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General Science for RRB JE, NTPC Exam : Part 42 (in Hindi)
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Hemant Mishra
Cleared RRB Clerk , SBI Clerk pre, NTPC 2016, 1 year experience in software developing along with 5 year Experience in Teaching .

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(3)
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Unacademy user
AK
At time 13: 34, in order to choose a controller, Suppose temperature transmitter reads temperature below set point, in that case also the positive error to controller increases, In this case, we need to reduce the flow of water, so air pressure to the valve should increase. So for the controller, increasing error to controller causing an increase in signal to increase air pressure which in turn, due to indirect action valve reduces the flow of water. So, it says that the controller should be a direct acting controller. Please explain why such a dfference is arising between negative error (as you have explained) and positive error taken as example.
Vidhi Shah
a year ago
for controller to be direct acting or indirect acting, another factor to consider is in case of plant failure, what will be it's action. as we are discussing Colling water here, we would want that at 0 signal we should have 100% flow of cooling water
AK
Amaresh Kumar
a year ago
Please clarify the doubt arised. According to the case taken by you, controller comes out to be indirect acting whereas for the case I've taken, controller controller comes out to be direct acting for the same problem.
Vidhi Shah
a year ago
the issue is that u are classifying error as positive and negative...if u look at 09.45 of video u will get ur answer. It's about error magnitude with which you decide controller action. and action of valve needs to be fixed before fixing other things.
AK
Amaresh Kumar
a year ago
Did you mean to say controller cannot differentiate between positive error and negative error and behaves in same way in both cases ?
Vidhi Shah
a year ago
a controller is programmed by a human...it will think what you program it to think!
sir This is Nose radius in case of single point cutting tool....nose is the tip of tool which has a curvature and its radius is measured in "inch" according to American standards association....but in this question all options have unit of angles...and only one option has unit of distance...so simply can choose mm.