How do you calibrate a D.P. transmitter?

The following steps are to be taken which calibrating:

1. Adjust zero of the Tx'r.
2. Static pressure test : Give equal pressure on both sides of the transmitter. Zero should not shift. If it is shifting carry out static alignment.
3. Vacuum test : Apply equal vacuum to both the sides. The zero should not shift.
4. Calibration Procedure: 
   1. Give 20 psi air or 24V dc supply to the transmitter.
   2. Vent the L.P. side to atmosphere.
   3. Connect output of the Instrument to a standard test gauge ot Multimeter and adjust zero.
   4. Apply required pressure to high pressure side of the transmitter and adjust the span.
   5. Adjust zero again if necessary.