Temperature and humidity sensor | 0-100%RH | -40-+85°C | with 52cm cable | black | SONOFF | SI7021

Temperature and humidity sensor | 0-100%RH | -40-+85°C | with 52cm cable | black | SONOFF | SI7021 1

Temperature and humidity sensor | 0-100%RH | -40-+85°C | with 52cm cable | black | SONOFF | SI7021

Code: SONOFF-SI7021

Barcode: 6920075759482

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Price 6.98 € VAT incl.

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SONOFF SI7021 is a wired temperature and humidity sensor (-40…+85 °C, 0–100 % RH) with a 52 cm cable and a 2.5 mm plug. Designed for SONOFF TH10 and TH16 controllers – it turns them into a thermostat and humidistat. Not compatible with the THR series.

Product description

Temperature and humidity sensor | 0-100%RH | -40-+85°C | with 52cm cable | black | SONOFF | SI7021

SONOFF SI7021 is a wired temperature and humidity sensor with a 52 cm cable and a 2.5 mm plug. It connects to SONOFF TH10 and TH16 controllers and lets them automatically control heating, ventilation or humidification.

Key idea:
The sensor turns a TH16 or TH10 relay into a thermostat and humidistat: the controller receives accurate temperature and humidity data and switches the load accordingly.

Measurement
temperature and humidity

Range
-40…+85 °C, 0–100 % RH

Connector
2.5 mm plug

Cable
520 mm

How it works

The sensor plugs into the 2.5 mm jack of TH10 or TH16 and is powered by the controller – no separate power is needed.

The sensing element measures air temperature and relative humidity, and the controller sends the data to the eWeLink app.

Based on these values, the TH controller in automatic mode switches a heater, fan or humidifier on or off.

Why choose SI7021?
One sensor measures both temperature and humidity, so TH16 can control both heating and dehumidification without additional devices.

Technical specifications

Product type	Wired temperature and humidity sensor for TH-series controllers
Manufacturer / model	SONOFF SI7021
Measured parameters	temperature, relative humidity
Temperature range	-40 … +85 °C
Humidity range	0–100 % RH
Accuracy	±0.4 °C; ±3 % RH
Connector	2.5 mm plug
Cable length	520 mm
Compatibility	SONOFF TH10, TH16
Colour	black
Dimensions	55 × 27 × 13 mm

Main functions

Temperature measurement – the controller manages heating or cooling.
Humidity measurement – the controller manages a fan or humidifier.
Plug-in connection – 2.5 mm plug without tools.
Powered by the controller – no batteries or separate power needed.
Data in the app – values visible in eWeLink.
Compact housing – easy to mount at the measuring point.

Where is it used?

Greenhouses and seedling rooms
Basements and storage rooms
Bathrooms and laundry rooms (in a dry spot)
Garages and workshops
Terrariums
Humidity-based ventilation control

Use by need

For homeowners.
TH16 becomes a thermostat and humidistat – the basement or greenhouse is looked after automatically.

For electricians.
Simple plug-in connection without extra wires or power.

For farm owners.
Temperature and humidity control helps protect plants and stored produce.

Practical use

If moisture builds up in the basement, SI7021 is plugged into TH16, which controls an extractor fan: when humidity exceeds 75 % the fan switches on, and at 65 % it switches off.

Pros

Measures temperature and humidity
Wide measuring range
Simple plug-in connection
No separate power needed
Compact

Cons / limitations

Fits only TH10 and TH16
Not for THR-series RJ9 controllers
52 cm cable – longer distances need another solution
Not designed for immersion in water

Safety and installation notes

Connect the sensor only to a compatible TH10 or TH16 controller
Protect from direct water exposure and condensation
Route the cable away from power cables and hot surfaces
Do not bend the cable sharply at the plug
Do not install near heat sources – readings will be inaccurate

Quick selection guide

Temperature and humidity

-40…+85 °C

0–100 % RH

2.5 mm plug

520 mm cable

TH10 / TH16

Suitable when you need:

turn TH16 into a thermostat and humidistat
control a fan by humidity
monitor the climate in a greenhouse or basement

Check before use:

whether you have TH10 or TH16 (not THR)
the distance from the controller to the measuring point
that the sensor will not be exposed to water
a measuring point away from heat sources

Important reminder: SI7021 does not fit THR316 / THR320 controllers – choose THS01, WTS01 or MS01 sensors with an RJ9 connector for them.

FAQ

Which controllers is it compatible with?
SONOFF TH10 and TH16 with a 2.5 mm jack.

Does it fit THR316 or THR320?
No, the THR series uses RJ9 sensors: THS01, WTS01, MS01.

How long is the cable?
520 mm.

Does it measure humidity?
Yes, relative humidity 0–100 % RH.

What is the accuracy?
About ±0.4 °C and ±3 % RH.

Can it be used outdoors?
Only in a sheltered place protected from direct rain and water.

Temperature and humidity sensor | 0-100%RH | -40-+85°C | with 52cm cable | black | SONOFF | SI7021

SONOFF SI7021 is a wired temperature and humidity sensor with a 52 cm cable and a 2.5 mm plug for TH10 and TH16 controllers: -40…+85 °C, 0–100 % RH, for automatic heating and humidity control.

Illustrative image may have been created using AI. The appearance of the product may differ slightly from the image shown. Please refer to the technical specification.

Attributes

Manufacturer

Sonoff

CE certificate – a guarantee of safety, quality, and compliance

This product is marked with the CE label, which confirms that it complies with all applicable European Union directives and regulations. CE marking is not just a formality – it is an important indicator of quality and safety, ensuring that the product has been properly assessed, tested, and can be safely used throughout the EU market.

CE certification means that the product has been evaluated according to the main criteria:

Safety requirements – ensures that the product does not pose a risk to the user or the environment
Electromagnetic compatibility (EMC) – the device does not interfere with other equipment and is resistant to external disturbances
Environmental standards – complies with current ecological and material usage requirements
Operational reliability – the product is suitable for long-term use according to its intended purpose

CE marking allows this product to:

be legally supplied and used in all European Union countries
ensure a high level of quality and safety
be used in residential, commercial, and industrial environments

The CE mark is a declaration of the manufacturer’s responsibility, confirming that the product complies with all applicable standards and has been assessed according to EU legislation.

What does this mean for you as a buyer?

Safe use in everyday activities
Reliable performance and reduced risk of failure
Compliance with EU standards and requirements
Suitability for professional solutions