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Hi friends, from Aug 4th onwards iam getting spikes for
analog inputs in our DCS for a period of 800ms. I throughly
checked every thing, finally i found that the DI, DO's from
MCC panels shields are terminated in the Signal Earth where
Analog Input signals shields are terminated. Is there any
problem with this type of termination?. i checked the
induction voltage from MCC and getting around 25VAC, please
suggest me in this concern. Our plant is 8months old only.
DCS is Siemens Make Simatic PCS7, and the transmitters are
Yokogawa make.
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Answer Posted / sankarithi
Hi Friends only problem is due to earth pit. I throughly
checked every thing, finally i found that the Earth pit
totally became dry. I serviced the pit,Now there is no
spikes.
| Is This Answer Correct ? | 4 Yes | 1 No |
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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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