Current Meter

[Squibcakes]

Wow, those Allegro Hall Sensors look really good. I have order a couple to test them out.

As for measuring the HV supply, I've only ever used a HV probe connected to a DVM. Sorry, no other idea how to do that.

Cheers

[Charles Linquis]

I have used the Allegro Hall-effect sensors extensively. Bi-directional, great isolation. Good accuracy.

[TK5EP]

Hi all,

I looked the datasheet of the ACS704 which is the smallest device by Allegro (+/- 5A) and it shows a 133mV/A sensitivity.
I think it's a bit low for measuring 50 mA max scale....

An application note for the MAX4172 in a amplified high voltage sensor gives 10mV/mA, which seems to be more adequate, but unfortunately it's not bidirectionnal !

Other possibility is to use an amplified Hall effect sensor, but it needs an ground insolated low voltage supply on the sensor side, which is another problem !

Still looking for the right solution....

[Acetronics2]

Hi, TK5

The best for that voltage levels ( !!! ) is to use a little shunt, an AOP and a V/F converter, then drive an opto-isolator or better an opto-fiber coupler ... remember only CNY21 like HV optocouplers are safe, here ...

on the other side Freq = Current, so it's easy for a PIC to display that !!!

Alain

[TK5EP]

Hi Alain,

Maybe.... but the name problem is to insulate all the circuit from the high voltage side. The OPamp has to be supplied on this HV side, so you need low voltage supply which MUST be HV insulated.

Maybe the Alegro can be adequate if its output is amplified to a level that can be handled by the PIC?

Corsican greetings ...

Hi, TK5

The best for that voltage levels ( !!! ) is to use a little shunt, an AOP and a V/F converter, then drive an opto-isolator or better an opto-fiber coupler ... remember only CNY21 like HV optocouplers are safe, here ...

on the other side Freq = Current, so it's easy for a PIC to display that !!!

Alain

[sougata]

Hi there,

Sorry to catch this thread late. I manufacture series of PIC controlled thyristor based battery charger. For low cost designs I use a piece of wire acting as a shunt in the negative line and then a LM358 for the amplification. It is safe to use it in a HV line also as long as it is referenced to ground. You can use a programmable gain IA like AD620 for your differential measurement needs and couple it to a linear optocoupler like the Vishay IL300. This gives far accurate results than the V/F approach and is cheaper. The only problem is you need another supply. Consider using the IRF PVI series of optos to make a 5ma supply isolated DC-DC converter as well as linear output opto. Maxim has got a very good appnote on high side current measurement (1KV).

Whew! Enough gyans...

If you could post a specific issue with detailed electrical parameter then I might find something on my Hard drive.

BTW I always use a PIC with 10bits res. If thats enough then go on.

Regards

Sougata

[TK5EP]

Hi Sougata,

Thanks for the ideas, my wish is to use no different supply on the HV side to supply the amplifier.
I attached a GIF with the principle of the supply. You see that the supplies are not referenced to ground but to cathode of the tube.
For the 350 V, i could make my measure on the grounded side of the supply, current can flow in both directions with max 50 mA.
The 3500V HV will draw about 800-900 mA.
The 36V only a few mA.

Greetings,

Hi there,

Sorry to catch this thread late. I manufacture series of PIC controlled thyristor based battery charger. For low cost designs I use a piece of wire acting as a shunt in the negative line and then a LM358 for the amplification. It is safe to use it in a HV line also as long as it is referenced to ground. You can use a programmable gain IA like AD620 for your differential measurement needs and couple it to a linear optocoupler like the Vishay IL300. This gives far accurate results than the V/F approach and is cheaper. The only problem is you need another supply. Consider using the IRF PVI series of optos to make a 5ma supply isolated DC-DC converter as well as linear output opto. Maxim has got a very good appnote on high side current measurement (1KV).

Whew! Enough gyans...

If you could post a specific issue with detailed electrical parameter then I might find something on my Hard drive.

BTW I always use a PIC with 10bits res. If thats enough then go on.

Regards

Sougata