# CNG Level sensor working

1. Jun 8, 2007

### signorvivek

Hey,
As all of u know CNG Level sensor gives an output of level of CNG in the cylinder. Do pressure of CNG in cylinder is caliberated level ?

2. Jun 8, 2007

### Danger

Welcome to PF, Signorvivek. I'm afraid that I'm not entirely sure what your question is. Are you asking if the level is determined by a pressure measurement?
I don't know about the type of installation you're referring to. For 'household' size propane tanks, it goes by either the weight of the tank or the temperature on the outside (it's colder where the liquid is). Other systems have a float mechanism inside the tank that sends a signal to the gauge. I don't know how accurately you could determine the amount of fuel by the pressure alone.

3. Jun 8, 2007

### ank_gl

now i dont know anything about how do you sense the amount of fuel left in the CNG tank(or cylinder), but i guess knowing the pressure and temperature inside the cylinder will let one know the amount(mass i mean) of gas left.

4. Jun 8, 2007

### Q_Goest

The pressure of a container holding a saturated fluid won't tell you anything about quantity. The fluid has to be superheated (ie: in a gas phase) in order for the pressure to correspond to a quantity.

I'd assume you're referring to CNG (CH4) being stored as a compressed, superheated gas, so yes - pressure would correspond to mass, but if you're referring to LNG, which is generally the saturated fluid, then no, the pressure won't correspond to mass.

Note that LNG is just CH4 that's been liquified at roughly -259 F or -162 C, and thus is stored as a cryogenic liquid.

5. Jun 11, 2007

### signorvivek

As u are telling temperature is also a parameter other than pressure for measuring level in the CNG Cylinder....
So i must have a pressure sensor and temperature sensor for measuring Level in cylinder.

6. Jun 11, 2007

### signorvivek

Can you tell me what are the different types of Level sensors available for CNG cylinder?

7. Jun 11, 2007

### Q_Goest

CNG is "compressed natural gas", it is gasseous at ambient temperature. Saying there's a "level" implies a liquid level, so please verify we're talking about a gas.

To measure the total mass of a gas in a container, you need to know the pressure, temperature and volume of the container. You could also measure the mass on a weight scale, but that's very rarely done. I don't know of any other way to measure mass in a cylinder.

8. Feb 25, 2010

Any one can tell me how to measure the temperature of CNG in a cylinder.

9. Feb 25, 2010

### Mech_Engineer

How about with a thermocouple? Measuring temperature is easy compared to some other metrics...

10. Feb 25, 2010