Measuring Current Using ZXCT1041 IC

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I make attached circuit but it cannot amplify AC signal of 300mVAC to approx. ~3VDC.

And datasheet says its gain is 10.

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That circuit measures voltages not current!

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Quote:

I make attached circuit but it cannot amplify AC signal of 300mVAC to approx. ~3VDC.

Why do you say that? What have you connected to the schematic shown? When you do that, are the 'scope traces similar to those in the app note explaining that circuit?

Quote:

That circuit measures voltages not current!

Ummmm--Aren't you nearly always using a voltage to indicate a measured current? See the datasheet and the app note.

http://diodes.com/_files/product...

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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A current measurement has a shunt resistor on top which feeds the device being measure ie a lamp or other. Anyway that circuit will only measure AC, not good for DC current measurements.

So if the OP needs to measure current with that circuit he need to connect a shunt resistor on the GND side and connect the input of the circuit on the side where the power comes in so as to measure the voltage drop across the resistor, a lot more complicated by doable.

At this stage we have no idea of how things are wired up.

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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imranahmed wrote:
I built the attached circuit but it does not amplify an AC signal of 300mVAC to approx. ~3VDC.

And datasheet says its gain is 10.

In this configuration (precision rectifier), the output will be a full wave rectified AC signal with a gain of 10. You will not get a DC output.

 

In consideration of others, please RTFM!

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Quote:

So if the OP needs to measure current with that circuit

Have you looked at the app note, and how the shown circuit works?

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Yes, and I have used some of them in the past (DC version ZXCT1085). He needs the circuit in Fig3 not Fig4. :wink:

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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theusch wrote:
What have you connected to the schematic shown?

More specifically, what is the OUT pin connected to?
Examine the "Error v Resistive Loading" characteristic graph on page 5 of the data sheet,
gain starts dropping significantly with output loading below 1 megOhm.

Shouldn't this topic be moved to the General Electronics forum?

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Can I use this circuit?

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Yes, that will measure current. You do need to watch a variety of conditions, For example, there is a maximum and minimum limit on Vin+. There is a limit on Iload * Rsense for the proper operation. There is also a limit on Rsense * (Iload^2) set by the power dissipation rating of Rsense. There is also a limit on the minimum load resistance.

Within those limits, it is pretty much "dead easy".

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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imranahmed wrote:
Can I use this circuit?

Yes, but it serves an ENTIRELY DIFFERENT purpose than your first circuit. What are you trying to do?

 

In consideration of others, please RTFM!

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Quote:
Can I use this circuit?
NO! Not for AC as you are asking. I'm guessing this is a hobby project?

If not I would be pretty annoyed at the lack of understanding of basic electronics. :wink: (and not just because I'm marking 50 years in the business this month...)

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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jpmargis wrote:
imranahmed wrote:
Can I use this circuit?

Yes, but it serves an ENTIRELY DIFFERENT purpose than your first circuit. What are you trying to do?

Dear jpmargis,

I want to measure AC load current by using Current Transformer.My Ammeter coding is completed and succefully runs on simulation.

Current Transformer is used 100/5A.

I am trying to calibrate ZXCT1041 IC for 0-5A of CT current for input of ADC.
I am using ATmega16@8MHz (AVR studio 4).

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If there is any other IC is available for measuring AC current of CT, so please share with me.

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Quote:
Current Transformer is used 100/5A.
You didn't say that before, so if you are getting an isolated voltage output the first circuit will "sort of" work.

The app note shows 100mV minimum to 800mV maximum input voltage however so it will not measure very low voltages correctly. You may need to use the discrete precision rectifier circuit which is also shown on that note.

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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I would suggest the current monitor configuration (your second circuit). Make Rsense 0.025 ohms at about 2 watts. This will give you about 1.25 volts at the output with a 100 amp load. The math is all from the app note and the data sheet coupled with a little basic electricity. Connect a 1.25 volt precision reference such as an LT1389 to Aref and you should be able to get 100+ conversions per cycle from the ATmega16 ADC to feed your current calculation. Again, the output from the ZXCT1041 will be an AC waveform. Depending on your load, you may need to synchronize with the line voltage to perform an accurate current calculation.

 

In consideration of others, please RTFM!