MarkNightingale
Lifetime Supporting Member + Moderator
Hi Guys,
I am trying to get a level reading of a tank using a pressure transmitter, I have nearly got the formula that I wont but I'm struggling to get it into my PLC code.
I am using RSLogix 5000.
The pressure transmitter is 4-20mA range of 0-500mBar.
The tank is 3.8 meters tall and 1.7 meters wide. At full capacity it will hold 23,000 litres of water. There is a conical bottom on the tank which is the bit that I am finding it hard with.
I know that in a linear tank 27.71 inches of water exerts 1 P.S.I on the pressure transmitter.
This means that 0.70 metres = 1 P.S.I
So 0.70 metres = 0.069 Bar = 69mBar.
Therefore 3.8 metres = 374mBar.
So in my PLC code I am scaling the raw analogue input and scaling it between 0 and 500.
I am then taking that value and scaling it again between 0 and 23,000.
Now all this looks fine but when I meter water into the tank the values don't add up, so this is because of the conical bottom. I have scoured the internet, but without much luck so was hoping someone could point me in the right direction.
I have got all the tank dimensions so I am thinking of working back and using the volume of the tank.
Any ideas or suggestions would be grateful.
Thanks
Mark
I am trying to get a level reading of a tank using a pressure transmitter, I have nearly got the formula that I wont but I'm struggling to get it into my PLC code.
I am using RSLogix 5000.
The pressure transmitter is 4-20mA range of 0-500mBar.
The tank is 3.8 meters tall and 1.7 meters wide. At full capacity it will hold 23,000 litres of water. There is a conical bottom on the tank which is the bit that I am finding it hard with.
I know that in a linear tank 27.71 inches of water exerts 1 P.S.I on the pressure transmitter.
This means that 0.70 metres = 1 P.S.I
So 0.70 metres = 0.069 Bar = 69mBar.
Therefore 3.8 metres = 374mBar.
So in my PLC code I am scaling the raw analogue input and scaling it between 0 and 500.
I am then taking that value and scaling it again between 0 and 23,000.
Now all this looks fine but when I meter water into the tank the values don't add up, so this is because of the conical bottom. I have scoured the internet, but without much luck so was hoping someone could point me in the right direction.
I have got all the tank dimensions so I am thinking of working back and using the volume of the tank.
Any ideas or suggestions would be grateful.
Thanks
Mark