Answer / parag

First of all transmitter is a transducer which convert
input parameter value to 4-20 mA signal that can be send to
long distance like Control room DCS, PLC,...
there are different priciples on which different
transmitter works for measuring either level, flow, or
pressure.
We can use pressure transmitter to measure level and flow.
Differential Pressure transmittter works on capacitance
principle.
Differential pressure transmitter can be used to measure
pressure across any tank, vessel, pump to know the pressure
difference between its upstream and downstream.
Same Differential pressure transmitter can be used to
measure flow if we use across upsteam and downstream of
orifice with square root as flow is directly praportional
to square root of pressure difference across the
restriction.
Even we can use differential pressure transmitter to
measure level as Delta pressure is equal to height of the
tank multiplied by density of the fluid inside.

Answer / selvakumar

1. Differendial pressure method is using in flow TX. Ex:
Q = k * Delta P,Delta p = (p2-p1),K- Constant (we can take
1), Q- Discharge perssure, p2- Inlet Pressure, p1- Outlet
pressure.

2. Level also like same principle, We can use Differential
pressure TX, that is according to the tank model (Closed
tank or open tank).

Answer / narendra mishra

flow Tx->
flow is proportional to sqr root of diffrential pressure.
LEVEL Tx->
level proportional to density x g x hight.
PRESSURE Tx->
depends on type of tx.for exmple in capacitive type
prssre.tx pressure is proportional to distance bw 2 plates

Answer / kathirvan.b

Basically TRANSMITTER is a device which transmits the
signal based on its input signal.There is a difference
between the excitation signal and input signals.The
excitation signal may be air signal(less than or equal to
15 PSI)known as pneumatic transmitter OR electrical signal
(+24V DC or 110 V AC) known as electronic transmitter.Then
the output signal will be 3 to 15 PSI for pneumatic
transmitter and 4 to 20 mA for electronic transmitter.
Then the input given to the transmitters may be of FLOW or
LEVEL or PRESSURE.Based on this input given to
transmitter,it produces a output accordind to process input.
STEP I: [LEVEL MEASUREMENT]
The level sensor may of any type (eg:air purging system)
which measures the leves with the appication of ~20 PSI
inlet pressure,because of back pressure the output air
pressure taken back and given to the transmitter,it
produces 4 to 20 mA or 3 to 15 PSI based on the natuire of
transmitter given to the control room.
STEP II: [PRESSURE MEASUREMENT]
The same procedure for each ,transmitter just measures the
process variables ans produces the output based on the
application of process inputs.

FINALLY TRANSMITTERS ARE SAME BUT THE INPUT,EXCITATION
AND OUTPUT SIGNALS MAY VARIED.

Answer / shakti prada khadanga

transmitter is a signal conditioning element in the loop
itmeans it provides a signal which is standrad and suitable
for controller like DCS or PLC.For example megnetic flow tx
inputs induced mv signal from element(sensor) and gives 4-
20ma output depends upon the range of flow.No a days
transmiitter used are smart tranmitter wich is programed to
convert input signal to standard electrical signl.
Tansmitter type varies depending upon input signal from
sensor.

Thank you

Answer / d k sathish kumar

PRINCIPLE :
IT WORKS ON THE PRINCIPLE OF TRANSMITTERS.

TRANSMITTERS ARE DEVICES THAT RECEIVES INPUTS (PROCESS
PHENOMENA) SUCH AS DIFFERENTIAL PRESSURE, PRESSURE,
TEMPERATURE, ETC.. AND CONVERTS THAT IN TO A REQUIRED OUTPUT
(MAY BE 4-20 MA, MV, ETC..) WHICH IS THEN RECEIVED BY A
CONTROLLER OR INDICATOR.

FOR FLOW & LEVEL - DIFF. PRESSURE IS USED

Answer / ravi vaya

Why flow in squr root ?

Answer / raffi

IT converts the pressure or Differential pressure into 4-
20mA DC and transmit the signal to the PLC

Answer / shan259

Selvakumar,

Always K will not be one.

Answer / satyareddy.b

transmitter converts the pressure or Differential pressure
into 4-20mA,mv DC and transmit the signal to the PLC

i/p converter always for supply pessure from 3~15 psi only !! And from where this converter bleed the air.

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