Finally Got A Cob Lit Up! Multi-meter Questions

nfhiggs

nfhiggs

Well-Known Member
CCCmints said:
Like this? https://www.amazon.com/Topone-Digital-Meter-Voltmeter-Multimeter/dp/B005EK3NRS#Ask



So I can measure either A/C (with the device you mentioned) or D/C (with a DVM) and achieve the same results? What is the difference between measuring A/C vs. D/C? Is one more accurate than the other?
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To figure out the DC current from the AC line measurements, you have to do a bit of math as well as knowing your power supply's efficiency factor. Measuring it directly is MUCH more exact.

The meter you linked to will do it directly - just not sure how accurate a $12 meter is going to be, but it will be at least as accurate as measuring the AC side.

To measure the DC current, you will put the meter in series with the strips. Connect the positive wire from the power supply to your red meter lead, then touch the black meter lead to the strips positive connection point.
 
CCCmints

CCCmints

Well-Known Member
nfhiggs said:
To figure out the DC current from the AC line measurements, you have to do a bit of math as well as knowing your power supply's efficiency factor. Measuring it directly is MUCH more exact.

The meter you linked to will do it directly - just not sure how accurate a $12 meter is going to be, but it will be at least as accurate as measuring the AC side.

To measure the DC current, you will put the meter in series with the strips. Connect the positive wire from the power supply to your red meter lead, then touch the black meter lead to the strips positive connection point.
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What do you mean by 'strips'?
 
nfhiggs

nfhiggs

Well-Known Member
CCCmints said:
Sweet so then I could wire them up in series and measure both a/c & d/c.
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I've got similar displays. I can't attest to those particular ones, but I can tell you the accuracy of some of these little displays is all over the map. The first one's I had worked well - they were close to the readings I got with my handheld multimeter. Then I got some more - different seller and slightly different displays - and they were not so accurate - they were off by about 50% compared to my multimeter. Then I went back to the first seller and got a couple more - they seem to be accurate like the first ones.
 
CCCmints

CCCmints

Well-Known Member
nfhiggs said:
I've got similar displays. I can't attest to those particular ones, but I can tell you the accuracy of some of these little displays is all over the map. The first one's I had worked well - they were close to the readings I got with my handheld multimeter. Then I got some more - different seller and slightly different displays - and they were not so accurate - they were off by about 50% compared to my multimeter. Then I went back to the first seller and got a couple more - they seem to be accurate like the first ones.
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nfhiggs said:
I meant your COBs. Had you mixed up with another guy using strips. My bad.
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Yeah, I'll probably just grab a meter in the $30-$40 range. It should be accurate enough.
 
psychedelicdaddi

psychedelicdaddi

Well-Known Member
CCCmints said:
So I failed in wiring up the multimeter with my COB. When I plugged the power in, the COB didn't light up. I made a diagram for the wiring to make sure I didn't fuck anything up in the first place: https://imgur.com/KfMS8iY

A/C In: https://imgur.com/d6aVoyk
D/C Out: https://imgur.com/Fs0ZXFe
Multimeter to COB: https://imgur.com/JyVDS6P

If someone could point out a mistake if they see one it'd be greatly appreciated.
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Where's the blue wire going on the dc out?
 
nfhiggs

nfhiggs

Well-Known Member
CCCmints said:
So I failed in wiring up the multimeter with my COB. When I plugged the power in, the COB didn't light up. I made a diagram for the wiring to make sure I didn't fuck anything up in the first place: https://imgur.com/KfMS8iY

A/C In: https://imgur.com/d6aVoyk
D/C Out: https://imgur.com/Fs0ZXFe
Multimeter to COB: https://imgur.com/JyVDS6P

If someone could point out a mistake if they see one it'd be greatly appreciated.
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On the AC In - connect the Black wire (on the plug side) to the Orange wire (on the driver side) and disconnect the red meter lead.

On the DC Out - Connect your Red meter lead to Blue wire from the driver output. It should light up and you'll get a meter reading.
 
CCCmints

CCCmints

Well-Known Member
nfhiggs said:
On the AC In - connect the Black wire (on the plug side) to the Orange wire (on the driver side) and disconnect the red meter lead.

On the DC Out - Connect your Red meter lead to Blue wire from the driver output. It should light up and you'll get a meter reading.
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It works!!! Thank-you!! The meter reads 1.380a for a 1.4a driver turned all the way up, so very accurate!
 
ANC

ANC

Well-Known Member
Use cheap meters in the middle of their range.
The only time it is worth dishing out on a Fluke is when you have to take very small measurements. fractions of ohms, currents, and voltages.
A meter with a limit of 10A will be most accurate around 5A. Ther is no reason for such precision here though, measure the voltage crosscheck the datasheet chart and that should be close enough.
 
CCCmints

CCCmints

Well-Known Member
ANC said:
Use cheap meters in the middle of their range.
The only time it is worth dishing out on a Fluke is when you have to take very small measurements. fractions of ohms, currents, and voltages.
A meter with a limit of 10A will be most accurate around 5A. Ther is no reason for such precision here though, measure the voltage crosscheck the datasheet chart and that should be close enough.
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I'm trying to dim to a specific amperage and will likely be doing a lot of that in the future so I'm fine with having spent $125 for the Fluke meter. Especially since I mistakenly purchased the wrong meter when going the cheap route in the first place.
 
ANC

ANC

Well-Known Member
Remember flukes need professional calibration every now and then to stay accurate.
Look after it like a baby.
 
dstroy

dstroy

Well-Known Member
Usually you only calibrate if you need accurate measurements to six digits, or microvolts (a millionth of a volt), in places where it is impractical to bring bench equipment, OR for critical applications where a hundred mV or mA would cook an expensive piece of equipment or kill someone. And then you do it annually. For our purposes it's completely unnecessary to spend $70 on professional calibration annually. Measuring amperage is accurate across the entire available range on all of the fluke meters that I've used, personally and for work.

The resistor arrays used for reference are very stable. If you want to learn more about DMM or electronics in general check out eevblog on youtube, dave does a good job of teaching.
 
nfhiggs

nfhiggs

Well-Known Member
dstroy said:
Usually you only calibrate if you need accurate measurements to six digits, or microvolts (a millionth of a volt), in places where it is impractical to bring bench equipment, OR for critical applications where a hundred mV or mA would cook an expensive piece of equipment or kill someone. And then you do it annually. For our purposes it's completely unnecessary to spend $70 on professional calibration annually. Measuring amperage is accurate across the entire available range on all of the fluke meters that I've used, personally and for work.

The resistor arrays used for reference are very stable. If you want to learn more about DMM or electronics in general check out eevblog on youtube, dave does a good job of teaching.
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Yeah, Flukes are not known to be "drifty". Very seldom have we gotten word back from Tektronix (the cal vendor we use) that one of our meters was out of spec (they are require to notify us). When that happens its a VERY BIG DEAL. We have to re-evaluate all the items we have tested with the meter since its last Cal.

IMO, Calibration is something you need to do if you require traceability.
 
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