[SOLVED] Question regarding AC current feed back

[goldsmith]

Dear All
Hi
Thank you for your attention .
I want take sample from an AC current that it's frequency has variation from 0.1 HZ up to 2KHZ . my maximum current is around 10 amperes , and i need precision around 5ma . ( i want consider temperature effect on this process and decrease it's effect as much as possible .)
Is possible that you guide me , please ?
Thanks in advance
Goldsmith

 

[FvM]

Why not DC feedback? Using a current transformer as sensor would be the only serious reason against it, hardly to achieve for 0.1 Hz however.

 

[goldsmith]

Dear FvM
Hi
Thank you very much for your reply . but CT hasn't good frequency response and for this range it will has low precision , i think .
And about DC feed back, is your mean that i rectify samples of current ? if yes , thus , an small delay will create .
Thanks
Goldsmith

 

[Sajjadkhan]

How much voltage level are you working with?

 

[goldsmith]

Dear Sajjadkhan
Hi
Thanks for your reply
Short circuit , just .
Regards
Goldsmith

 

[Sajjadkhan]

if you are using low ac voltages then i suggest circuit something like this:
https://freecircuitdiagram.com/2009...a-classic-design-using-positive-rail-sensing/

in your cause since its AC so using a single supply you need to set a quicent point or you may use a dual supply or you may pre rectify the ac signal.

So at output you will get AC voltage use a capacitor to average it and connect a transistor with capacitor if you need to discharge the cap and get another reading.

 

[goldsmith]

Sajjadkhan , thanks for your reply , but i need 10 A , and i don't think it is possible with the way that you told .

 

[Sajjadkhan]

10A will be passing through this 0.2 ohm resistor, else this circuit wont effect you other circuit.

Are you saying that you need to generate 10A also or just u want to detect it?

---------- Post added at 19:55 ---------- Previous post was at 19:54 ----------

Can you post a basic circuit of yours?

 

[goldsmith]

I need to take sample from currents from 0 up to 10 amperes with the precision about 5 ma or 10 ma .
Thanks in advance
Goldsmith

 

[FvM]

And about DC feed back, is your mean that i rectify samples of current ? if yes , thus , an small delay will create.

No I simply suggest to extend the feedback operation to DC by implementing an overall DC coupled loop.

 

[goldsmith]

Dear FvM
Can you describe this way , please ?
Thank you
Goldsmith

 

[FvM]

In feedback topology terms, it's just a current controlled voltage feedback circuit.

Points of interest or the output stage design, which may have either low output impedance (voltage source) or high impedance (current source), the current sense details and of course the frequency characteristic of the controller.

 

[mtwieg]

I'm not clear whether goldsmith wants to actually regulate the current or simply measure it.

Anyways goldsmith, can you explain the nature of the AC current and its load? Does it need to be isolated from the measurement circuitry? Would using a series sense resistor be acceptable? If not, I would look at hall effect current transformers, like those made by LEM.

 

[goldsmith]

Dear FvM and Dear mtwieg
Hi
Thank you for both your replies.
For FvM : are you sure , that if i use resistor as current sensor it's tolerance can't suffer me ?
And for mtwieg : I want take sample from my current but with good precision .
Thank you for your help .
Best Regards
Goldsmith

 

[Sajjadkhan]

Actuall eveyone here is asking you to even post a rough idea diagram so we all can understand better, words are no good. draw it, the source and how its connected to the load and type of load and things like that.

And what do you mean "its tolerance can't suffer me" i didnt get it. wait are you saing you are the source? lolz i dont think so.

Anyways there are .1 and .01 % tolerance resistors which are precision resistors, have a look at digikey.

 

[goldsmith]

Thank you dear all for your guidances and helps i designed it with diagram that FvM introduced and with low tolerance ( zero percent ) high power resistors and diff amp to prevent effect of , the temperature of area .
Thank you again for all of your answers .
Best Regards
Goldsmith