I have to add a function of liquid level detect to the probe in my
the probe goes downward to search the surface of some polar solutions,
when the probe gets to the level of liquid, the sensor will give me
back some signals about it, while when it goes upward back and leave
the surface, the sensor will also give me back some signals about it.
I think the capacitance type will help me to complete it.
But can anyone please tell a good place to buy this kind of sensor,
which can be used as OEM in my task.
Thank you, very much.
Are you saying the probe moves? Such probes are available but they are not
capacitance based and are not necessary for finding water.
How many media do you have? How many interfaces? At the bottom you have
water. Above that is air, oil, methane, or what? Please describe your
application with more information.
There is quite a variety of commercially available capacitance probes used
for detecting water, oil and air. Try a web search for capacitance level.
Yes, my probe can move up and down to search the liquid.
Simply, there are only two media in my task. One is air above, another
is polar liquid as water at bottom.
The system work as an analogy to a human using his finger to touch
He drops his hand downward to a base of water. When his finger reaches
the surface of the water, he can feel it.
In my work, a probe works as a 'finger', then the 'feeling' comes from
Which kind of sensor can I use?
There are MANY ways of finding the height water in air. You are asking for
information on one particular method that is very expensive and high in
maintenance when there are many alternatives. Is there any particular
reason why you are asking about a moving probe? The only times I have been
involved with servo tracking level sensors is when we were looking for the
height of a sand-like solid submerged within liquid. When I say we need
more information, I mean we need answers to the following questions:
1 - What is the range of level you are looking for? I mean, 0 to 10 mm, 0
to 100 meters? You can see this makes a huge difference in the type of
2 - What is the accuracy you need? Are you looking for +/- 0.01 mm, +/- 20
mm? Again this has very big impact on the selection.
3 - Is the water clean or dirty? Some devices have a high tolerance for
dirt, others cannot tolerate any. Some even require it!
4 - Is the water corrosive?
5 - Are there mechanical disturbances in the water which could interfere
with any inserted device?
6 - Will there be opportunity to withdraw the device for service or is it
important that the vessel never be drained?
7 - Is the environment subject to hazardous vapours such as gasoline vapour?
Once again, this influences your choice.
8 - What is the maximum and minimum ambient temperature the instrument will
be exposed to?
9 - What is the particular reason you are looking for a moving instrument
such as you describe below? If this motion is really necessary, It is
unlikely to be combined with a capacitance probe. If what you are looking
for requires a capacitance probe, they can be purchased up to 10 meters in
Assuming that your application is exactly as you have described it, the
simplest sensor would simply be a wire connected to a simple electronic
circuit to detect conductivity.
I agree with Walter. There is a lot more information you need to look
at in deciding the type of probe you want. If it is just water and
cost is an issue then you could simply uses a float capacitive system,
Check out the Vega instrumentation webiste. They offer alot of
differnet sensors. Vega is just one company that manufactures level
If you answer the questions below then it is easy to suggest a sensor
for yoru application. The only other question I woul add. Is you
vessle under vacuum or positive pressure?
On 10 May 2004 04:28:09 -0700, email@example.com (Yao Dong)
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