Can i measure 450nA with a 6000 count DMM or am i better off just doing a voltage measurement across a resistor and employing ohms law?

I have tried to use a DMM but can't get it to respond.

 

that is 0.5uA so not really... proper thing would be to build suitable amplifier. but... you can try using volts range. most DMMs have input impedance of 10MOhm on most ranges. so 0.45uA*10MOhm = 4.5V. so switch DMM to 20V range (0.45uA will display as 4.5V).
if 4.5Vdrop is too much, place 1.1MOhm resistance (1Meg + 100k in series) in parallel with DMM. that will result in voltmeter input resistance drop from 10 to 1 MOhm so voltage would be 10x lower. for 0.45uA you would be seeing 0.45V


something like

 

Yeah i found doing it the conventional way with a DMM i ran out of decimal places.

 

Be aware though, that many autoranging DMMs change their input impedance between 10 and 11 Megohm, as they step through their different ranges. Check the meter’s user manual for range/impedance info and lock it into a manual range.

But if 10% error is close enough for your requirements, then you don’t need to bother.

 

Be aware though, that many autoranging DMMs change their input impedance between 10 and 11 Megohm, as they step through their different ranges. Check the meter’s user manual for range/impedance info and lock it into a manual range.

But if 10% error is close enough for your requirements, then you don’t need to bother.

I am using a PM18 DMM (pictured) which is fully manual at the 60uA range and i get nothing, i tried to measure 100mA on another range and still nothing, i think the fuse is blown for the current ranges and i can't get the thing open so i'll either trash the meter or just use it for the other functions. Another meter i tried works fine.

 

Have you looked in the battery compartment? That is typically where the fuses are located on handheld meters.

 

Hello,

@WBahn, you are right about the location of the fuses.
Read page 22 of the manual.

Bertus

 

Hello,

@WBahn, you are right about the location of the fuses.
Read page 22 of the manual.

Bertus

Page 20 I see tells me I can read resolution to 10nA so I will give this a go and see what I can do thanks

 

The instructions are incorrect, the fuses are inside the unit on the circuit board, i had to take the outer Orange sleeve off the meter and undo another 4 screws to get to them, the 600mA fuse was blown and i replaced it with a 400mA one, put it all back together and it works as new so thanks for your replies people.