DP Transmitter Calibration
DP Transmitter Calibration
DP Transmitter Calibration
After completing all the preliminary requirements, you can proceed in the following
ways:
● Calibrate the 0%, Lower Range Value (LRV) of the transmitter to the LRV of the
calibration range. Calibrate the transmitters span to 100%, Upper Range Value
(URV) of the calibration range. For example: If you are using a DP transmitter with
power output 4-20mA to measure pressure in the range 0-300 PSIG, then the
transmitter’s 0% LRV is 4mA, and is calibrated to 0PSIG. Similarly, the 100% URV
is 20mA, and will be calibrated to 20 mA.
● Locate the ZERO and SPAN/RANGE screws of the transmitter by referring the
instruction manual. These screws are each connected to the potentiometer and
can be turned easily.
The potentiometer allows up to 20 turns between the maximum and minimum
resistance. This means 20 clockwise or anticlockwise turns of ZERO and SPAN
screw will cause the potentiometer to be at maximum or minimum. In many
brands of DP transmitters, the ZERO and RANGE adjustments are
interconnected. This means adjusting one screw may affect the other.
● Turn the RANGE and ZERO screws clockwise 20 times. Next, turn the screws 10
times in the counterclockwise direction to adjust the potentiometer between the
maximum and minimum resistance. This step is performed to set the mid
resistance point at 50%.
● Apply the LRV 0% on the high side of the transmitter, and low vented side. This
helps diminish the differential pressure across the DP cell of the transmitter.
● Adjust the ZERO screw on the transmitter by observing the 4mA indication in the
current meter. This is the LRV output of your transmitter. At times, this value may
not be 4 mA, but you should get a value closer to that.
● Next, apply pressure on the high side of the transmitter to increase the value to
the 100% higher value (URV) of the calibration range.
● Adjust the RANGE Screw by observing the meter’s current indication, which
should show 20 mA, which is the 100% URV output of the transmitter.
● In an ideal situation, 100% of the transmitter's input should correspond to the set
standard readings of transmitters 100% output (4-20 mA). Accurately calibrated
pressure is the one, where the values of input equals to the output for all values
between 0-100percent.