<snip>I also tought of hooking up a float to a variable resistor, but I don't know If I will be getting a linear graph as someone has told me that, thats not linear even when using single turn potentiometer.

Since it appears that this thread has veered in the direction of pressure sensors this may not be timely but I thought I'd clarify it anyway. Audio pots have a logarithmic taper to mimic the properties of the human ear. Pots used for instrumentation are usually linear taper. This includes single turn pots.

 

I tried to steer it to load cells, the "state of the art" for this. Non-contact, no calibration of vessel shape, dead accurate and precise, easy maintenance, tons of choices, on and on. You can buy a 50kg digital scale for under $10. No-brainer, IMHO.

 

You can buy a 50kg digital scale for under $10. No-brainer, IMHO.

(Sorry for the tangent) Have you used anything like that? (Real world experience) I've had several occasions to use a cheap load cell, and have never found a reasonably priced way to make a load cell either from parts or hacked electronics. I'd love to hear any ideas you might have on reasonably priced load cells. I've always seen prices like this for sensors and dropped the idea on economic grounds.

 

I tried to steer it to load cells, the "state of the art" for this. Non-contact, no calibration of vessel shape, dead accurate and precise, easy maintenance, tons of choices, on and on. You can buy a 50kg digital scale for under $10. No-brainer, IMHO.

No argument wayneh. I think it's the right direction too. Heck, for $10.00 it is a no brainer! I just wanted to clarify and answer the linear pot question by the OP. I didn't want Noobs, reading this thread, to think that all single turn pots are non linear.

 

I tried to steer it to load cells, the "state of the art" for this. Non-contact, no calibration of vessel shape, dead accurate and precise, easy maintenance, tons of choices, on and on. You can buy a 50kg digital scale for under $10. No-brainer, IMHO.

The OP is looking for a voltage output proportional to water level to feed into a uC. Posts #1, #9 and #16. Generally load calls are not cheap. The fishing scale is great, but I doubt there's an analog output. It may even be a spring scale with a rack and pinion encoder wheel...like some bathroom scales.

Back to the pot concept. A 10-turn linear pot with a cable drum, a float and a counterweight.

Ken

 

The fishing scale is great, but I doubt there's an analog output. It may even be a spring scale with a rack and pinion encoder wheel...like some bathroom scales.
Ken

Ken, I'm not as sure about that as you are. My wife belongs to one of those product testing organizations. Cooking stuff mostly. Every once in a while they send her a cheepy gift thingy for her participation. Most of what she's received has been eeh but the one nifty thing she got was a digital mailing scale and she loves it, me too. I didn't open it (she may kill me) but from what I can see the platen seems to not move at all. So, I doubt that there are any moving parts in it. Lets face it. Mechanicals are far more expensive to produce than electronic equivalents, if available.

Chris

 

Scale technology keeps advancing. You can buy a nice bathroom scale that measures weight to ±0.2lbs, measures moisture and fat composition, all for $30 or so. And they work great.

The point about needing analog output is a wrinkle. Lab equipment often has digital output these days but the cheap "kitchen" options or postal scales likely don't have anything but the LCD readout.

 

As microcontroller I will be using an 8051 and I would like to ask if the MPX2010GP 10kPa, be a good solution for my application as I don't know how to choose them and to know about it I need to test it myself.

http://octopart.com/mpx2010gp-freescale%2Bsemiconductor-800865

And would it be able to measure that small amount of water please>?
Thanks in advance
Regards
FiatUno

Should be fine. The output is 2.5mV per kPa so you may need an amplifier depending on what resolution you require from your ADC. This may be 1.25mV per kPa with a 5V supply voltage.

1 kPa is equal to 101.972 mm of water height.