Here at GridLocate Ltd, we get a lot of enquiries regarding LoRaWAN Temperature Sensors. Through our partnership with Zane, we’re able to recommend different Temperature Sensor solutions based on the customer project. There are a number of parameters to consider when buying LoRaWAN Temperature Sensors:
a.) What is the range of temperature you wish to monitor (room temperatures, refrigeration units, e.t.c)_
b.) What accuracy do you require? Is +/- 0.5, or 1C acceptable
c.) How quickly do you need the sensor to respond to change? In seconds, minutes?
d.) Where will it be located? Does it need to have an external metal probe, or internal and waterproof?
The thing is, there’s a lot of temperature sensing components on the market, and not all of them respond or operate in the same way. The majority of LoRaWAN sensors use the ST21 or DS18B20 sensors, and these are great for your every-day monitoring application. The DS18B20 is responsive to daytime temperatures and accurate to +/- 0.5C down to 10C. According to their tech team, you’ll get a response and accurate reading within 2 minutes of an environmental change.
Temperature Sensor Tests
For our own sanity, we’re interested in testing how our LoRaWAN temperature sensors operate and respond to cold temperature. We conducted a short test, moving the sensors from room conditions to the freezer and then to fridge. We set the devices to transmit every minute and recorded the results. Please note: These are NOT laboratory test conditions. No people in white-coats, no certification and micro-calibrated units. You can get the sensor specifications from the manufacturers to understand the design parameters, but we were interested in real-world DIY testing. Our own calibrated sensor, our standard consumer LG freezer and fridge and our Zane temperature sensors.
Results: We’re really impressed. Let’s explain the graph.
The dotted blue line is our control, using an off-the-shelf calibrated temperature reader. The green line is our zTemp-IP65 with an external temperature sensor. The red and brown are a couple of competitor products.
We believe the results demonstrate that the zTemp performs well against our competitors. It is responsive to temperature changes down to -20C. Its accuracy is within the tolerance described by the temp component manufacturers, and our device reacts nicely to both drops and increases in temperature.
Particularly interesting is the 3rd party ST31 chipset. We do NOT think this is an issue with the sensor chip, as the ST31’s are known to be a very accurate and reliable chip. Instead, we think this is down to the position of the chip within the device, and the type of enclosure used.
Lessons learnt for the future, is that metal-probe based temperature sensors outperform board-based sensors, and that special attention has to be given to the enclosures around temperature sensors.
If you’d like to discuss your LoRaWAN Temperature Sensor project, drop us a line at [email protected]
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