Q1: Consider part of a control loop, which excludes the transmitter, consisti

Q1: Consider part of a control loop, which excludes the
transmitter, consisting of a process, a controller and a
control valve which may be represented by two dead times of
0.5 min each and three exponential lags of 0.8 min., 1.0
min. and 1.5 min. respectively.

We wish to express this system as an overall first order
plus dead time (FOPLD) model ie gain, time constant and
process dead time. (We will see later that this is often
done, to simplify controller tuning). For this exercise,
gain is considered to be 1.0.

(A) If the transmitter is a flow transmitter whose
behaviour can be described by a dead time of 0.2 min. and
an exponential lag of 0.5 min. in terms of the overall dead
time and overall first order lag how can the system
behaviour be approximated ?

Overall dead time =
Overall time constant =

(B) If the transmitter is a temperature transmitter with a
temperature sensor in a protecting well whose behaviour can
be described by a dead time of 0.7 min. and an exponential
lag of 15 min. how can the overall system behaviour be
approximated now?

Overall dead time =
Overall time constant =

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