Answer / carl_ellis

A DC power supply converts it input, AC line voltage to a
regulated DC voltage output.

A relay coil can be driven by one voltage and its contacts
can operate at a different voltage so a relay coil could
operate at 230Vac, with its contacts switching 24Vdc. But
that's not 'converting' AC to DC; the relay itself requires
that those voltages be supplied to it, it can not 'convert'
AC voltage to DC voltage.

There are linear power supplies and switch mode power
supplies (SMPS).

Relay logic is the name for the use system logic consisting
of discrete relays, switches, timers and counters which are
wired point to point.

Ladder logic is the symbolic representation of the same
elements used in relay logic: relay coils for inputs, relay
contacts for outputs, contacts for switches, timers and
counters in PLC programming.

The ladder representation looks like a ladder with rails and
rungs. The rails are line power rails, the rungs have the
logic elements in parallel or series as needed.

Carl Ellis
Measure First

Answer / sajjad khan

in PLC relay use only switching device'
i think using rectification convert 230 AC to 24 VDC
use 105400 volt PF and diodes and filter copacitor 220uf35 volt copacitor and Ziner Diode 24 volt 2 watt.
it's circuite is very simple and small.

what is maximum vaccume?

4 Answers  

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where do you give the 4-20 ma i/p in a MIL control valve?

3 Answers   Siemens,

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why we are using drum level control valve air to close?

0 Answers  

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We have ZR22G-100-S-A-E-T-T--E-A/CV/F1 Model Zirconia Oxygen analyser which is Yokogawa make. I kept the analyser in Flue gas path at Air pre heater area. My plant is 7.5MW Biomass power plant. For a particular fuel, Coconut Husk which contains Sodium and Potassium chlorides iam not getting proper reading, Analyser output always Zero. I calibrated the analyser and it is OK. For Other fuels like Wood chips, Cholam waste, DOB, Groundnutshells, Ply wood waste and all iam getting actual percentage of Oxygen. What is the main reason behind this draw back?

2 Answers  

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What is protocol ?

3 Answers  

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how we can measure the interface level?is it possible to measure interface level with dp or pressure transmitter?

2 Answers  

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Hi buddies! my name is sachin and i am working as a electrical and instrumentation engineer in a paper plant. right now i am facing a problem and if someone could help me it will be an immense pleasure to me. i am using AC 800M to synchronise DCS500 drives on paper machine and rewinder.communication is on PROFIBUS and we are using NPBA-01 module to link profibus to DC drives.But these days two of these drives are showing a error named FIELDBUS COMM.TIMED OUT and the drives get tripped.I have changed the NPBA module and PROFIBUS cable.So if anyone can do please help me out with this problem.I'll be highly grateful.

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Why we used cage in control valve?

8 Answers  

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ON RADAR INTERFACE LEVEL TRANSMITTER IF DI-ELECRIC IS WRONG WITH CONTINIUS PROCESS THAN HOW CAN INDENTIFY OR HOW CAN I PUT NEW DI-ELECTRIC VALUE?(ROSEMOUNT-TDR-3300-COXIAL PROBE TYPE)

1 Answers   Chevron Phillips,

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typical loop drawing of a simple feedback control comprising of one transmitter and one control

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Calculate the maximum pressure drop that can be allowed to occur across a control valve, so that we can prevent cavitation / flashing from occurring. Use the following formula: Δ P allow = Km (P1 – PvapourA) where, Δ P allow - the maximum allowable differential pressure for sizing purposes, or terminal pressure drop; Km- the valve recovery coefficient from the manufacturer’s catalogue; P1 - absolute inlet fluid pressure; PvapourA - absolute fluid vapour pressure at the inlet temperature; Use Atmospheric pressure = 101.3 kPa, P1 = 1200 kPa(g), PvapourA = 4 kPa, KM = 0.72

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what is skin thermocouple?

3 Answers  

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