Thursday, 31 July 2014

PlC OR DCS Analog Input block for 4-20ma, 1-5V input ,Hart 4-20ma Input

1) Current 4-20ma input from field sensor amplifier. 4-20ma current is converted to 1-5v using 250 ohms load resistor on interfacing board.
2) Current 4-20ma from transmitter given directly to AI module .
3) Current with Hart Signal given to AI module which supports to HART signal. Digital information superimposed on Analog signal.

Galvanic Isolation With Three Types Optical,Inductive Or Capacitive Isolation

Galvanic Isolation : Isolation of two grounds. Field ground and system ground isolated from each other.
1) Optical isolation : Hi speed. Require two independent supply for both the sides.
2) Inductive isolation : comparatively slow. Power generation in secondary will be possible.

Wednesday, 30 July 2014

De energized condition of 24v Dc Solenoid Coil monitoring Concept and Block Schematic


Status of solenoid coil monitored continuously during De-energized condition. Very low Constant current injected for detecting open or short condition of Dc solenoid. Window comaparator for checking healthy status of solenoid. Energized condition is overriding condition and ignore action taken by detection circuit during this period. Healthy signal relay gives free potential contact for logical configuration of status.

Universal Analog Input Isolator Module for 4-20mA Input With 2 or 4 Wire Or 1-5v Output Voltage Configurable

Two or Four wire Transmitter : 2 or 4 wires required for operation of Transmitter.Four wire mode transmitter powered externally. 2 wire mode powered from AI module & series connection with load.
  1) 2 wire mode input : +24v dc power given by analog input module and return path is connected to load resistor inside Analog input module.
  2) 4 wire mode input : Transmitter powered externally. 4-20ma current given to current input AI module.
  3) 1-5v mode input : 4-20ma current from transmitter given to load resistor 250 ohms on field Interfacing Module. Output 1-5v given to voltage input AI module.