Ultrasonic liquid level scored off eBay!

Check out the new toy I purchased for only $0.99 + $10s/h on ebay (retailed for $300+).



This sensor is supposed to be used to monitor fuel/water/waste tanks in yachts. I am going to use it to measure the liquid level of my new HLT.



The bottom of the unit has the ultrasonic head which sends out a series of pulses then listens for the pulses to return after bouncing off the liquid. It measures the time between the pulses to determine distance, and therefore liquid level. The sensor performs all the math and temperature correction.



The wood block is a simple test fixture I put together to see if the sensor actually functions... I found it works perfectly!!

As the liquid rises from empty to full the sensor outputs current from 4 to 20mA. I put a 250ohm resistor in series with the output and measure the voltage across it. When my HLT is empty it measures 1V and when it is full I measure 5V. Couldn't be easier to interface to a microcontroller. I plan to mount it to a pot lid that I haven't purchased yet. Best $11 ever.

interesting...

I had originally planned on making my own sensor using a bare-bones transducer module (basically the guts from a car's backup sensor head):



However, the amount of work to actually make the sensor useful was extremely large. The complete unit I purchased took all of 5 minutes to calibrate and use.

Is there company and model info on that thing?

edit:
nevermind that

have you been able to test how accurate that is?

ha! i had one of those exact things at my desk about 4 years ago. when i moved to a new desk I binned it....

i used a really nice ultrasonic sensor from endress+hauser for a project once. unfortunately it was only on loan...