(Electronics newbie here, please have patience!)
TL;DR:
Which method should I use to measure a small current, in the order of 1uA-1 (3.3-5V)?
Details:
I recently picked up an interest in electronics, and I have been playing around with the Arduino and various sensors and components. As part of that I've been trying to educate myself on how to measure current (DC, microamps all the way up to hundreds of milliamps) without "cheating" by using a multimeter capable of measuring that range or buying the uCurrent - it sure would be easier, but what's the fun in that, right?
Apart from pure curiosity the reason why I'm even looking at this is because I'm going to try my luck wiring up various battery powered devices - think: home automation etc. in the 3.3-5V range - and I want to verify that they live up to the expectations in terms of power consumption. However, I'm at the point where I could really use some helpful nudges in the right direction.
I've read up on everything from transimpedance amplifiers, current sensing amplifiers, hall effect sensors, the uCurrent project, the "lightning bug" as well as a number of threads both here and in various other forums, but I'm afraid they have me more confused now than I was before I started.
Specifically, I have tried setting up both a current sensing op amp with a small (0.1ohm) burden resistor as well as a variant of the uCurrent/"lightning bug" with two op amps (one to supply the floating reference voltage and the other for the actual amplification), but so far I haven't been anywhere close to getting the expected results.
I can provide schematics for the circuits I've tried (all of them involving one or more op amps), but before I do so I'd like to take a step back and get some guidance when it comes to what the pros & cons are of the various methods, like:
* transimpedance amplification
* current sensing using a shunt resistor
* hall effect
* <other methods go here>
What is the "best" method for me?
Various data points which may or may not help reduce the scope of the problem:
* I'm expecting to use my Fluke 117 to present the actual data (it can do mV DC, but not mA/uA)
* I'm mostly interested in measuring the current when the devices are idle/powered down, so the primary use case is measuring a mostly steady but small (average) DC current
* the precision and accuracy really isn't so important to me, I'm more after the magnitude of the current (1uA-1A)
* I don't need auto-ranging etc.; if I need to manually switch between resistors or whatever that's all fine
* <further limitations/simplifications as needed>
Any and all help is much appreciated, including pointers to helpful tutorials on the subject!
Thank you!
TL;DR:
Which method should I use to measure a small current, in the order of 1uA-1 (3.3-5V)?
Details:
I recently picked up an interest in electronics, and I have been playing around with the Arduino and various sensors and components. As part of that I've been trying to educate myself on how to measure current (DC, microamps all the way up to hundreds of milliamps) without "cheating" by using a multimeter capable of measuring that range or buying the uCurrent - it sure would be easier, but what's the fun in that, right?
Apart from pure curiosity the reason why I'm even looking at this is because I'm going to try my luck wiring up various battery powered devices - think: home automation etc. in the 3.3-5V range - and I want to verify that they live up to the expectations in terms of power consumption. However, I'm at the point where I could really use some helpful nudges in the right direction.
I've read up on everything from transimpedance amplifiers, current sensing amplifiers, hall effect sensors, the uCurrent project, the "lightning bug" as well as a number of threads both here and in various other forums, but I'm afraid they have me more confused now than I was before I started.
Specifically, I have tried setting up both a current sensing op amp with a small (0.1ohm) burden resistor as well as a variant of the uCurrent/"lightning bug" with two op amps (one to supply the floating reference voltage and the other for the actual amplification), but so far I haven't been anywhere close to getting the expected results.
I can provide schematics for the circuits I've tried (all of them involving one or more op amps), but before I do so I'd like to take a step back and get some guidance when it comes to what the pros & cons are of the various methods, like:
* transimpedance amplification
* current sensing using a shunt resistor
* hall effect
* <other methods go here>
What is the "best" method for me?
Various data points which may or may not help reduce the scope of the problem:
* I'm expecting to use my Fluke 117 to present the actual data (it can do mV DC, but not mA/uA)
* I'm mostly interested in measuring the current when the devices are idle/powered down, so the primary use case is measuring a mostly steady but small (average) DC current
* the precision and accuracy really isn't so important to me, I'm more after the magnitude of the current (1uA-1A)
* I don't need auto-ranging etc.; if I need to manually switch between resistors or whatever that's all fine
* <further limitations/simplifications as needed>
Any and all help is much appreciated, including pointers to helpful tutorials on the subject!
Thank you!