trying to select materials for a liquid probe
hello, parallax stamps in class forum readers. i am trying to build a circuit inspired by Chapter 5 in the Applied Sensors text. my design involves control of a 5 gallon bucket, but i am concentrating on the measurement aspects specifically right now and i want to be able to gauge water level, temperature, EEC and ph.
so here i am trying to concentrate on one at a time and i'm working on water level. if the sensor is going to include low levels the probe is going to have to be almost a foot and a half, so i'm hanging two steel threaded rods. should i stick with stainless steel? and what gauge wires should i use to connect the probes to the circuit? is it possible to get all these measurements using different circuits connected to the same probes?
so here i am trying to concentrate on one at a time and i'm working on water level. if the sensor is going to include low levels the probe is going to have to be almost a foot and a half, so i'm hanging two steel threaded rods. should i stick with stainless steel? and what gauge wires should i use to connect the probes to the circuit? is it possible to get all these measurements using different circuits connected to the same probes?
Comments
·· You are wise to explore each individual sensor method individually.· This also answers your question though about using one sensor for everything.· That's not going to happen.· The proper probes/sensors for your needs will be somewhat dependant on the contents of the container as well as the environment.· After all, if you're outdoors you'd want sealed sensors.· Is the tank going to be sealed, will the contents slosh, is there pressure, etc?· I would concentrate on one sensor at a time, combining aspects when needed.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
as elements are added to the mix bucket (through automation) i'm planning to program compensation to keep the levels steady. some mix goes to the garden (this is not a scheduled event but based on input) and the level goes down to a trigger point where the program adds the right mix to get the level back up.
the bucket won't be pressurized and (except for a few vents that will allow for air displacement in the bucket) the bucket will be sealed. the level will be changing but it will be upright at all times, so no sloshing. i'm pretty sold on the probe example in the applied sensors text and i'm specifically interested in how i can apply it to a five gallon mix container (standard bucket, you know the type).
thanks for the help,
taylor
With regards to these specific questions:
<<should i stick with stainless steel? and what gauge wires should i use to connect the probes to the circuit? is it possible to get all these measurements using different circuits connected to the same probes?>>
Yes, use stainless steel for the probes. The fertilizer mix will be pretty caustic!
The currents in the wires are small, and the wires should not have to run far (?!), so the gage is not too important. Say, 22 gage. I don't know exactly what you mean by the 3rd question. One probe will not be able to make all of the measurements, and I certainly agree with Chris that it is best to try out one probe at a time and get it working before tackling the whole system. It should be possible to mount all of the probes on one support such as the SS threaded ground rod.
Does that help? Maybe there is more about your planned automation that needs a complete analog level sensor?
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Tracy Allen
www.emesystems.com
thanks again and big up to all the parallax forum readers and moderators!
taylortronic