Designing an AC Ammeter with 0.15V Voltage and Currents of 200mA, 500mA, 1A

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Discussion Overview

The discussion revolves around the design of an AC ammeter that utilizes a successive approximation ADC, with a specified voltage of 0.15V and individual entrance resistors for measuring currents of 200mA, 500mA, and 1A. Participants explore various aspects of the design, including signal conditioning and handling AC signals.

Discussion Character

  • Technical explanation
  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant requests suggestions for building an AC ammeter with specific parameters.
  • Another participant inquires about the necessary functional blocks for signal conditioning outside the ADC and asks about the frequency range and bit resolution for the ADC.
  • A participant mentions the AD572 as a potential 12-bit successive approximation ADC for the design.
  • There is a reference to a previous post that discusses an AC ammeter design, noting that a shunt is optional and primarily applicable for DC measurements.
  • It is suggested that filtering with a large capacitor may be necessary for the meter input to achieve a steady readout.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the design specifics, and multiple viewpoints regarding the implementation and components remain. The discussion includes both suggestions and questions about the design process.

Contextual Notes

Participants have not clarified the frequency range of the AC signals to be measured or the specific requirements for the ADC's bit resolution, leaving some assumptions unresolved.

micul1987
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Hello all!

I must design an ac ammeter which uses successive approximation ADC,has a specified voltage of 0,15V and individual entrance resistors for measuring currents of 200mA,500mA,1A.

Any suggestions on how to build such a device would be highly appreciated!
 
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micul1987 said:
Hello all!

I must design an ac ammeter which uses successive approximation ADC,has a specified voltage of 0,15V and individual entrance resistors for measuring currents of 200mA,500mA,1A.

Any suggestions on how to build such a device would be highly appreciated!

Welcome to the PF. What can you tell us about A/D conversion? What functional blocks do you need to have outside the ADC for signal conditioning? How do you plan to handle the AC aspects of this design problem? What frequency range AC do you need to handle, and how many bits will you use in your ADC?
 
I have found the AD572 which basically is a 12-bit successive approximation integrated circuit a/d convertor.
 
You could have a look at this post which describes an AC ammeter (1st diagram):

https://www.physicsforums.com/showpost.php?p=2503935&postcount=5

Read the whole thread here:
https://www.physicsforums.com/showthread.php?t=365063

The shunt is optional and the current meter shown just works on DC.

The shunt could be across the meter if you like. This gives a more linear readout for the meter but results in some drop in the supply voltage due to diode drops.

For an A to D converter, the meter input should be filtered with a large capacitor to get a steady readout.
 

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