EM300-TH vs EM320-TH vs AM102 vs AM103: Which Milesight Temperature & Humidity Sensor?
Short answer: buy the EM300-TH (£38.90 ex VAT) for anything outdoors, damp or unheated — it is IP67 sealed. Buy the EM320-TH (£41.90) for food areas, cold rooms and washdown environments — same sealing in a food-grade housing with a magnetic mount. Buy the AM102 (£47.88) for plain indoor monitoring in offices, classrooms and plant rooms, and the AM103 (from £127.19) when the room’s occupants need to see the reading on an e-ink display and you want CO₂ as well.
All four are LoRaWAN (EU868), run for years on batteries, and work with any LoRaWAN network server — including the embedded server inside Milesight’s UG63, UG65 and UG67 gateways, so a small site needs no software subscription at all.
The comparison
| Model | Price (ex VAT) | Where it belongs | Sealing | Extras |
|---|---|---|---|---|
| EM300-TH | £38.90 | Outdoors, warehouses, unheated buildings, cold chain | IP67 | External-probe variants in the EM300 family |
| EM320-TH | £41.90 | Food production, commercial kitchens, cold rooms | IP67, food-grade housing | Magnetic mount for racking and stainless surfaces |
| AM102 | £47.88 | Offices, classrooms, plant rooms, landlord compliance | Indoor | AM102L variant £38.90 |
| AM103 | from £127.19 | Meeting rooms and classrooms where people act on the reading | Indoor | E-ink display; CO₂ on AM103 (AM103L omits it) |
How to choose in 30 seconds
- Is it wet, cold or outdoors? EM300-TH. It is the workhorse: damp cellars, loading bays, glasshouses, container monitoring.
- Is it a food environment? EM320-TH. The housing is designed for washdown and it sticks magnetically to racking — no drilling in an EHO-inspected area.
- Is it a normal room? AM102. Cheapest path to damp/mould evidence for landlords and facilities teams.
- Do occupants need to see the number? AM103. The e-ink screen shows live readings, and the CO₂ channel doubles it as a ventilation check.
What people miss
Accuracy is the same class across all four (±0.2–0.3 °C), so paying more does not buy a better thermometer — it buys the right housing and the right extras. The money question is the environment, not the spec sheet.
Battery life depends on reporting interval. At the default 10-minute interval all four run for multiple years; pushing to 1-minute reporting for cold-chain compliance shortens that. For legionella-style weekly evidence, hourly is ample.
You need a gateway. One UG63 (£98.76) covers a small building; a whole estate typically runs on a single UG67. Sensors without a gateway log nothing.
Every product above is UK-stocked with published pricing. Ask for a trade quote for volume, or call 023 9223 3611.
The short answer
Which Milesight temperature and humidity sensor should I buy?
Choose by environment, not by spec. The EM300-TH (£38.90 ex VAT) is IP67 for outdoors, damp and unheated spaces; the EM320-TH (£41.90) is the food-grade version for kitchens and cold rooms; the AM102 (£47.88) covers ordinary indoor rooms; and the AM103 (from £127.19) adds an e-ink display and CO₂ where occupants need to see the reading.
Frequently asked questions
Do Milesight sensors work without a subscription?
Yes. Milesight gateways include an embedded LoRaWAN network server, so readings can go straight into your own systems over MQTT or HTTP with no monthly platform fee.
Which Milesight sensor is right for a cold room?
The EM320-TH for the room itself — it is food-grade and magnetically mounted. Use an EM300-TH external-probe variant where you need the probe inside a freezer cabinet.
Can I mix different sensor models on one gateway?
Yes. Any combination of LoRaWAN sensors shares a single gateway, and most deployments mix models freely.
How accurate are they?
All four are the same accuracy class, roughly ±0.2–0.3 °C. Paying more buys the right housing and extras, not a better thermometer.
How long do the batteries last?
Several years at the default 10-minute reporting interval. Reporting every minute for cold-chain compliance shortens that; hourly reporting for legionella evidence extends it.
Related
Buying this in the UK
- Supplied by Indiott, a trading name of PSI Technologies Limited (Companies House 03689664, VAT GB 730 2340 83), Hampshire, United Kingdom.
- Every price is published ex VAT at indiott.com — no quote needed to see it.
- Typically dispatched within 14 working days from the UK, on a VAT invoice.
- Call 023 9223 3611 or request a quote.
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