I need to determine the pressure existing in a liquid in order to calibrate a pressure transducer. Does anyone know which instrument we can use to detect a pressure of a slowly flowing liquid? For example, imagine I am applying a pressure to a liquid through the piston of a syringe and I need to determine the pressure existing inside the barrel of the syringe (in the liquid). I should be able to detect pressure ranging from 2-30 mmHg. If anyone got any clue, please share your knowledge. Just the name of the instrument/instruments enough for me to dig out information.
It appears that you want to calculate gauge pressure in the liquid - ie relative to the surrounding atmospheric pressure (which can vary).
A simple method for calibrating the transducer is to immerse it in a known depth $h$ mm of water. The gauge pressure is then $h/13.56$ mmHg. 13.56 is the relative density of mercury compared with water.
However this does assume that the atmospheric pressure is the same when measuring as it was during calibration, so you will need to apply a correction for any difference. You can measure atmospheric pressure with a manometer.