Two Wire Pressure Transmitter using Bourdon Tube Pressure Sensor and LVDT - An Advance Pressure Transmitter

Abstract

Bourdon Tube pressure Gauge is a mechanical type pressure transducer. Its display unit is a pointer attached with itself with a rack and pinion arrangement mounted at a spindle. Hence this cannot be used for remote measurement. Hence in order to measure the pressure sitting at the control station, a special measuring technique is to be adopted. The proposed technique, discussed in this paper, uses Linear Variable Differential Transformer (LVDT) and a twowire transmitter and this can be used for reading the pressure of a process remotely. A ferromagnetic plunger type core is attached with the tip of the Bourdon Tube. The core here acts as a secondary sensing element which moves in an electromagnetic field generated by an excitation voltage in the primary of an LVDT. The movement of the ferromagnetic core with the movement of the tip of the Bourdon Tube generates an induced voltage in the secondary of the LVDT. The output of the LVDT is connected with a two-wire pressure transmitter to produce 4-20 milliampear corresponding to the pressure variation. The measurement of the current gives the pressure of the process with a good linearity and repeatability. The necessary theoretical equations along with the experimental results have been reported here clearly.