At 12:46 PM 29/11/2004 +0200, you wrote:
>hello,
>
>I want to know how much oil goes for my house heating.
>Oil flows via 10mm pipe from tank to burner (burner 'sucks' oil from
>tank).

You could make a very accurate measurement using a small pump, two extra
small tanks, and a few opto sensors. If you feel like the heath robinson
approach, it's also cheap.

I presume your feed is a siphon out of the main tank as shown below. Move
your feed point to small tank B. Oil is pumped to tank A until full,
whereupon it drains into tank B. Tank A is calibrated, maybe 300mL. You
keep tank B full by delivering measured tots all day.

existing setup;

    |------------
|   |  |        |
|   |  |        |
|   |  |        |
| oil  |        |
 ------         |
                |____ to burner


new set-up  ( X= electric valve)

    |------X----|     
    |             ___ opto full sensor
    |          | |
   PUMP        | |    measuring tank A
    |           X 
|   |  |      |   | __ opto full sensor
|   |  |      |   |   
|   |  |      |   |    gravity feed tank B
|   |  |       ---
|      |        |
 ------         |
                |____ to burner

PUMP can be a homemade peristaltic pump


Also, 
If you use a peristaltic pump, you can do it another way by calibrating
pump the as follows;

    |--A--------------|     
    | opto            |  
    |                 B  opto   
   PUMP               |
    |              
|   |  |            |   | __ opto full sensor
|   |  |            |   | 
|   |  |            |   |    gravity feed tank
|   |  |             ---
|      |              |
 ------               |
                      |___ to burner

Use a stepper motor to drive the pump
The pipe between A and B should be ~5mm and the volume can easily be
accurately measured.
The method is to pump until fluid is sensed at B. Now reverse the pump
direction and count steps until sense at A. You now have steps/mL. Now pump
foward until the gravity feed tank is full. The calibration can be re-done
every half hour to cater for viscosity changes, pump wear.

While waiting for the gravity tank to drain, you could pump to B, add ten
steps, then hold. If opto B goes clear, then it's sucking back, and the
pump or tubes are leaking, and need repair. The drip point at the end
should be a U bend pointing upwards to prevent drain-out of the tube.

Friday night rambling. I should be out partying!


Regards
Roland Jollivet

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