Learning how to take light measurements with a DMM

I am using this article to teach me: http://www.candlepowerforums.com/vb/showthread.php?236906-Simple-guide-to-using-a-DMM-for-measurements

Light:

Solarforce L2P host

5 mode XM-L T6 drop-in (not sure which model it is)

Trustfire 18650 flame cell 2400Mah @ 4.04Volts

Now doing a current consumption test I get these results (the first test in the article):

I get nothing at all, the meter reads 0.00, what is going on? My test leads are in the 10A unfused and com slots. I am using the scale for A and tried 20m and 200m in the A scale.

TailCap:

0.3 ohms meter set to 200ohm scale (lowest it has)

Make sure the DMM is switched to the 10A range. With the tailcap off of the light, touch the black lead to the negative end of the battery and the red lead to the bare threads of the light (anodizing doesn't conduct electricity, so you have to touch bare metal). The DMM will complete the circuit instead of the switch. The positive end of the battery should still be in the light touching the spring in the head, just like it usually does.

Also to note, you will be needing to cycle the modes by taking the DMM lead off of contact for a moment, then back on.

One of the things I've noticed with my fairly expensive meter, is that if you accidentally select the lower current bracket on the DMM, then it will do some current limiting to the driver. Hence, the "set it to 10 A" is good advice if you want real readings.

OK my leads are red in the 10A unfused slot, black in the Com slot, DMM is set to the 10A scale. Black lead is at back of battery in the light and I have plenty shiny metal on the treads for red lead, still get nothing. :) Could the meter be fried? It has a funny smell to it yet it will read battery voltage and to the tailcap test. It is a $12 autoparts store meter.

If your meter is kinda crappy, the funny smell might be from the lack of a fuse, but I'd be more worried about the battery if you put it in backwards.

The battery in the flashlight is in the right way, the meter was taken apart and it is powered by a 9v which goes in one way and it does have a fuse in it. The fuse is good, but guess what, the three ports where you put the leads in from the inside are burnt looking, smell bad, and have a corrosion white look to them. I think I fried the DMM. :( I did not use the 10A setting at first, so it was my fault. I used what they said in the article not knowing any better. Who makes a good DMM on a budget? LOL

You can't fry a meter if you only put it on the wrong setting with the leads in the right holes, only if you tried to put too much current through the ports.

Just get the cheapass one from harbor freight.

Another reason to start off with cheap equipment and move up to more expensive stuff later. Sounds like it may well be fried. You have to use the 10A port and the COM port and switch the DMM to 10A.

I bought this one at Amazon for about $7. The price varies. There are a lot of very similar ones all over. There is also one on eBay for pretty cheap but it is from overseas, so it will take a while.

This one on eBay is $4. I ordered one, got it, and my puppy chewed it up before I could even try it out. Someone else here liked it though:

http://cgi.ebay.com/LCD-Digital-Multimeter-Voltmeter-Ammeter-Meter-OHM-DVM-/330578539400?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item4cf8043388

Well looks like I need a new DMM. LOL :) Now I know. I will have to order the Amazon model, for the price no need to wait for post from China.

Depends on how much you value your own safety. But hey whatever, I use recycled unprotected 18650's.

Those are the same design (ic inside) as the cheap hb ones.



Another reason to start off with cheap equipment and move up to more expensive stuff later. Sounds like it may well be fried. You have to use the 10A port and the COM port and switch the DMM to 10A.

That's not how he burned his, though. He probably tried to measure tail current across a shorted batter or w/ the 400ma port.

What about this model here? Good idea or overkill?

http://www.amazon.com/Equus-3320-Auto-Ranging-Digital-Multimeter/dp/B000EVYGZA/ref=sr_1_17?ie=UTF8&qid=1308712950&sr=8-17

I had that in my cart before I found the almost-free HF ones work adequate enough to bother clicking buy on it. I didn't get the other cheapos because they didn't have backlight (and equus doesn't either but it's got the big lcd). Go for it.

Now when I get me another meter to replace the one I broke I will keep learning and go from there. Oh well glad it was a cheap meter and not a $200 Fluke.

I think you didn't set the dmm to 10AA. I did that myself once ( a long time ago)

Not that a Fluke can't be smoked, but you do have to try pretty hard.

I'm amazed at the blunders I've done and my Fluke has survived. (Like leaving it on continuity while I'm checking the output of a power supply.)

For some fun check out www.eevblog.com/2010/05/05/eevblog-84-high-energy-multimeter-destruction/ its about 12 minutes long and is quite entertaining.

I just got this guy in the mail today:

http://www.amazon.com/Equus-3320-Auto-Ranging-Digital-Multimeter/dp/B000EVYGZA/ref=sr_1_17?ie=UTF8&qid=1308712950&sr=8-17

I now know what I did wrong before so now I can learn by playing with my Solarforce L2p. :)

Bad news, that meter maxes out at 200ma or .2 amps your XML lights pull over 3 amps or 3000ma. So if you try to measure amperage you will melt that meter or pop the fuse if it has one. I am a mechanic so I bought a Fluke 179 for work and when I popped the fuse it cost $12 dollars for just the fuse. I am sure someone will chime in with a budget meter that will do what you want it to.

eeerrr, hmmm that is not good. Well here I was thinking I was making a good choice. LOL :) Hmmm, now what? LOL Here are the specs from the manual:

SPECIFICATIONS
GENERAL SPECIFICATIONS AND FEATURES

3-1⁄2 digit LCD display (maximum reading of 2000); 3 LEDs;
green, yellow and red
Auto Range (ACV, DCV, Ohm, AC mA, and DC mA)
Automatic negative (-) polarity indication
Automatic zero adjustment
Over range indicator (except 10 A function). Displays "OL" on
LCD
Low battery indicator. Displays battery symbol
on LCD
Automatic power shut off (after 15 idle minutes)
Pollution Degree 2
Measuring circuit category II
Operating environment:
Temperature - 32° to 104° F. (0° C to 40° C)
Humidity - Less than 80% relative humidity (non-condensing)
Altitude - up to 6562 ft (2000 meters)
Storage environment:
Temperature - 4° to 140° F (- 20° to 60° C)
Humidity - Less than 90% relative humidity (non-condensing)
Power Supply: Two 1.5V AA batteries
Fuse: 315mA/250V 5X20 mm (Radio Shack, GMA/217
series; #270-1046) fuse
Dimensions:
Height - 5.50 in. (139 mm)
Width - 3.50 in. (89 mm)
Depth - 1.25 in. (32 mm)
Weight (including batteries): approximately 6.3 oz (180 g)
ELECTRICAL SPECIFICATIONS
DC VOLTS
Range Resolution Accuracy
200.0mV 0.1mV
2000V 1mV
20.00V 10mV
200.0V 100mV
600V 1V
3
E
Notes
±(0.8% of Input Resistance: 10MΩ
reading
Overload Protection: 600V DC
+ 5 digits) or AC 600V RMS.
AC VOLTS
Range Resolution Accuracy
2.000V 1mV
20.00V 10mV
200.0V 100mV
600V 1V
Notes
Input Resistance: 10MΩ
±(1.2% of Overload Protection: 600V DC
reading
or AC 600V RMS.
+ 5 digits) Frequency Response:
50Hz - 400Hz
RESISTANCE (OHMS)
Range Resolution Accuracy
200.0Ω 100mΩ
2000kΩ 1Ω
20.00kΩ 10Ω
200.0kΩ 100Ω
2.000MΩ 1kΩ
20.00MΩ 10kΩ
Notes
±(1.0% of
Overload Protection: 250V DC
reading
+ 5 digits) or AC RMS.
±(2.0% of
reading
+ 5 digits)
DC AMPS
Range
Resolution Accuracy
Notes
±(1.0% of Overload Protection: Fuse
reading
315mA/250V
200.0mA 100μA
+ 5 digits) Input Voltage Drop: <0.2V.
±(2.0% of Unfused; 15sec maximum
2.000A
1mA
reading
Input Voltage Drop: <0.2V.
*10.00A 10mA
+ 5 digits)
*A waiting period of at least 15 minutes is necessary between
every 15 second testing period.
20.00mA 10μA
AC AMPS
Range
Resolution Accuracy
Notes
20.00mA 10μA
±(1.5% of Overload Protection: Fuse
200.0mA 100μA
reading
315mA/250V
+ 5 digits) Input Voltage Drop: <0.2V.
4
E
BATTERY TEST (LEDs)
When the voltage of the battery being tested is lower than
10% of its rated voltage, the red LED will not light.
Load
Range Resolution Current Accuracy
1.5V 0.001V 10mA
(approx.)
6V 0.01V 100mA
(approx.)
9V 0.01V 10mA
(approx.)
12V 0.01V 200mA
(approx.)
Notes
Green LED: 1.30V
±0.075V and up.
Yellow LED: 0.94V
±0.075V to 1.29V
±0.075V.
Red LED:0.15V±0.075V
to 0.93V±0.075V
Green LED: 5.22V
±0.3V and up.
Yellow LED: 3.76V
±0.3V to 5.21V±0.3V.
Red LED:0.6V±0.3V to
±(5% of
3.75V±0.3V
reading
+ 5 digits) Green LED: 7.83V
±0.45V and up.
Yellow LED: 5.64V
±0.45V to 7.82V±0.45V.
Red LED:0.9V±0.45V to
5.63V±0.45V
Green LED: 10.44V
±0.6V and up.
Yellow LED: 7.52V
±0.6V to 10.43V±0.6V.
Red LED:1.2V±0.6V to
7.51V±0.6V
DIODE/CONTINUITY TESTS
Function Range Resolution Description
Diode Test 2V
1mV
Test Current:
1±0.6mA
Test Voltage:
Approx. 1.5V
Continuity 200Ω
Test
5
E
0.1Ω
Note
Overload
Protection:
Approx. 120Ω or 250V DC or
AC RMS
less, buzzer
(beeper) will
sound

OK I think I was wrong I was reading a review that said 200ma max but I see a DC 10A selector in the picture so you should be good . Set the knob to DC10A put the red wire into the one marked DC10A and black to ground and test away.



That's for AC current measurements.

added: I replied before I saw your last msg.