Measuring Current Without Ammeter: Solutions & Tips

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    Current Measuring
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Discussion Overview

The discussion revolves around methods for measuring electrical current without using an ammeter in series. Participants explore various techniques applicable to integrated circuits (ICs) and the challenges associated with measuring small currents, particularly in the context of existing circuit configurations.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about alternative methods to measure current between ICs without inserting an ammeter in series.
  • Another participant suggests using Ohm's law to calculate current based on known output voltage and input impedance, noting that complexity increases with significant reactive components.
  • A different approach is proposed involving the use of a probe that measures current indirectly through the magnetic field, although its accuracy is questioned.
  • One participant advocates for using a shunt resistor to measure voltage across it as a reliable method for measuring current, particularly for milliamps going to ICs.
  • Concerns are raised about the effectiveness of Hall effect sensors for measuring low currents, especially in DC applications, due to the influence of ambient magnetic fields.
  • Another participant mentions that understanding circuit behavior can often be achieved through Kirchhoff's laws without needing to measure currents directly.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of various measurement techniques, particularly regarding the use of Hall effect sensors and the practicality of shunt resistors. No consensus is reached on a single best method for measuring current in this context.

Contextual Notes

Participants note limitations regarding the accuracy of certain methods, the significance of reactive components, and the challenges posed by ambient magnetic fields in measurements.

Who May Find This Useful

Individuals interested in electronics, particularly those working with integrated circuits and seeking alternative current measurement techniques.

taupune
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Hi people, i got a question regarding current measurement.
Is there a way to measure it, other than by putting the ammeter in series?
How do they find the current output from one IC to another IC and there isn't any resistance or cap between them?

Thank you.
 
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The current into the input is simply a function of ohms law. As long as the reactive part is not significant, if the output voltage is known and the input impedance is known, one simply divides the output voltage by the input resistance. If the reactive component is significant, one still divides the voltage by the impedance but the calculations are more complex.
 
One way to measure currents between ICs etc is to use probe which measures the current "indirectly" via the magnetic field. The accuracy isn't great, but it works

This is also a very commong technique when dealing with higher currents through e.g.; you can buy so called current clamps that can be be with an ordinary multimeter.
 
Really, the best way is to use just to use a shunt resistor and measure the voltage across it. Hall effect sensors can work as well but are typically very inaccurate as f95toli said. Since you mentioned that you want to measure current going to ICs, i.e. milliamps, your only practical choice is to just use a shunt resistor.
 
Topher925 said:
Since you mentioned that you want to measure current going to ICs, i.e. milliamps, your only practical choice is to just use a shunt resistor.

I suspect that he is referring to ICs already soldered onto a board
 
I don't think Hall devices are any good for measuring a few milliAmps, which is the maximum that the typical circuitry uses 'between devices. mA of AC is fine to measure but DC is a problem because the ambient field is significant and can't totally be 'zeroed out'. If you have a fault, you can normally deduce what's going on without having to know the currents between all components - Kirchhoff 1 will often tell you.
 

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