KelvinTag Wireless Temperature Sensor
That is €2.72 per month, per unit. What is a lost cold room worth?
The sensor is bought once: this is its price spread over its 3-year warranty (€2.27 excl. VAT). There is no subscription.
The KelvinTag wireless temperature sensor monitors your cold chain continuously, with no subscription. Accuracy to ±0.05 °C, 3 years of battery life, IP68 waterproof. An Android phone works as a free gateway, with the 5G Poliponet gateway available as an option. Inspection-grade, and ready for an official inspection.
One-time purchase, no subscription
- Use a phone as the gateway, for free. 5G gateway optional for larger sites.
- 3-year warranty covering the battery running down before term. Physical damage is not covered.
- Returns within 7 days; return carriage at your expense.
- Inspection-grade: high-precision sensor, DGCCRF inspection-ready.
- You own the sensor. No recurring per-sensor fee.
Specifications
- Weight
- 18g
- Accuracy
- up to ±0.05 °C
- IP rating
- IP68
- Dimensions
- 55x32x18mm
- Battery life
- 3 years
- Connectivity
- Bluetooth Low Energy
- Temperature range
- -40 °C to +85 °C
Frequently asked questions
Is there a subscription to pay?
No. You buy the sensor once, with no subscription, and the apps are free. Only the Poliponet 5G gateway is charged monthly, and it remains optional.
Is the dashboard free, and does it stay free?
Yes, the dashboard is free for life. You buy the sensor once; there is no software subscription, per sensor, per site or per user. Only the optional Poliponet gateway is charged monthly.
What do I need besides the sensor?
An Android phone to act as the gateway, with the free KelvinTrack app from Google Play and an internet connection, over WiFi or mobile (5G/LTE-M). An old Android phone sitting in a drawer will do. For a larger site, the Poliponet 5G gateway is available as an option, monthly and with no commitment. Android 12 or newer is required.
I've only got an iPhone, can I use KelvinTrack?
Yes, for the dashboard: open kelvintrack.com in Safari and choose 'Add to Home Screen' to install the web app. Temperature alerts arrive as Web Push notifications, supported on iPhone from iOS 16.4. The gateway role, which reads the sensors over Bluetooth, does need an Android phone.
How many sensors can one phone track?
At least 7 sensors per phone, guaranteed. The Poliponet 5G gateway handles up to 100.
What happens if the gateway loses its internet connection?
The phone gateway needs an internet connection to send alerts: without one, no alert goes out. The sensor itself keeps recording to its memory and blinks red at the appliance as soon as its reading leaves the range. The Poliponet gateway carries its own SIM, so it does not depend on the site's WiFi. No readings are lost: as soon as the connection returns they upload, and the matching alerts reach you.
Is the range enough for a cold room?
Yes, in most cases, including a cold room or an industrial refrigerator. If your site is very spread out, a second phone gateway or the Poliponet gateway covers the distance. If the sensor goes out of range it keeps recording to its own memory and reconnects on its own once back in range: the missing readings upload with no intervention.
How accurate is the sensor?
KelvinTag is ultra precise, up to ±0.05°C. Every sensor is calibrated before it ships.
Does the sensor arrive calibrated?
NIST traceability comes from manufacturing. A documented calibration is optional: when a sensor has one, the application shows its calibrated accuracy; otherwise it shows the estimated accuracy. An annual calibration service is available.
How long are my readings kept?
The sensor holds 3 years of measurements in its own memory, and our servers apply the same 3-year retention.
Can I use it in a freezer?
Yes. KelvinTag works from -40°C to +85°C, and it is rated IP68.
How long does the battery last, and can I replace it?
The battery is guaranteed for 3 years and typically lasts longer. It is neither replaceable nor rechargeable.
What warranty comes with the sensor?
KelvinTag comes with a 3-year warranty, covering premature battery depletion. Physical damage is not covered.
Can I send it back if it isn't right for me?
Yes, you have 7 days to return it. Return carriage is at your expense.
Where do you deliver, how long does it take and what does it cost?
Delivery is by Colissimo Domicile, within mainland France. Allow 1 to 2 working days to prepare the order, then 1 to 2 working days for delivery. Delivery is free above €100. Deliveries start at the end of October 2026.
How can I pay, and is it secure?
You pay online, with secure payment through Stripe.