Remote Temperature Sensor

This remote or wireless temperature sensor (DTM) is developed for monitoring the temperature in a process at places out of reach of other sensors.

Like Infrared-sensors, temperature can be sensed from a distance, but this sensor needs no optical visibility of the measured object. The signal is sent by modulation of a high frequency magnetic field. This field will penetrate most liquids or substances and can only be screened by a metal surface.

The sensor itself consists only of two passive components and contains no active electronic components.
The cheap sensor can be considered as disposable when produced in high quantities. Regaining the sensor from the process is not needed. The size is 5 to 20 mm, dependent upon necessary detection distance. The maximum detection distance is about 10 time the size of the sensor.

For extreme high temperatures outside the range of other datatransmitters or dataloggers (till 500 degrees), special sensors can be constructed.

Specifications:

• Temperature: - 50 till + 200 degrees
• Accuracy : 1k for absolute measurement: till 0.1 K for temperature changes.
• Measuring distance: 50 mm to 200 mm depending on size of sensor.
• Sensing speed : 10 ms (for monitoring fast moving objets).

Applications:

• Temperature control in hermetically closed chemical processes.
• Monitoring temperature-progress in a glue-process.
• Temperature control in concrete work.
• Sensing temperatures in rotating machines and brakes.
• Monitoring in food-supply

Patent on the wireless temperature measuring method has been granted. Patent-number: NL1015906

 

Prototype:

The temperature of the small sensor shown (5mm) is measured continuously via the antenna. The passive antenna is connected with a BNC-cable to the measuring equipment.
Temperature is visible on a 4 segment Led-display, and can be sent to a PC as a PWM-signal. For absolute and precise measurement, the equipment needs to be calibrated first.