Hi!
I'm trying to find a DMM that performs well in Dave's infamous "white LED test" - can it light and take a reading from a decent LED? I note from his $100 multimeter shootout video that the Fluke 87-V has no problem in this respect.
So, I had a look at its user manual (.pdf here
http://docs-europe.electrocomponents.com/webdocs/0adc/0900766b80adcb1d.pdf) which says on p.51 that in diode mode, it has an open circuit test voltage of 3.9vDC and a current of 0.6mA.
In the same video, the BK Precision 2709B can't cope with this test - it lights up the LED but can't display a reading. Looking at the datasheet for this DMM (.pdf here
http://www.bkprecision.com/downloads/datasheets/2709B_datasheet.pdf), it says on p.1 that it has an open circuit voltage of 3.5vDC at a current of 1.2mA.
So, on paper, I'd expect the BK to perform pretty much as well as the Fluke in this regard, although there's clearly something I'm not understanding properly, as I'd expect an LED to need more like 15-20mA to light up like that rather than less than 1mA.
If anyone can explain this to me, or let me know what I should be looking for in spec sheets to make sure DMMs can perform this task, I'd be very grateful! Or is it one of those things you can only test when you've actually got your hands on the meter?
Thanks ever so much.