Specific Gravity

[bearwolfe]

Excuse my ignorance I am very new to electronics. Is there a relatively easy way to detect the specific gravity of a liquid through an electronic circuit?

TIA

 

[Vizier87]

a pressure sensor should give the weight of the liquid... and the volume/level of the liquid can be detected using ultrasonic range detection or other means.. these two parameters should be enough to be processed, I think? The two outputs from both sensors can be operated since density: mass/liquid so the values can be processed using a PIC/Dsp. That is if you want to build it from scratch..

 

[bearwolfe]

Interesting, I hadn't thought of it in that manner. I would like to build it from scratch....I am thinking about how to use it in a dynamic environment I would need to take a sample of the liquid in an automated manner, within a system and the use a pressure sensor maybe....I dunno..

 

[MikeMl]

I am not convinced you can determine Specific Gravity from the just the weight/height of a column of liquid, using a pressure sensor and the depth of the fluid. Read the Wiki for some of the complexities.

 

[atferrari]

The volume (implied by the height) is what plays into the calculation of S Gr.

Keep in mind that smaller volumes makes for bigger errors on account of the tolerance of the sensors used. One of the basic things when you measure something.

 

[Vizier87]

if there is a vat and you want to dip in a contraption that tells the density accurately.. then I suppose a small cup with a pressure sensor at the bottom will be adequate, eh? since the volume is constant with any type of liquid brimming in the cup.

 

[bearwolfe]

All true, but for these to operate reasonably accurate in a dynamic (in an operating system) environment may prove very difficult. SG is not mandatory, just seemed like the best way to identify the different liquids or mixtures of liquids in my project.....

 

[MikeMl]

Can you use conductivity to infer the liquid?

 

[bearwolfe]

I don't know....it would make sense that I could if I could find the specific conductivities of the fluids in use and at all temperatures.....not sure as to the accuracy of that method. Again, I am a newbie and do not know the abilities of sensors....

 

[crutschow]

If you run the liquid through a container of known volume and weight with very flexible connections (to avoid affecting the weight measurement), and weighed the container electronically (strain-gauge scale for example), then you could calculate the weight of the liquid and therefore it's specific gravity on a continuous basis.

Edit: If you wanted to rapidly measure the liquid as it changed then you could run it through a coil of pipe of known or measured volume, and measure its weight

 

[Vizier87]

any of the electrical properties of the liquid or a combination of it might also make the medium identifiable. Properties like capacitance, resistance and inductance should differ for different liquids, I think.

 

[Mikebits]

pH might be a good indicator.

 

[Vizier87]

what kind of liquids are we dealing with? ANY type?

 

[bearwolfe]

mineral based fluids - fuels and oils mostly - I need an accurate way of identifying them from each as they move throughout a system either in a tank or in a line, either low/no pressure or under pressure, anywhere in the system really....I was working with a float type system but that proved very irregular and electronically would make it so much easier....if I can find the right way

 

[KMoffett]

I did a quick Google for: electronic specific gravity sensor
And got this: https://www.princoinstruments.com/Densitrol-9-04.pdf
GlobalSpec lists 144 companies that made "Density and Specific Gravity Instruments" (you have register to get in)

Ken

 

[bearwolfe]

That looks awesome, I wonder what the electronics behind it is.....