Bluetooth between sensor and data logger
Bluetooth is used for the sensing itself, not for the gateway. That is what allows a sensor to sit inside the equipment without a cable through the door seal.
What is Bluetooth used for in a monitoring system?
For the short link: from the sensor to the data logger. The sensor pairs wirelessly with the logger and sends its readings there at a fixed interval. From there they go on over LoRaWAN to the gateway.
It is a common misunderstanding that Bluetooth is used all the way. It is not, and it would not work either, because the range is too short. Bluetooth solves the problem that a cable from sensor to logger cannot always be run. We do that with Emerald, which is our only wireless sensor.
Emerald also has another use. The sensor can store the readings itself, and Bluetooth is used to read it with a phone, typically when a shipment has arrived.
The range between sensor and data logger is short on purpose. They are placed together at installation.
Where Bluetooth is used
Inside closed cabinets
Where the door seal must not be broken, and a flat cable is not an option.
In cleanrooms
Where a cable penetration in the wall is a change that has to be documented.
In shipments
Emerald measures all the way and is read with a phone over Bluetooth on receipt.
Behind equipment
Where a cable would be in the way or cannot be routed neatly.
During sensor exchange
The new sensor is paired, and the logger reads the calibration data directly.
For on-site reading
The readings can be retrieved on a phone without going through the system.
Bluetooth is not the gateway
It is worth keeping the two apart, because they each solve their own problem. Bluetooth covers the few metres between sensor and data logger. LoRaWAN covers the distance from the data logger to the gateway, which can be hundreds of metres through a building. A solution that used only Bluetooth would require a receiver in every room.
Read about LoRaWAN →Frequently asked questions
How far does Bluetooth reach?
A few metres, and that is on purpose. Sensor and logger are placed together at installation.
Can we read a sensor with a phone?
Yes. Emerald can be read either via Bluetooth on the phone or directly on the data logger, depending on the setup.
Is there a battery in the sensor?
Emerald Bluetooth sensors have a battery, and the system gives a technical alarm in good time. Cabled and cable-free Smart-Sensors are powered through the data logger.
Is the measurement as accurate as with a cable?
Broadly, yes. We are happy to send the specifications on request.
Can the Bluetooth sensor sit in a freezer?
Yes, within its measuring range. For -80 and below, a Pt100 probe is used.
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