Electronics help. What size resistor's please.

[collectors]

Ok! slightly off topic, but thought there might be some electronic help here. I have 2x1500 lt water tanks in my garden that are linked & wanted a water meter/gauge. So the idea is, like the image, but not sure what size resistors to fit in items 1 to 5. Should they all be just one value ? or somthing different & is 5 needed?. Thanks
PS: lets say its for a 3000lt steam engine water tower.

 

[PhilP]

Really need to know whether your switches are normally open, or normally closed. Or whether the meter works backwards?
Spec. of the meter would also be useful.

Alternately, an elbow fitted low on the tank. A vertical length of clear pipe, and a float (ball or Cork) in the pipe.
No electricity required.


PhilP

 

[collectors]

Really need to know whether your switches are normally open, or normally closed. Or whether the meter works backwards?
Spec. of the meter would also be useful.

Alternately, an elbow fitted low on the tank. A vertical length of clear pipe, and a float (ball or Cork) in the pipe.
No electricity required.


PhilP

Normally open with no water. I would assume the more resistance the lower the reading. But this could be tried with two resistors as an experiment to see. But do you think to just try 5 x 38ohm resisters to see. Glass tube is a good idea, but wont work on my remote panel. lol

 

[Greg Elmassian]

The resistors will not all be the same, since the lower switches are on.

the SUM of the switches on at one point is what you want to know, so each successive resistor will be different.

So first, you need to figure out what you want to do, you did not write this down.

Your presentation shows that you could have 5 different readings.

So empty would would be one, then 1/4, 1/2, 3/4, full is what I would suggest.

The easiest way would be to apply voltage to the meter, and measure what voltage it needs for these indications, but you also need to measure the current at these points also. Then you can simply use ohms law.

Alternatively, measure the current at the extremes and get trim pots for all 5 resistors and then dial it in as you want. Very few calculations.

All depends on the effort you want to go to in order to characterize the meter.

Greg

 

[GAP]

The resistors will not all be the same, since the lower switches are on.

the SUM of the switches on at one point is what you want to know, so each successive resistor will be different.

So first, you need to figure out what you want to do, you did not write this down.

Your presentation shows that you could have 5 different readings.

So empty would would be one, then 1/4, 1/2, 3/4, full is what I would suggest.

The easiest way would be to apply voltage to the meter, and measure what voltage it needs for these indications, but you also need to measure the current at these points also. Then you can simply use ohms law.

Alternatively, measure the current at the extremes and get trim pots for all 5 resistors and then dial it in as you want. Very few calculations.

All depends on the effort you want to go to in order to characterize the meter.

Greg

Good suggestion Greg that way the meter can be calibrated.

 

[Greg Elmassian]

I think the clue is that the meter has a working range, it is not "calibrated" for "full scale at 12 volts" or similar.

Anyway, will be interested how this project proceeds.

I'm guessing it is a simple meter, no real "smarts".

Greg

 

[GAP]

Perhaps I should have said the meter inputs can be calibrated.

 

[Software Tools]

This would probably be easier....