we can calibrate the control valve by using source meter
which is used to give 4 to 20 ma source to I/P , if any
error in the I/P ,we can adjust the zero or span of I/P.if
any error in the valve position ,adjust the zero or span in
the posisner of the control valve.
If the signal is directly connected to EP then we can use
source meter and adjusting the zero and span by giving 4
and 20 mA. If there is I/P then also this method is
applicable. Now if the pneumatic signal to the positioner
is in standard form and not working properly then we can
adjust the valve positioner for proper working..
The calibrate the control valve used for mA Source
Meter .mA Souce apply for I/P Converter so Opening Closed
for Control Valve .At the opening closed time measured for
position note.Supposed opening for Valve positioner 50% ma
13.5 So adjust the Zero or Span Calibration to Control the
% Actual Value Error Zero/Span
0 4.7mA 0.7 4mA
25 8.5mA 0.5 8mA
50 12.0mA 0.0 12mA
75 16.4mA 0.4 16mA
100 20.5mA 0.5 20mA
It is simply by using a source meter or loop calibrator.
Inject 4-20mA to the current-pneumatic converter and check
the response of the valve. If you notice that an error
occurs,you can adjust zero or span at the control
For the calibration of a control valve a loop calibrator or
a pressure calibrator can be used between 3-15psi.Check the
valve position for 3psi which is to be 0 for a NC type
valves.In such manner check the valve positon for various
ranges(6psi,9psi,12psi & 15psi).the valve positon shoul be
0 for 3psi and 50% for 9 psi and completely opened for
The same procedure is applicable for NO type valves.The
valve is open for 3 psi and completely closed for 15psi.
Any errors occured may be rectified by Zero span adjustment.
Foe selecting control valve if i have the min,normal & max
data of flow rate,inlet pressure& outlet pressure,inlet
tem.&density than how can i assure that these data are
correct,pl. let me know if therew there is any method to
check it.& also how we assure that the Cv we get from this
data is suitable for valve for controlling require flow.
On LPG sphere tank we used LIT for level indication.High
side port is connected to the bottom of the tank while low
side port connected to the top. I would like to know how to
fill the glycerin on its low side with two condensing pot
installed,one from top and the other one for its drain
line.Please I need your expertise...thanks
Anybody know how to create a ladder programme for power
switch in TV remote without using counter... ie TV can be
turn on and turn off using single push button switch... on
pressing the switch first time TV turn on and hold the on
state till i press the switch again, and after TV turn off.
If a differential pressure transmitter is calibrated for
0~2500 mmH2o and transmits a 4~20mA dc signal. The
transmitter is placed across an orifice plate which is sized
to create 2500 mmH2o differential at 5000m3/Hr
a) what is the flow rate when the transmitter signal is
b) what is the signal output of the transmitter when flow
rate is 2500 m3/Hr ?