to open the app to know something has changed: your phone will tell you. The history remains available to compare different days, seasons, and environments.
Accuracy of ±0.2°C, ±2% RH and ±0.1 hPa with Data Update every 5 Seconds
The numbers that matter are these: ±0.2°C for temperature , ±2% RH for relative humidity , and ±0.1 hPa for atmospheric pressure . On a barometric measurement, that tenth of a hectopascal is what makes a trend readable, because the variations that anticipate a change in weather are small and slow. The data updates every 5 seconds , so even small deviations are noted: the open window, the bathroom after a shower, the greenhouse in the afternoon sun. With a reading every few minutes, those peaks would be lost entirely.
Compact size for bedroom, bathroom, cellar, greenhouse and terrarium
The body measures 45 × 45 × 17.6 mm and weighs 27.3 g with the battery inside: it can be placed on a shelf, behind a book, inside a closet or leaning against a wall without being noticed. It is designed for indoor use and operates from −20 to 60 °C with humidity from 5 to 95% RH non-condensing , so it can also withstand environments at the extremes of the house. Living rooms, bedrooms, bathrooms , wine cellars , collection rooms, greenhouses and terrariums are places where a precise measurement really changes decisions.
The Barometric Trend Anticipates Weather Changes and Helps You Regulate Climate and Ventilation
Atmospheric pressure is the data missing from common sensors, and it's useful because it's not read in absolute terms but in terms of trend : a steady decline indicates worsening weather, a rise indicates stabilization. Knowing this a few hours in advance allows you to close a window , ventilate earlier, or turn up the heating before the indoor climate is affected. The declared operating range is from 700 to 1100 hPa , which covers everything from sea level to the altitude of a mountain house without leaving the scale.
Dew Point Indicates Risk of Condensation on Walls Before Mold Arrives
The dew point is the temperature at which air no longer retains vapor and settles on surfaces. Comparing it to the temperature of an exterior wall tells you whether that wall is about to get wet, and repeated condensation is the first step towards mold . The app automatically calculates this from temperature and humidity , so you don't have to do the math: just read one number and you'll know if ventilation is necessary. In bathrooms, cellars, basements, and poorly heated rooms, it's the most useful indicator of the three.
VPD, the Vapor Pressure Deficit that Guides Greenhouse and Terrarium Growers
VPD , or vapor pressure deficit, measures how much water the air can still absorb, and is the key indicator for regulating a greenhouse or terrarium . If the VPD is too low, the plant will barely perspire and slow down; if it's too high, it will lose water faster than it absorbs. Temperature and humidity alone don't tell you: you need to combine them, and that's what the eWeLink app does based on the SNZB-02M 's measurements. Growers read just one number instead of two and immediately know whether to ventilate or mistem.
CR2477 Button Cell Battery with Over Two Years of Battery Life and Few Replacements
The power supply is a 3V CR2477 button battery , and the declared battery life exceeds two years : no wires, no power supply, no occupied sockets near the measurement point. This is the reason why a Zigbee sensor can be placed where it's really needed, inside a closet or at the back of a cellar, rather than where there's electricity. The CR2477 is a widely available size and can be changed without tools. Such low consumption is thanks to the Zigbee 3.0 protocol , which keeps the radio off between transmissions.
Custom Comfort Thresholds for Temperature, Humidity and Pressure with Push Notification
For each parameter, you set a comfort range : the temperature between two values, the humidity below a certain threshold, the pressure inside a window. When a parameter goes outside that range, the app immediately sends a push notification , and you don't have to check anything manually. It's how you notice that the cellar has exceeded 70% humidity, that the greenhouse has dropped below the minimum temperatures, or that the bedroom has become too dry at night. The thresholds change as the season changes.
Automations that turn on the dehumidifier, fan or heating when the threshold is exceeded
The next step after the alert is automation : when the threshold is exceeded, the SNZB-02M automatically starts a dehumidifier , a fan , a thermostatic valve , or a customized scene. The sensor measures, the hub decides, and the actuator executes, so you need at least one device that can be controlled online: you can find them among the Sonoff smart switches and modules . This is how monitoring stops being a graph to look at and becomes a home that regulates itself while you're away.
Up to Six Months of Free Cloud History with Export of Measured Data
Measurements aren't just instantaneous: temperature , humidity , pressure , dew point , and VPD are stored and available as trends , with cloud storage for up to six months at no additional cost. It's more useful than it seems: compare the same room between winter and summer, check if a dehumidifier is actually working, prove that a cellar has maintained its parameters throughout the season. The data is exported , so you can import it into a spreadsheet and perform your calculations outside the app.
Voice Commands with Amazon Alexa and Google Home to Ask for Temperature and Humidity
The SNZB-02M responds to the main voice assistants : ask Amazon Alexa or Google Home what the temperature is in a room and it will tell you, without taking out your phone. This is the function that is used more often than you think, because the question comes while your hands are full. The connection still goes through the Zigbee hub and the eWeLink account: the voice assistant speaks to the service, not directly to the sensor, so an active internet connection is required.
Integration with Apple Home Using a Sonoff Zigbee Matter Bridge
Those who work at Apple Home aren't left out: Sonoff Zigbee devices enter Apple Home through a Matter Bridge , a gateway that exposes Zigbee nodes to the Matter protocol. From there, the SNZB-02M appears among the accessories along with the rest of the system and participates in system automations. It's an extra step compared to Alexa and Google, and it must be said: without a compatible bridge , the sensor on Apple Home is invisible. With that, control returns to being single and continuous.
Open Source Integration with Home Assistant and Self-Hosted Software via Zigbee Dongle
If you prefer to keep everything in-house, the SNZB-02M works with self-hosted software like Home Assistant , paired with a Sonoff Zigbee dongle that acts as a network coordinator. In that configuration, data doesn't pass through the cloud and the automations run locally, so they remain active even if the internet connection drops. This is the option for those who want local control and no dependency on an external service, and it requires a minimum amount of familiarity: setup takes longer than pairing via the app.
Available Functions According to Hub: eWeLink , ZHA, Zigbee2MQTT, Alexa and SmartThings
It's worth mentioning before purchasing: the available functions vary depending on the hub you connect the sensor to. With the eWeLink ecosystem, you have everything, including VPD and dew point , because these calculations are performed by the app; on ZHA , Zigbee2MQTT , Alexa , and SmartThings , the measured values arrive, and the rest depends on what that platform displays. Choosing the Sonoff Zigbee gateway is therefore not a minor detail: it decides what you'll actually see, and it's best to choose one with the entire network in mind, not just this sensor.
SNZB-02M, SNZB-02B and SNZB-02P Comparison on Measured Quantities, Battery and Dimensions
The AirGuard series has three versions, and they're easily confused. The SNZB-02M is the only one that also measures atmospheric pressure and uses a CR2477 battery ; the SNZB-02B is the Lite version, just temperature and humidity, powered by two AAA batteries ; the SNZB-02P is the variant with a display. They also vary in size and format, so the choice depends on the measurements you actually need and the type of battery you prefer. You can find them all among the Sonoff temperature and humidity sensors .
Three Mounting Methods: Magnetic Attachment, 3M Adhesive Plate, or Screw Fixing
Mounting adapts to the location, not the other way around: there's a direct magnetic attachment to a ferrous surface, a metal plate with 3M adhesive for attaching to a wall or piece of furniture, and a screw-on plate where the adhesive won't hold or the location needs to be permanent. The magnet is the most convenient solution because you can quickly remove the sensor to change the battery or move it to another room. The plate, adhesive, and screws are included in the package.
Technical Specifications: Zigbee 3.0, CR2477, −20 to 60°C, 700-1100 hPa, 45 × 45 × 17.6 mm
In summary: model SNZB-02M , AirGuard series, Zigbee 3.0 connection over IEEE 802.15.4 , 3V CR2477 battery power supply, white PC casing, dimensions 45 × 45 × 17.6 mm for 27.3 g with battery. Indoor use, operating temperature −20 to 60 °C , humidity 5 to 95% RH non-condensing , pressure 700 to 1100 hPa , CE , FCC and RoHS certifications. The complete rating data remain on the official Sonoff page .
What's in the Box: Sensor, Metal Plate with Adhesive, Screws and Documentation
The package includes the SNZB-02M sensor with the CR2477 battery already inserted, the metal plate with 3M adhesive , screws for alternative fastening, and documentation. The Zigbee hub is not included, but is essential and must be purchased separately if you don't already have one at home. The automation actuators are also not included: the sensor measures and reports, but to turn on a dehumidifier or a valve, you need a device that can be controlled on the same network.
Frequently Asked Questions
What is air pressure monitoring used for?
It helps you read weather trends and adjust room temperature, humidity, and ventilation accordingly. It's also useful for maintaining stable conditions when caring for reptiles, growing plants, and storing wine.
How do you read pressure to understand time?
Steadily rising pressure: improving weather, less likely to rain. Steadily falling pressure: possible arrival of clouds, rain, or wind. Rapid drop, below 2-4 hPa in three hours: possible cold front, heavy rain, or strong wind. Stable pressure: stable conditions. Pressure varies with location, altitude, and season: the rate of change is more important than the absolute value.
How do I view my dew point and VPD history?
Dew point and VPD are calculated from temperature and relative humidity and are displayed on the History page. If the curves aren't displayed, open the gear icon in the top right and activate them using the "+/−" button next to each data type.
How long does the battery last?
The SNZB-02M uses a CR2477 battery. Battery life depends on usage and environmental conditions, but is typically about two years. To maximize battery life, it's best to keep the sensor within range of your Zigbee hub, which reduces communication attempts.
Can it be used outdoors?
No. The SNZB-02M is not waterproof. SONOFF does not recommend using it outdoors or in places where it might get wet.
Do you need a Zigbee hub?
Yes. It is a Zigbee 3.0 device: to work it must be paired with a compatible Zigbee hub.
How accurate are the measurements?
±0.1 hPa for pressure, ±0.2 °C for temperature and ±2% for relative humidity, updated every 5 seconds.
What intervals does it work in?
Temperature from −20 to 60 °C, humidity from 5 to 95% non-condensing, pressure from 700 to 1100 hPa.
What size is it and how is it assembled?
45 × 45 × 17.6 mm, polycarbonate casing. It can be mounted in three ways: direct magnetic attachment, metal plate with 3M adhesive, or screw-on plate.
Sonoff-SNZB-02M
Data sheet
- Power supply
- CR2477 battery
- Colors
- White
- Material
- PC
- Working temperature
- -20℃-60℃
- Working humidity
- 5% - 95% non-condensing
- Voice Control
- Amazon Alexa, Google Home and Siri
- Mobile application
- eWeLink
- Dimensions
- 45x45x17.6mm
- Communication Protocol
- Zigbee 3.0
- Humidity measurement accuracy
- ±2% RH
- Temperature measurement accuracy
- ±0.2℃/±0.4℉
- mcu
- EFR32MG22C224F512GN32
- Features
- Air Pressure Measurement
Humidity Measurement
Temperature Measurement - Usage environment
- Indoor
- Blood Pressure Monitoring
- 700-1100 hPa
- Pressure measurement accuracy
- ±0,1 hPa
- Works with
- Amazon Alexa
Apple Home (HomeKit)
Google Home
Home Assistant
SmartThings
eWeLink (Sonoff) - Hub required
- Sonoff Zigbee hub (ZBBridge / iHost / NSPanel Pro)
- Ideal for
- Sensors & detection
- Home Assistant integration
- Cloud integration
Zigbee via dongle (ZHA / Zigbee2MQTT)
Specific References
- UPC
- 697903360070
- EAN13
- 6979033600706
- MPN
- Sonoff SNZB-02M
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- Five metrics in one sensor: measures temperature, humidity and atmospheric pressure, and the eWeLink app derives dew point and VPD.
- Stated accuracy: ±0.2 °C for temperature, ±2% RH for humidity and ±0.1 hPa for pressure.
- Pressure from 700 to 1100 hPa: barometric trends anticipate weather changes and let you adjust climate and ventilation in advance.
- Zigbee 3.0 over IEEE 802.15.4: low-power, low-latency network, with the sensor acting as a node without using Wi‑Fi bandwidth.
- Over 2 years of battery life: powered by a CR2477 3 V battery, no cables or power adapter required.
- Compact size 45 × 45 × 17.6 mm: 27.3 g with battery, fits on a shelf, in a closet, or behind a door.
- History up to 6 months: data remains available in the app and can be exported to compare seasons and different environments.
- Threshold-based automations: start a dehumidifier, thermostat, or ventilation when temperature or humidity go outside your set range.
- Customizable alerts: push notifications when a parameter exceeds your defined comfort value.
- White PC housing: indoor use, operating temperature −20 to 60 °C, operating humidity 5–95% RH non-condensing.
- CE, FCC and RoHS certifications: EFR32MG22 chip and 3.0 V DC input.
- Requires a Sonoff Zigbee hub: the sensor cannot connect to your home network by itself, and the bridge to Apple Home is via Matter.
Sonoff AirGuard TH SNZB-02M Zigbee Temperature, Humidity, and Air Pressure Sensor
€18.90
€23.90
Save €5.00Tax included
No review at the moment