# Determine the required value of feedback (H) to control the heater output

Homework Statement:
Determine the required value of feedback (H) to stabilize this heater output
Relevant Equations:
θo= θD*P*He / -θD+T*H
Just need a bit of guidance to make sure that I am heading the right way.

Question is:
Fig 3 shows the block diagram of the control of an electric heating
system. The heater is driven from a voltage-controlled power supply, the
voltage V1 being derived from a potientiometer. The output temperature,
θO, is subject to disturbances, θD, because of changes in the ambient
temperature. It is proposed to apply 'disturbance feedback control' to the
system by the inclusion of a transducer that measures the external
temperature and feeds a signal back to the input via a proportional
controller of gain H.
Determine the required value of H to eliminate the effect of the disturbance.

I have attached the block diagram to this post

So far I have

θo= θD*P*He / -θD+T*H

θD = Distubance
P = Power Supply = 2
He= Heater = 0.4
T = Transducer = 0.05
H = Proportional control = ???

But does θD then cancel out as there is a positive and negative on both sides?

This would then give:

θo= P*He / T*H

Is this the correct way to be going as the next step for this equation would be to make H the subject to equal a value?

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collinsmark
Homework Helper
Gold Member
Problem Statement: Determine the required value of feedback (H) to stabilize this heater output
Relevant Equations: θo= θD*P*He / -θD+T*H

Just need a bit of guidance to make sure that I am heading the right way.

Question is:
Fig 3 shows the block diagram of the control of an electric heating
system. The heater is driven from a voltage-controlled power supply, the
voltage V1 being derived from a potientiometer. The output temperature,
θO, is subject to disturbances, θD, because of changes in the ambient
temperature. It is proposed to apply 'disturbance feedback control' to the
system by the inclusion of a transducer that measures the external
temperature and feeds a signal back to the input via a proportional
controller of gain H.
Determine the required value of H to eliminate the effect of the disturbance.

I have attached the block diagram to this post

So far I have

θo= θD*P*He / -θD+T*H

θD = Distubance
P = Power Supply = 2
He= Heater = 0.4
T = Transducer = 0.05
H = Proportional control = ???

But does θD then cancel out as there is a positive and negative on both sides?

This would then give:

θo= P*He / T*H

Is this the correct way to be going as the next step for this equation would be to make H the subject to equal a value?

I don't think that's quite right.

Put units on your figures. For example, don't just say that
"P = Power Supply = 2."