How to measure current?

how can I measure the current in the scale of microampere in Arduino?
and how can I record that data?

Simple MC cannot digitize current directly but voltage only.
To measure current you need additional current to voltage converter (trans-impedance amplifier).
Actually this may be a simple circuit with OpAmp.
Check the link below:

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A simple answer would be to write it down.

Perhaps explain what you are actually trying to do, what the project is, then you can get suggestions on recording data that are appropriate to the actual project.

Lots of different ways of recording data.

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Run the current through an appropriately sized resistor and measure the voltage over it. If this may work for you, depends on this:

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Hi, @akashmistry12
Welcome to the forum.

Can you please tell us your electronics, programming, arduino, hardware experience?

To measure micro amps you will need a shunt to measure the voltage across, unfortunately the size of shunt would probably be too large when inserted in series with the circuit you are measuring to give readable results in an Azrduino.

You will need to include an instrumentation amplifier between a small shunt and the controller.

I suggest you Google;

arduino measure current microamps

There are many links explaining the requirements of such a project.

Tom.... :smiley: :+1: :coffee: :australia:

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I want to measure current of photodiode and LDR

Photodiode: use a transimpedance amplifier. Google it; many examples available.
LDR: does not generate current. You typically make either a resistor divider where one part is the LDR and the other is a known, fixed value resistor and measure voltage at the junction, or you attach the LDR to a constant current source and measure the voltage that develops over it.

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Yeah... With an LDR you've got a fixed series resistor so you just measure (or calculate*) the voltage across the resistor and calculate the current with Ohm's Law. Assuming this is part of an Arduino circuit the voltage should be easily measurable by the Arduino (assuming "approximately normal" conditions).

I've never used a photodiode (or phototransistor) but low-voltage or low-current that requires amplification can be tricky and it's more prone to noise. A phototransistor will give you more voltage/current to work with and you'll probably get a more stable/reliable measurement.

  • If the fixed resistor is in the "top" of the voltage divider you'll have to subtract the power supply voltage to get the voltage across the resistor.
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A fairly simple measurement of, let's say, ambient light levels using a photodiode isn't all that difficult. Yes, it's a very high-impedance front end, but with a few precautions and perhaps some averaging of measurements in software you can get a pretty clean output with fairly simple means.

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PS: if interested, this application note from Hamamatsu outlines a number of amplification approaches. It's very concise and useful:

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