Calculate Control Valve Stem Position

An electronic  loop controller  outputs  a signal of 8.55 mA to a direct-responding control valve (where 4 mA is shut and 20 mA is wide open).

How far open should the control  valve be at this MV signal level?

Calculate Control Valve Stem Position

We are solving this problem using standard 4-20mA conversion Formula. Click here for formula

To solve for percentage of stem travel (x) at 8.55 milliamps of signal current (y), we may use the linear equation developed previously to predict  current in milliamps (y) from signal value in percent (x):

Therefore, we should expect the valve to be 28.4% open at an applied MV signal of 8.55 milliamps.

We can also solve the problem using direct formula. Click here for formula

Also Read: Instrumentation Formulas