This document summarizes a differential pressure transmitter. It discusses that a differential pressure transmitter senses the difference in pressure between two ports and produces an output signal proportional to the calibrated pressure range. It then describes the construction of an industrial differential pressure transmitter, which has two housings, with the pressure sensing element in the bottom half and electronics in the top half. It also outlines the internal arrangement of the transmitter including the direct pressure sensing element, signal conditioning electronics, and 2-wire 4-20mA current output. Finally, some common uses and the advantages and disadvantages of differential pressure transmitters are listed.

1.  DEPARTMENT :-
CHEMICAL ENGINEERING
 BY :-
 Krishna Kant
Nayak
 MNIT, Jaipur
 2016uch1239

2.  CONTENTS :-
I. Differential Pressure
II. Pressure Transmitter
III. Definition
IV. Industrial dp transmitter
V. Construction
VI. Internal arrangement
VII. Uses
VIII. Advantage and disadvantage

3.  The difference in magnitude between some
pressure value and some reference pressure . In
a sense , absolute pressure could be considered
as a differential pressure with total vacuum or
zero absolute as the reference .Likewise ,
gauge pressure could be considered as
Differential Pressure with atmospheric
pressure as reference.

4.  A Pressure Transmitter is used where
indication and/or record of pressure is
required at a location not adjacent to the
primary element.
 A Pressure Transmitter is used for both
indication and control of a process.
 A Pressure Transmitter is used where overall
high performance is mandatory.
 These can be either Gauge , Absolute or
Differential Pressure Transmitters.

5.  Differential pressure
transmitter is a
equipment which
sense the difference in
pressure between two
ports and produce an
output signal with
reference to a
calibrated pressure
range.

6. INDUSTRIAL DP
TRANSMITTER
 The industrial differential
pressure transmitters are
made of two housings.
 Pressure sensing element is
housed in the bottom half,
and the electronics are
housed at the top half.
 It will have two pressure
ports marked as “High” and
“Low”.

7. A. Direct Pressure sensing element (located in
the lower housing):-
 This diaphragm is a mechanical device.
 It is placed in between the two pressure inlet
ports.
 The diaphragm will be deflected by the applied
pressure.

8.  The electrical signal generated at the lower
chamber by the sensor is in the range of milli-
volt only.
 This part is housed on the upper part of
transmitter.
C. 2-Wire 4-20mA Current Transmitter:-
 A DC output current is generated which is
directly proportional to the pressure range of
the Differential Pressure Transmitter.

10.  SOME USES OF DP TRANSMITTERS:-
A. Measuring positive gauge pressure
B. Measuring absolute pressure
C. Measuring vacuum
D. Measuring liquid level
E. Measuring gas and liquid flow

11. ADVANTAGE DISADVANTAGE
 Easy to install/remove.
 Offer very little pressure drop of
which 60% to 65% is recovered.
 Meter can be easily maintained.
 Measures a wide range of flow
rates.
 They have a simple
construction.
 They have easily fitted between
flanges.
 They are most suitable for most
gases and liquids.
 They are inexpensive.
 Requires homogeneous fluid.
 Requires single phase liquid.
 Requires axial velocity vector
flow.
 Causes a pressure drop in fluid.
 Fluid viscosity limits measuring
range.
 Requires straight pipe runs to
ensure accuracy is maintained.
 Pipe line must be fully
especially for liquid flow
measurement.
 They have low range-ability.

12.  Wikipedia
 NPTEL Website