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Re: [Amps] RE : Led display problem

To: "Carcia, Francis A HS" <francis.carcia@hs.utc.com>
Subject: Re: [Amps] RE : Led display problem
From: Patrick EGLOFF <pegloff@gmail.com>
Date: Sat, 23 Apr 2005 08:53:56 +0200
List-post: <mailto:amps@contesting.com>
Hi All,

Thanks for all answers to my request. Nice feedbacks ! I think i found a 
nice "hamspiritic" list.

Abt the utility of bargraphs compared to analog meters, i think that 
after initial test during construction, they are better.
In the battle field, you don't need to measure with a high precision but 
only "tune for maximum smoke" ! I don't care to measure my HV or current 
with a high precision, they are always varying !
With LEDs you have no inertia and can easily measure peaks. It's far 
better to put more protections to take care of the tube and operator.
Another good reason is that i broke several meters during 
transportations... :-(
At last, it's a nice brainstorming ...
But, that's only my opinion.

Technicaly spoken :
Well, it seems that there is no simple solution to my problem. The 
easiest is the solution produced by Allegro inc.
http://www.allegromicro.com

They produce very nice hall current sensors, but only for high currents. 
The smallest one has +/- 5A range with a 800V isolation. All in one 
small chip !
The problem is that it has a 133 mV/A sensitivity...
So, i have to switch to a 4CX100000 at least !

The nearest usable solution is to use a IL300 opto coupler that has a 
very linear transfer by using a feedback control. But this solution 
request at least one OP amp on the "hot" side. The "cold" side is 
isolated at 5300 V max for 1 s.
Better than having all the display board with a HV rail but still not 
perfect !

I continue to look for a hall effect sensor that has more sensitivity. 
Several companies are producing hall detectors, but you have to build 
you own core.
Anyone has a solution to build a current sensor as suggested by Mark 
Moss on this list ??

73, and thanks again.
Patrick TK5EP
http://tk5ep.free.fr


Carcia, Francis A HS a écrit :
> Hall effect is an active current transformer device so it would be used to
> measure current.
> I think digi key sells them. It converts current to volts. The device fits
> over an insulated wire for high voltage isolation. It will measure DC
> current unlike a current transformer that only measures AC current. A simple
> panel mounted DVM could be scaled to measure current and be isolated from
> high voltage. gfz 
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