On 31/12/2018 10:36, Jan Panteltje wrote:

> Maybe something like this:
>    http://www.ebay.com/itm/263367772077
>
> A
HFS-DC06-5-8GHz-Microwave-Radar-Sensor-Module-DC-5V-ISM-Waveband-Sensing-12m
> Only 5$ inclusive shipping
>
> Range 12 meters, 360 degrees, maybe add some parabolic antenna to narrow the
angle.
>
> ebay is full of things like that.


I have recently replaced my oil tank sensor.

Its a 433Mhz thing that uses an ultrasonic beam to detect oil height.

It is allegeldly linux readable using software defined radio dongles
designed for DVB-T reception.

It is however very narrow beam ultrasonics and does not really like
anything but a plane surface at right angles.

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