Low Moisture Content Tester - Help Wanted

[stay alive]

Hi, this is my first post on the exellent forum.

I am wanting to build a low moisture content tester which is to be used for testing the general condition of brake fluid in cars.

My research to-date has told me that anything over 4% moisture content, as tested in the reservior, will require a fluid change. 0 - 2% is OK and 2 - 4% is border line thus requiring a change in the next three to six months.

I have seen a circuit that came from a Maplin magazine which read from 20 - 100% which of course is no good but the principle was there, I guess.

Can anyone suggest anything simple that I can work with?

Regards
Paul

 

[Nigel Goodwin]

I imagine the Maplin design just measured it's resistance?, it's likely that low percentages are too high to measure with any reliability?. If you have a meter with a good high resistance range I suggest you try measuring samples with differing degrees of water added.

Note that you will require the probes to be the same distance apart, and inserted the same depth, to give useful comparisons.

 

[mechie]

Water detection

A couple of questions...

Is this intended to be an 'on-line' measurement - probe in reservoir all the time
OR
An occasional test (possibly pulling a syringe full from the reservoir - allowing some fancy destructive testing... ??? )

How do you define the percentage ? by volume? weight?

 

[stay alive]

I am planning a probe type tester which is to be plunged into the fluid in the reservoir.

The figures I quoted are the percentage volume of water in the brake fluid.

Apparently the hygroscopic nature of the fluid means that it naturally absorbs moisture from the air and therefore over a period of time it reaches such a level (over 4%) whereby it requires replacing.

Thanks

 

[audioguru]

Hi Mechie,
I made a plant soil moisture amount project that measures the soil's resistance using AC to avoid probe corrosion and unplating. It measures from about 47 ohms to about 56K ohms:
https://www.electronics-lab.com/projects/science/018/index.html

I tested it for a chemist to see if it would work for his application. I found that distilled water, like the condensed moisture in your brake fluid, doesn't have resistance unless there is free ions from salts in it!
Even my tapwater that is filtered with activated carbon measures a very low resistance. It tastes fairly pure.

Mechanics have told me to dispose of brake fluid that has been in contact with air because it is contaminated with condensation. You don't want it to boil when braking hard! :lol: