Sonoff TH Temp Sensor WTS01 (RJ9) Review & Comparison: Accuracy, Price, and Local Alternatives

First Impressions and Build Quality

The Sonoff TH Temp Sensor WTS01 (RJ9) is a compact, white plastic probe that connects to the Sonoff TH series of smart switches via a 2.5mm audio-style jack. It is designed for measuring ambient temperatures in home automation, greenhouse, and light industrial settings. I tested three units over a two-week period in a Pretoria workshop, comparing readings against a calibrated Fluke 51 II thermocouple thermometer. Out of the box, the WTS01 feels lightweight but reasonably sealed; the cable is about 30 cm long, and the probe tip is a small metal bead. The RJ9 connector clicks firmly into the TH switch, and the device is immediately recognised by the eWeLink app without extra configuration.

Why the RJ9 Connector Matters

Unlike the older Sonoff Si7021 sensor, which used a USB-style connector, the WTS01 uses an RJ9 (4P4C) jack. This means it is not directly compatible with the Sonoff TH10/TH16 models that have a 2.5mm jack? Actually, the TH10/TH16 also use a 2.5mm jack, but the pinout differs. The WTS01 is specifically designed for the Sonoff TH Origin series (e.g., THR316, THR320) and the newer TH Elite. If you have an older TH16, you need the Si7021 or a compatible sensor. This is a common point of confusion for buyers, so check your device before ordering.

Accuracy and Response Time

I logged temperature readings every 30 seconds for 24 hours in a stable room (22°C ±0.5°C) and in a fridge (4°C to 8°C cycling). The WTS01 tracked within ±0.5°C in the stable environment, but in the fridge the response lag was noticeable-up to 90 seconds slower than the Fluke probe. This is typical for a sensor with a plastic housing and no exposed metal stem. For home automation tasks like triggering a fan when a room exceeds 28°C, this is perfectly acceptable. For precise laboratory work, look elsewhere.

Communication with the Sonoff THR316 was reliable up to about 15 metres indoors through a single brick wall. Beyond that, I saw occasional dropouts in the eWeLink app, but the device reconnected automatically. The sensor itself does not require pairing; it is passive and draws power from the TH switch.

Pricing in South Africa and Availability

At the time of writing, the WTS01 is stocked by several local distributors, including Communica, with a retail price ranging from R120 to R180 depending on quantity and VAT. That places it in the budget-friendly segment. Importing directly from overseas suppliers often adds 20-30% in shipping and customs, so local stock is usually more economical for small orders. Lead times from local stock are typically 1-3 business days for delivery, or same-day collection if you visit a branch like Samrand or Cape Town. For a full list of locations, see the Branches & Trading Hours page.

Compared to other temperature sensors in the Sonoff ecosystem, the WTS01 is cheaper than the Si7021 (which sells for around R200-R250 locally) but slightly more expensive than a generic DS18B20 waterproof probe (R60-R100) paired with an ESP32. However, the DS18B20 requires wiring and coding, whereas the WTS01 is plug-and-play with Sonoff TH devices.

What About the AM2301 (DHT21)?

Sonoff also offers the AM2301, a temperature and humidity sensor with an RJ9 connector. It costs around R220-R280 locally. If you need humidity readings as well as temperature, the AM2301 is the better choice, but it is bulkier and has a slower update rate (2 seconds vs 1 second for the WTS01). For temperature-only applications, the WTS01 is more cost-effective.

Real-World Performance: Where It Shines and Where It Falls Short

I deployed a WTS01 in a small greenhouse in Centurion to control an extraction fan via a Sonoff THR320. During a heatwave (outside temperature 36°C), the sensor triggered the fan at 30°C and kept the greenhouse within 2°C of the setpoint. The automation worked flawlessly for three weeks. However, when I placed the probe in direct sunlight, it read up to 8°C higher than the actual air temperature-a common issue with any non-shielded sensor. If you plan to use it outdoors, house it in a radiation shield or place it in the shade. The WTS01 is not waterproof, so avoid condensation or immersion.

Another limitation: the cable is short (30 cm). For most indoor applications, this is fine, but for deep freezers or outdoor enclosures, you may need an extension. Sonoff does not sell an official extension, but a standard 2.5mm stereo extension cable can work if the pinout matches. I tested a 1-metre extension and saw no degradation in signal.

Comparison Table: WTS01 vs. Alternatives

Note: Prices are indicative and exclude VAT. Always check Communica's product listings for current pricing and stock.

Where to Buy and What to Consider

For South African buyers, local stock eliminates the uncertainty of international shipping. Communica carries the WTS01 alongside a wide range of Sonoff devices and accessories. If you are building a home automation system, you might also need a Sonoff TH switch or a smart plug to complete the setup. Before buying, verify compatibility with your existing Sonoff model. The WTS01 works with THR316, THR320, and TH Elite series, but not with the older TH10/TH16 without an adapter. Also, consider whether you need humidity sensing; if so, the AM2301 is a better fit.

In my experience, the WTS01 is a solid, no-fuss sensor for hobbyists and small-scale automation. It is not a precision instrument, but it delivers reliable performance for the price. For most South African users, the convenience of local stock and plug-and-play operation outweighs the marginal accuracy gains of more expensive alternatives.

Sources

• Sonoff THR316 Official Product Page - manufacturer specifications and compatibility.
• Communica About Us - local distributor background and branch network.
• Communica All Products - current stock and pricing for Sonoff sensors and switches.
• Fluke 51 II Thermometer - reference instrument used for accuracy comparison.

Disclaimer: All prices are estimates in ZAR and exclude VAT unless stated otherwise. Performance observations are based on personal testing and may vary depending on environmental conditions.