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7 comments
Anonymous Poster

4~20mA Current Injector

02/08/2009 11:55 PM

Dear All,

Can we DIY a 4~20mA injector, a 3 steps required, from 4,12 and 20mA.

Thanks

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Participant

Join Date: Oct 2008
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#1

Re: 4~20mA Current Injector

02/09/2009 12:44 AM

give the complete data

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Power-User
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#2

Re: 4~20mA Current Injector

02/09/2009 1:40 AM

Hi there,

Yes you can. You need to build a simple current divider circuit. Try that great encyclopedia google for current divider circuits.

Regards,

Craig

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Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

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#3

Re: 4~20mA Current Injector

02/09/2009 3:55 AM

Yes very simply if you have a even little experience in electronics.
A couple of 9v batteriers and an LM317 (National have great data sheets on it just google LM317 and read the application notes.)
you'll need a few other components.
If yo aren't too worried about accuracy, you could probably just use 2 pp3 batteries in series and a resistor in series for each current.

Del

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Guru
United Kingdom - Member - Olde Member!! Engineering Fields - Instrumentation Engineering - New Member

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#4
In reply to #3

Re: 4~20mA Current Injector

02/09/2009 2:18 PM

At last a reply that addresses the problem!

A GA from me...

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Associate

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#5

Re: 4~20mA Current Injector

02/10/2009 6:50 AM

TRY THIS CIRCUIT.

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Guru
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#6
In reply to #5

Re: 4~20mA Current Injector

02/10/2009 10:44 AM

That circuit will only do 0 to 5 mA....

Using a 7805 the resistors need to be.... 220Ω with a pot of 500Ω in series to cover 4 to 20 mA

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Anonymous Poster
#7
In reply to #6

Re: 4~20mA Current Injector

07/11/2010 6:15 AM

But 220 ohm series with 500 ohm = 720 so minimum current would be 6.94 mA...

so POT. should more than 500k..

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