Connected devices · Milesight EM300-TH
Milesight EM300-TH: temperature alerts that reach maintenance
A cold room that warms up at two in the morning is a stock written off at eight. A server room that overheats on a weekend is an outage on Monday. The Milesight EM300-TH measures temperature and humidity over LoRaWAN for years on its battery, and FreeMaint makes sure a drift reaches the right technician, with a work order on the right asset.
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In short
The Milesight EM300-TH is a battery-powered LoRaWAN sensor that measures temperature and humidity. FreeMaint decodes its messages itself when they arrive through The Things Stack, ChirpStack or a Milesight gateway. Each value becomes a channel with its history; alert rules raise an alert above or below a limit, notify the right roles in the app and by push, and can open a work order on the asset.
Updated October 16, 2026
What the EM300-TH brings to maintenance
Temperature and humidity, decoded by FreeMaint
FreeMaint decodes the sensor’s messages itself: temperature, humidity and battery level arrive as channels on the first message, with no decoder to configure on the network server.
Included in BusinessAlerts held long enough to matter
A threshold rule can require the condition to last before raising an alert, and a margin to clear stops a value hovering around the limit from flapping. A door opened for a delivery does not wake anyone up; a compressor that stopped does.
Included in BusinessA work order on the cold room, not an email
Tick Create a work order on the rule and the alert opens a work order on the asset. One alert creates at most one, and an open work order from the same rule is reused.
Included in BusinessA sensor that cannot go silent unnoticed
FreeMaint keeps the battery level, the radio signal and the last message of each sensor. Set the expected reporting interval, and a no-data rule tells you when a sensor stops talking.
Included in BusinessSupported devices
These models are recognised and decoded by FreeMaint. FreeMaint sells no hardware: each link opens the manufacturer’s own page.
- Manufacturer page
Milesight EM300-TH
LoRaWAN · Compatible
Compatible: validated on the manufacturer’s documentation. Lab-tested: tested on the physical device by FreeMaint.
Where a temperature sensor pays for itself
Cold rooms and freezers in kitchens, shops and warehouses are the obvious case: one failed compressor overnight can cost more than a whole network of sensors. Server and electrical rooms come next, where heat shortens the life of every component. Pharmacy stores, laboratories and archives add humidity to the picture.
In all these places the measurement itself is not the goal. The goal is that someone acts before the damage, and that the action is recorded: who went, what was found, what was repaired. That is why the alert belongs in the maintenance system, attached to the cold room or the air conditioner it concerns.
- Cold rooms, freezers and refrigerated display cases
- Server rooms and electrical rooms
- Pharmacy and laboratory stores, archives
- Technical rooms with sensitive equipment
How the readings reach FreeMaint
The EM300-TH sends its readings over LoRaWAN to a gateway. Your network server — The Things Stack, ChirpStack, or the server built into a Milesight UG65 or UG56 gateway — forwards each message to FreeMaint over HTTPS, with the URL and the header FreeMaint gives you when you create the connection.
Do not set a payload codec on a Milesight gateway: FreeMaint decodes the sensor itself and needs the full message. The sensor is recognised automatically and appears in Connected devices → Devices on its first message. Confirm it and attach it to the asset it watches, and its channels follow that asset.
Writing an alert rule that people trust
An alert that fires too often is soon ignored. For a cold room, set the threshold a few degrees above the set point, require the condition to last for a while so that a delivery does not trigger it, and set a margin to clear so the alert ends only once the temperature is clearly back. Choose a critical severity for the freezer that holds the most valuable stock: critical alerts are also sent by email.
Add a no-data rule on the same sensor. A sensor whose battery is empty or which lost the gateway is as dangerous as a warm cold room, because it hides the next failure. When the alert ends, it closes by itself; the work order stays open until someone has checked the equipment and closed it.
Plans and buying the sensor
Connecting devices is part of the Business plan, at $99 per month per company, flat, with 100 active channels — each EM300-TH uses a few: temperature, humidity and battery. FreeMaint sells no hardware: buy the sensor from Milesight or its distributors. It carries the Compatible badge, validated against Milesight’s documentation.
Watch a cold room in five steps
- 1
Place the sensor
Inside the cold room or the technical room, within reach of a LoRaWAN gateway.
- 2
Create the connection
In Connected devices → Integrations, click Connect a device and choose your network server.
- 3
Forward the uplinks
Paste the URL and the header FreeMaint shows into the network server’s webhook or HTTP integration.
- 4
Attach the sensor to the asset
Choose the cold room or the equipment it watches on the device page.
- 5
Add the rules
A threshold rule with a hold time and a work order, plus a no-data rule for a silent sensor.
Frequently asked questions
How long does the battery last?
It depends on the reporting interval and the radio conditions; Milesight states the figures in its documentation. FreeMaint shows the battery level of each sensor so you can replace it before it dies.
Which LoRaWAN network servers work?
The Things Stack (The Things Network or The Things Industries), ChirpStack, and the server built into Milesight UG65 and UG56 gateways.
Can an alert create a work order?
Yes. Tick Create a work order on the rule. One alert creates at most one work order, and an open one from the same rule is reused.
Who receives the alert?
The roles chosen for device alerts in the notification settings, among the people allowed to see alerts. Critical alerts are also sent by email.
Can I see the temperature history?
Yes. Each channel shows its curve from six hours to a year, and the mobile app shows the live values of an asset.
Does FreeMaint sell the sensor?
No. FreeMaint sells no hardware; the page links to Milesight’s own product page.
Related pages
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