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Error Chart Compilation: DC Current

Writer's picture: Paul TaylorPaul Taylor

Time to get out the hard hat! We're going to measure DC Current. This is a slightly shorter list than voltage, because some devices I have don't measure current at all.


By the way, I use Libre Office for graphing. The data is pulled from a single table, then I copy the graph and delete the ones I don't want and leave behind one or more curves.


On to the overall graph of all tested:



Newsflash: The current source for 100 mA and below is brought to you a newly acquired Keithley 220. This device's lowest range is 1.9995 nA!



So that you know, I did calibrate many of the cheap meters in this list. The manufacturers typically throw in a single shunt resistor with "close enough" value. What did I do to to calibrate? By changing the shunt resistor(s) to give me a high reading if necessary, then adding additional high value resistors in parallel to reduce the total shunt resistance, until the reading on the display matches the source. Typically, the PCB provided a space for the second resistor.


Before each graph, I'll list the current sense value - which is the resistance measured at the input jacks when set to the current mode(s). A lower value is better, so that the measurement device has less of an effect on the circuit under test.


0.028 Ω A:


2.252 Ω mA:


0.021 Ω A, 2.47 Ω mA:


0.013Ω A, 1.567 Ω mA


0.016 Ω A, 3.270 Ω mA

0.021 Ω A, 1.137 Ω mA

0.023 Ω A, 1.205 Ω mA

0.019 Ω A, 1.175 Ω mA:

For one of these meters, I removed the 10A input in order to add a 4-wire resistance mode. Therefore that one only measures 200 mA.


0.027 Ω A, 3.181 Ω mA:


The AN8009 (shown below) drops out with precision when transitioning from the uA to mA range. Notice the interruptions of a smooth graph!


It measures up to 999.9 uA then goes OL. After switching to mA, suddenly readings start at 1.0 mA with no additional digits. Very strange for a meter to do this. The same problem did not happen going from mA range to A range.


0.052 Ω A & mA:

The big guy below has a nice range of measures

0.035 Ω A,  1.3 Ω mA, 100 Ω uA:


0.018 Ω A, 2.248 Ω mA

0.021 Ω A, 2.942 Ω mA:

0.040Ω A:


0.032 Ω A:


3.1 Ω mA:


2.772 Ω mA:


Clamp meters using their claws. By not breaking into the circuit, you give away accuracy for sure.


0.022 Ω A, 1.385 Ω mA:


For the meters below, I'm surprised that the portable unit has a better low range than the benchtop version.

0.028 Ω A, 2.142 Ω mA

0.046 Ω A, 2.810 Ω mA:


0.026 Ω A:


0.022 Ω A:


As before, if I boil things down to the most accurate meters for measuring current. The crossover point is 50 mA.


Note: This graph is magnified 5X versus the graphs shown thus far.


In summary, expect a much larger accuracy, and shorter range of measurement for current when compared to voltage measurement capability of multimeters. In order to get good accuracy you might need to take matters into your own hands.


Furthermore, the cheapest offerings use a SMD resistor instead of a thick wire current shunt. These are more sensitive to self-heating. This means the value will quickly change over a few seconds, and the duration of current test must be less than 10 seconds (with cooling in between uses).


The two meters I chose for "best use" use a "proper" current shunt. Something to look for.

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