The leads for a DMM does not affect the current calibration.
But the current consumption of a light will change with the resistance in the DMM and test leads!
The current consumption will also change with the battery quality and charge state.
I can use any leads I want on any of my meters and they will show the same current (When using a current source and not a flashlight):
also the impression i get from all the topics ive read. all i can say is my dad had this craftsman for ever, and got a new one for cheap and swore that this craftsman was off because it didnt match the readings of his new one. he was going to toss it, but i didnt have one and wanted it. ive compared readings to the ohms law many times and am always very close if not spot on.
find a little set up to test ohms, voltage, and amps under load. then goto the ohms calculator and compare your readings. type in the ohms and voltage under load, then calculate what the amps should be, and see how close it is to the law
My experience has been the opposite. It does 2.82A on eight 7135s on the short 5-inch leads. It's a Uni-T UT-58E. It gives you 2 pairs, one short and one 110cm long. The 110cm long one is giving very low readings.... in fact just over 3 amps on the DRY triple XM-L on freshly charged Sanyo 2600s (the ones which gives me the highest current, even higher than Panasonic 2900 and 3100s).
Get a lux meter and do relative readings compared to various branded lights with known OTF outputs. You will experience the sag due to heat and output cut due to glass etc.... It's better info than any $2000 DMM.
Agreed!
How can a DMM be calibrated to an accessory which is removable? Even Fluke has an assortment of leads that certainly have varying resistance.
I cannot believe that to be true.
EDIT: After thinking about it, and with my very limited knowledge, I'd guess they are calibrated using an very precise constant current power supply which would negate the effects of resistance of in the circuit. The power supply delivers the current regardless of resistance and allows the DMM to be accurately calibrated. Looking up info on 4-wire low resistance testing made a light bulb go off in my brain. :)
The MM Leads add resistance to the circuit [ testing current = flashlight ] so therefore , depending on the resistance added , will dictate current ...
So the lower the resistance , the more true the reading .. Now we are forgetting the clicky switch ...
It also adds resistance , so to get a more accurate picture of flashlight performance [ current draw ] it would need to be in the circuit ...
Then you would have a true idea of current draw ...
Again lower resistance leads would result in a more accurate reading ...
One way to test this is with a current limited light - Like 1.4A , 2A 3A .. And knowing current is limited to such then test leads to see what effect they have ...
I have some of those 7135 x 6 drivers on the way ..
But the plan is to see what's what .. Test Leads wise .... and how thick you need to go to get low resistance ... [ Something interesting to test ]
if anybody wants to measure low(er) resistance, I can recommend this little cheap LCR DMM:
It is not a professional equipment, but it has 10milli ohm resolution, this is quite enough for checking tailcap, connections, DMM resistance etc.
The problem with this is connection and probe resistance, you have to be very careful to avoid large errors from that.
Using a 4 terminal measurement is much safer, this can either be done with a meter that has it (Present on many bench DMM, but not a budget solution) or with a power supply and a regular DMM (See my guide).
Yes, I know that. I have a labor PS and can measure low resistance. I can say, that it is quite accurate for this price for amateurs. It is necessary to replace the leads, no question. First, you have to measure self resistance of Dmm+leads, after that you can calculate the "real" resistance of a tailcap for example.
And you have to press the probes strongly to the metal parts of course.
I actually took the worst leads and made them shorter, now about 30cm top to toe.. and they give a higher reading, but still not as high as my 2 other test leads. Anyway, just wanted to add this related to my earlier post in here
Just to clarify. You are saying leads are not calibrated into the DMM? Or is it?
When you say you can use any leads you meant any leads that are not current limited right? Have you tried using thin long leads and did it give a smaller current reading?
Sorry, I missed this question.
It is not, you can use any leads you want, but ohms law can get you into trouble!
You might loose some volts when using thin long leads. When measuring on a flash light, the meter will show a different value, than when using short thick leads. This has to do with ohm law, not calibration.
When measuring on 230V, it is not a problem with a few volts drop and the meter will show the same value.
That's how I understood it. Thanks for clarifying. So in conclusion using thicker shorter leads is advisable to get max current draw of the flashlight(sans switch).