Joined: 16 Jan 2006 Posts: 2483 Location: Queensland
Posted: Mon Oct 13, 2008 7:18 am Post subject: Oil/Petrol level sensing with ultrasonics
There are commercial systems which will do this, but they need careful setting up to avoid spurious and multiple reflections from tank supports and the roof.
Ultrasonics sounds good until you go into the details, and you find the speed of sound varies with all sorts of odd parameters ( pressure, temperature, composition of the vapour above the fluid, etc )
My preferred method would be to use a pressure sensor at the bottom of the tank. Good sensors are available from eg Freescale. _________________ Adrian Jansen
Computer language is a framework for creativity
Posted: Wed Oct 15, 2008 3:44 am Post subject: IS rating
As an instrument tech for years, I agree with adrian.
Just as a thought, bear in mind the need to protect the liquid from explosion caused by senor failure. Even earth potentials can cause explosions. Most fuel systems are classified as intrinsically rated. IS rating.
Its hard to comment without seeing the system .
I have see less sophisticated systems work well. One fuel system had a glass tube on the outside with a float and magnet on the float. Outside the tube was an array of "reed" switches. This gave a reasonable level indication for 10 levels, including a PLC trip point.
It gave electrical isolation and did the job.
Posted: Wed Oct 15, 2008 3:44 am Post subject: IS rating
As an instrument tech for years, I agree with adrian.
Just as a thought, bear in mind the need to protect the liquid from explosion caused by senor failure. Even earth potentials can cause explosions. Most fuel systems are classified as intrinsically rated. IS rating.
Its hard to comment without seeing the system .
I have see less sophisticated systems work well. One fuel system had a glass tube on the outside with a float and magnet on the float. Outside the tube was an array of "reed" switches. This gave a reasonable level indication for 10 levels, including a PLC trip point.
It gave electrical isolation and did the job.
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