Analogue - To - Digital converter ; Pressure

[unknown_figure]

Hello, lads.


I am looking for ADC circuit which the varying factor is pressure. I would really appreciate any help offered. If you need more details please don't hesitate to post in this thread. I have done some google search on this but haven't found anything that looks like what I am looking or at least reliable.


Thanks

 

[jose9186]

what are you trying to measure, I know is preasure but from where?

 

[unknown_figure]

It's project I am trying to build.. rough idea so far... it's basically Cylinder Gas Level indicator... The gas cylinder is connected to gas regulator which is then connected to Pressure gauge. From the pressure gauge, I would connect the ADC and then to 7-segment display (which will display from 1-10. 10 being the cylinder is full)

If you have comments on the project as a whole and ways to improve I would of course appreciate as well.

 

[jose9186]

try this link https://www.jameco.com/webapp/wcs/s...alogId=10001&ddkey=http:StoreCatalogDrillDown

 

[user_88]

In the present or existing configuration, does the reading on the pressure gauge give a reasonably linear readout, to indicate the remaining amount of gas within the storage cylinder?
What gas, specifically, are you trying to measure?

 

[Reloadron]

Placing a pressure transducer on the cylinder will tell you the cylinder pressure and that is about it. I doubt cylinder pressure would provide a good indicator of how ful the cylinder is or how much gas actually remains in the cylinder Placing the cylinder beyond when the pressure really begins to drop the cylinder is about empty. If that is what you want just place a pressure transducer upstream of the regulator to measure cylinder pressure.

Next would be to place the cylinder on a load cell type transducer (think scale) and monitor the cylinder weight using a tare to remove empty cylinder weight.

As mentioned by User 88 much of this all depends on the gas type you are measuring?

Ron

 

[user_88]

You might want to investigate flow velocity sensors.
The idea is to have a real-time, instantaneous measurement of the gas velocity.
Next, you integrate the gas velocity sensor output signal ... not certain if digital or analog would work best.
The result is a measurement of the actual volume of gas that has passed through the sensor.

... Just browsing ... found this sensor page for gas velocity measurement ...
http://www.ist-usadivision.com/sensors/flow/#gas

 

[Reloadron]

^^^^^

I like that. Measure the flow and totalize it. If you know what you start with you will always know where you are with respect to empty.

Ron

 

[Boncuk]

Unknown - Go figure

What's the pressure to be measured?

Don't expect members to solve riddles without specifying the pressure you have to handle.

Boncuk

 

[unknown_figure]

In the present or existing configuration, does the reading on the pressure gauge give a reasonably linear readout, to indicate the remaining amount of gas within the storage cylinder?
What gas, specifically, are you trying to measure?

propane

 

[Reloadron]

If it is LPG as in Liquid Propane Gas then weigh it as I suggested earlier. If it is totally gaseous then either a pressure transducer or flow transducer and totalize the gas used subtracting from total gas.

Ron

 

[user_88]

Referring to a thermodynamic property chart for propane *....
There would be a constant gas pressure within the propane tank of approximately 140 psia ... at 80°F.
This pressure would remain more or less constant, as long as there was any liquid propane in the tank ... whether the liquid level was nominally full or empty, or any level in between.
The tank pressure would vary more so with ambient temperature than it would with the actual volume of liquid propane in the tank.

If you have a domestic sized propane tank, such as used in some rural areas for heating and cooking, you would have to place the tank on top of a scale sized to weigh several hundred pounds.

* see for example p. 8 of this document:
http://www.osti.gov/energycitations/servlets/purl/893587-D07QAB/893587.pdf

 

[alec_t]

Whether it's in liquid or gaseous form, weighing container plus content is the best solution IMHO. Measuring pressure after the regulator is pointless, as a regulator is designed to maintain the pressure (more or less) constant.

 

[user_88]

Whether it's in liquid or gaseous form, weighing container plus content is the best solution IMHO. Measuring pressure after the regulator is pointless, as a regulator is designed to maintain the pressure (more or less) constant.

... For a portable propane container, weighing the entire unit might be an option.
However, for stationary propane tanks, such as the large household supply types used on many farms, this would not be practical.
A container of this type might exceed a total weight of 1000 lbs.

 

[Reloadron]

Large Tank:

Pour about four cups of water into a small sauce pan or pot.

Place the pot on a stove-top burner.

Bring the water to a full boil. Remove the pan or pot and turn off the burner.

Pour the boiling water onto one side of the propane tank near the base of the neck.

Feel the side of the tank upon which you poured the water. You will find an area where warm meets cool on the side of the tank. When you locate a zone that is much cooler, you have located the propane level within the tank. The propane is unaffected by the heated water.

There done.

Provided as humor but would work. Give or take a little.

Ron

 

[user_88]

The density for vaporized propane at one atmosphere ... 14.7 psia ... is given as about 2 grams per liter, at 32 °F.
A rough estimate for the equivalent volume of 100 lb. of propane, which has been vaporized to atmospheric pressure is approximately 900 cubic feet.

Contact one or two flow sensor manufacturing companies. ... They might let you have a free sample of one of their sensors. If not, maybe they have a demo board, or some other sort of assistance to get a prototype built ...

If you can get a gas flow sensor to produce a signal of reasonable magnitude, you can think about an integration circuit. Try the analog version ... op-amp of some kind ... just to see what kind of obstacles or problems might be involved.