Why 1-5 vdc a standard?
1-5Vdc is not a standard, it is a widely used convention for 4-20mA current loops.
A 250 ohm resistor drops a 1-5 Vdc voltage proportional to the 4-20mA current.
DCS analog inputs historically used 250 ohms for 4-20mA analog input resistance and over time that value has become quite common.
But I have seen 1 ohm, 4.7 ohms, 10 ohms, 12 ohms, 24.9 ohms, 50 ohms, 62.5 ohms, and 100 ohm resistances for 4-20mA current input.
Is This Answer Correct ? | 13 Yes | 2 No |
tell me about Woodward505 Function as a point of Instrument Engineer.
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 =
What is loop or pigtail in an impulse line?
8 Answers Qatar Airlines, Qatar Petroleums,
please send the hpcl (instrumentation) model placement papers to my mail....
9 Answers HPCL, Invensys, IOCL, ONGC,
where the use of direct action control valve?
what does 5/2 solinoid valve means?
Define cryogenic?
protection relay watchdog contact operation?
which type inter lock use in petrochemical refinery,and oil & gas?
An atmospheric storage tank has a diameter of 20 m and a height of 8m.It is half-full of liquid with the remainder of the space containing air normally at atmospheric pressure. If the connection to atmosphere is accidentally closed off and 10 cubic m of liquid removed, what happens to the internal pressure of the tank? What are the possible consequences for the tank?
What is two wire system and how it work
What is a flow meter?