Level Calculation using 2 transmitters

[jpratik92]

Hello, 

I have two pressure transmitters connected to a tank. One at the top and one at the bottom. How can I calculate the level of the tank ? I know the height and Specific gravity of the materials. 

 

Thank You 
Pratik Jain

[Steve Bailey]

https://blog.wika.us/products/level-products/how-differential-pressure-transmitters-measure-level/#:~:text=A%20differential%20pressure%20transmitter%20calculates,lids%20and%20bottoms%2C%20etc.)

[DanW]

Presumably the reason for two pressure transmitters is that the tank is a closed vessel and there's pressure in the vapor space above the liquid.

If you subtract the vapor pressure measured by the upper transmitter from the pressure measured by the lower transmitter (units have to be the same), convert the pressure value to a distance value (inches/feet,mm/m) and then divide the distance value by the Specific Gravity you will get physical level value.

The problem with using two pressure transmitters instead a single differential pressure (DP) transmitter is that the combined error of both transmitters can be significant.   Convention calls for using a single DP transmitter.