Water level sensor

[Nickb1969]

Hi guys,

I have been looking at water level sensors and there are plenty around very cheap. I would like to built one that has a user set sensitivity. I am sure you all know the water purity and conductivity go hand in hand.

I would like a circuit that has 3 settings. 0.5 micro Siemens, 1 micro Siemens, and 2 and above micro Siemens. I would also like a relay output and green led for in water and red for not in water.

The units on eBay have the relay but none have the sensitivity setting. Most seem to use the 555 IC a series of resistors, capacitors and diodes. I only need one probe, so not high, low, just single point.

Does anyone have and ideas. Thanks in advance

 

[Bluejets]

Are you looking for water level (as in heading) or conductivity (as in description)...?

 

[Nickb1969]

I am looking for single point water detection that has selectable sensitivity.
Thanks

 

[davenn]

I am looking for single point water detection that has selectable sensitivity.
Thanks

so why the need for sensitivity if you are wanting level ( in a tank or other water container) ?

please explain more clearly
Level and sensitivity detection are two very different things

 

[Nickb1969]

so why the need for sensitivity if you are wanting level ( in a tank or other water container) ?

please explain more clearly
Level and sensitivity detection are two very different things

The sensitivity setting is to do with the application. In standard tank based applications, the conductivity of the water is fairly similar but when you go to applications where pressure and temperature is a consideration, water conductivity changes (power generation).

Gems series 16M modules come in a variety of levels for different water purity applications. 4.7k, 10k et upto 1M. I am trying to replicate something similar that has these as a selectable option rather than a factory set one.

Thanks

 

[hevans1944]

Are you thinking of measuring current between two probes with variable sensitivity to the conductivity? An auto-ranging circuit would seem to be appropriate for this. Use solid-state analog switches to control the sensitivity, or perhaps use DIP switches to set the sensitivity if the water conductivity doesn't change much for a given installation. Biggest problem might be finding or building a reliable probe that doesn't corrode during use and change its sensitivity.

I have used digital water-purity instruments that autorange and display the conductivity in Siemens. These had platinum probes IIRC. I wouldn't dream of hacking such an instrument to get a GO/NO-GO level-sensing output, but that is an option you might consider if you don't want to re-invent the autoranging conductivity meter wheel.

You might consider the frustrated internal reflection option. This involves an illumination source (LED), a photo-sensor, and a transparent glass or plastic rod. The index of reflection at the tip of the rod changes when it is immersed in water, decreasing the amount of light internally reflected (most of it escapes into the water) from the emitter to the detector.

 

[jamesjohnson]

A bit of clarification would be helpful, when you say "The sensitivity setting is to do with the application"...

But if it's simply determining tank fluid level in different settings, I've had good luck using pressure sensors mounted in the plumbing near the bottom or below the tank. These are very sensitive and more reliable than mechanical or electrical solutions that are in contact with the fluid or resultant humidity. Plus they give a constant linear readout of the level, unlike a single mechanical or electrical switch sensor.

For example, I've used the Honeywell 26pc series ( http://www.digikey.com/catalog/en/partgroup/26pc-series/23737). Also, the ASDX series is good (http://sensing.honeywell.com/honeyw...essure-sensors-product sheet-008090-12-en.pdf). These let me know, for example, the water level in a 5000-gallon tank down to a few gallons or so. And they're sealed so I've had zero failures in 9 years of operation. Other methods are more problematic.