Answer / ecxlsync

* Manipulated variable is the one being manipulated by the
final element(usually control valve) to correct the error.
* Controlled variable is the one being controlled or the
desired process value according to the SP.
* Measured Variable is the output of the measuring device.
example water temperature control:
there is a heat exchanger. the are 2 inlets of this exchanger
which is hot and cold water. the hot water must be cool down
when it leaves the exchanger at a certain temperature being
defined by the SP. a control valve installed at the cold
water inlet line to control the flow of cold water. the cold water flow at the control valve downstream is the MANIPULATED VARIABLE. the temp of hot water discharge from exchanger which has attained the setpoint value is the CONTROLLED VARIABLE.

Answer / shasha

a manipulated variable is the one you change to see what
happens to the "responding" variable

a "responding variable is the one that changes in response
to your changing the manipulated variable


The controlled variable(s) is (are) the one(s) that you hold
constant and don't allow to change


For example: Let's say you're doing an experiment to find
out if drinking lots of Kool-Aid makes you stronger. You
take two groups of people, and you feed them exactly the
same things, EXCEPT that Group A gets lots of Kool-Aid and
Group B gets lots of water.

Manipulated variable: Kool-Aid. One group drinks lots, the
other drinks none.

Responding variable: How strong the person is. One group
will demonstrate that they can (maybe) lift some amount of
weight. Can the other group lift that, too?

Controlled variable: All other aspects of the diet, e.g. how
much they're eating, what kinds of food they eat, how much
candy. These are all kept identical between the groups.
• 10 months ago

Answer / ahmed helmy

- Manipulated variable is the output of controller to final control element to correct the error sometimes called also output

- Set point is the desired value for the process

- Controlled variable is the process variable which is the output of the process and measured by the transmitter

- Measured variable is also the controlled variable

- process variable = controlled variable = measured variable

Answer / a

PROCESS VARIABLE - Sensor O/P value in the form of 4-20ma
corresponds to Actual value after conditioning.(say level)

Example: Radar Lvl TX

SET VALUE - Required Process value to make the system
stable.

Example: Actual Tank lvl 100%
Required Lvl (to be maintain) 70%

MANIPULATED VARIABLE - Output Signal(4-20ma) required to
maintain the process variable near to setpoint.

Example: Control valve action to fill the tank.

Answer / ram

The variables that are manipulated to have control over the process variable is called "manipulated variable"
Eg. Level is maintained by closing or opening the control valve ; here control valve position is "mv"

According to this example , both PV and CV ....is the level of the water in tank

Answer / sreenivasan

let e---error,r--setpoint(reference),b--feedback(measured
variable), m---manipulated variable, c---controlled variable

Now

1)e=r-b
2)c=(Control action*e) + Bias
3)m= c(after final control action)

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