Measuring current when prototyping

Thread Starter

StrongPenguin

Joined Jun 9, 2018
235
Ho do you guys measure curren when you are creating a board, whilst in the breadboard stage?

I have a Fluke, but that is normally in use for other stuff.

Any instruments you can reccomend?
 

KMoffett

Joined Dec 19, 2007
2,877
Buy a couple cheap digital meters. Many on Amazon, eBay, Banggood, and Aliexpress for under $10. If "trusted" accuracy at some point is needed then switch in the Fluke. I keep several of these cheap meters around my bench, garage, and at work. They've shown to be accurate enough for quick testing.
 

schmitt trigger

Joined Jul 12, 2010
242
Exactly what KMoffet said. This is also my preferred method.

Also when you receive the cheap units, you can always perform a "sanity check" eith your Fluke to review its accuracy.
Most of those meters have a trim pot, and you can tweak it to improve its accuracy, if required.
 

Thread Starter

StrongPenguin

Joined Jun 9, 2018
235
Thanks for the advice, all. I will buy a couple of cheap multimeters.

@dl324 That is what I have been doing so far, but pretty annoying when a potmeter is involved. And I like to see numbers.
 

dl324

Joined Mar 30, 2015
10,757
That is what I have been doing so far, but pretty annoying when a potmeter is involved. And I like to see numbers.
Couldn't you just insert a fixed resistor in series with the pot and put a DVM across it? DVMs aren't very expensive these days. I have half a dozen free Harbor Freight DVMs that are good enough for most voltage measurements.
 

BobaMosfet

Joined Jul 1, 2009
1,108
Ho do you guys measure curren when you are creating a board, whilst in the breadboard stage?

I have a Fluke, but that is normally in use for other stuff.

Any instruments you can reccomend?
Put a 1-Ohm, higher-wattage resistor as your 'jumper' to the ground-rail and measure across it with a DVM on DC Volts setting. That will give you your wattage rating. This will get you the ballpark value you can use to determine where your circuit is at. Simple, easy. I use a 1-Ohm resistor because of the ratiometric relationship in Ohm's Law.
 

DickCappels

Joined Aug 21, 2008
6,388
Per BobaMosfet, buy several 10Ω, 1Ω, .01Ω and if you will be measuring higher current lower reistance resistors and operate your DVM in the voltage measurement mode. After having to stop work while you chase down a replacement DVM fuse a couple of times you will come to appreciate the superiority this approach.
 

Thread Starter

StrongPenguin

Joined Jun 9, 2018
235
Nice trick with the fixed resistor. Never really thought of that. I am going to buy a bunch of them, in various sizes.

Should they be higher watts? Like 1/2? Or 1w?
 

dl324

Joined Mar 30, 2015
10,757
Should they be higher watts? Like 1/2? Or 1w?
It depends on the currents involved. 1A through a 1 ohm resistor is 1W. If you reduce the resistance to 0.1 ohms, you only need 1/8W.

I use some 0.2 ohm 1% 8W in TO-126 package because I have a bag of them that I picked up in an eBay auction.
mp808.jpg
 

Reloadron

Joined Jan 15, 2015
5,455
Buy a couple cheap digital meters. Many on Amazon, eBay, Banggood, and Aliexpress for under $10. If "trusted" accuracy at some point is needed then switch in the Fluke. I keep several of these cheap meters around my bench, garage, and at work. They've shown to be accurate enough for quick testing.
That's what I would do.

Ron
 
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