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Monday, December 8, 2014

Making 4 to 20mA generator using Potensiometer

AMPLI         CATUR      PLC     TV/AV    ELEKTRO    GITAR
INSTRUMENTASI  KOMPUTER    MUSIK   SOFTWARE

Now i share to you how make a simple ( very very simple ) current industrial generator ( between 4mA to 20 mA ) using a potensiometer for variable current generator, 2 trimmer potensio as span and zero adjust, and 2 cheap transistor as Darlington amplifier. The output of this unit is common ground, so it was not dangerous for any applicatonal instrumen, for example: you try to test the P to I Converter, an Inverter that need the 4-20mA input or anything else.
   Here it is
Pot to Current Converter

Bad Image? Click Here if you need enlargement.
The unit are need 24 Volt DC for supply but 20VDC can do so. ZD1 working to voltage limitation for 18VDC only for circuit.
Transistor BD 140 can do drive for resistance between 50 Ohm to 700 Ohm load ( or 3 x 250 Ohm ) resistively input like a display unit, PLC analog input module, and Controller.
C1 220uF/35V for Filter DC .
Because the circuit and potensio distance was within 2 metres, it be better to use 3x0,75mm NYAF cable but it still good if the distance are more than 10 metres.

The right side of this page is a image that consist of the Pot to Current converter using.


A circle mean status monitor of Forced Draft Fan Damper Percentage and Induced Draft Damper percentage,
B circle mean status monitor of Controll Valve Water to Boiler Water Drum,
C circle mean the Potensiometer to drive the Damper and control valve.

This is a image of Back Up Panel of Maxitherm Boiler of  PG Krebet Baru II Malang that operate as long as Mill periode 2013. Until now the panel was still use to drive the Boiler Machine. The default PLC of the Boiler is Problem and we are could not repair it.

Potensio to controll Main Valve, IDF Damper and FDF damper

 The unit is so cheap and ( may be ) realiable. You can try this at your factory or in the mini lab.
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AMPLI         CATUR      PLC     TV/AV    ELEKTRO    GITAR
INSTRUMENTASI  KOMPUTER    MUSIK   SOFTWARE

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