Testing multimeters

[signcrafter]

I just bought a new blue point meter, http://www.garagejournal.com/forum/showthread.php?t=202558. I already have a fluke 16 and a fluke 77. I decided t hook them all up to a battery just to compare them to each other. The two flukes read 12.49 and 12.50, almost the same. But the blue point meter was reading 12.64. Seems like a pretty big difference. Is this a pretty good sign that my new to me meter is off? If it is, is there a way I can calibrate it myself by using the two flukes I have as reference?

 

[zkling]

O boy, diving in deep here.

In short, Yes and Yes. What you really need is a calibrated bench standard power supply to check against. The Flukes may be reading low (doubt it), the BP may be reading high (probable). And none right on the mark.

Try checking different voltages in both AC, DC and see how they compare over a large range. Is the BP always higher? Also try switching the leads of different meters around, see if they readings change with different leads.

You can calibrate it by adjusting the trim pots inside the case. However, unless you have something accurate to calibrate it against it is just a waste of time.

 

[JJThrasher]

I'd ask your dealer. They can check impacts and torque wrenches on the truck. Idk about DMMs though.

Sent from my SCH-I535 using Tapatalk 2

 

[RPH]

Off by 1.12% from the flukes. Leave it alone.

 

[joedodge]

It'll be close enough for most automotive type work.

 

[Strassi_Br]

try this first

1. Turn the dial to the lowest Ohm seting
2. Touch the black ground point to the red lead point and look at the readout of the multimeter. If it reads 0-0.5 Ohms is a good multimeters.
3. If possible press the calibration button on the face of the multimeter, while still holding the probes together, until .000 appears on the screen.

If you dont have a calibration button ask your dealer for information

 

[celticbhoy]

But how about when it comes to parasitic draws? That 1.12% isn't doing you any favors. I don't know if they can calibrate it, but I want my meter to be as accurate as possible and that BP would drive me nuts, but that's just me.

 

[86k10]

try this first

1. Turn the dial to the lowest Ohm seting
2. Touch the black ground point to the red lead point and look at the readout of the multimeter. If it reads 0-0.5Ohms. its a good multimeters.
3. If possible press the calibration button on the face of the multimeter, while still holding the probes together, until .000 appears on the screen.

If you dont have a calibration button ask your dealer for information

Isn't a .5 ohm high for leads testing? I always thought that .2 max but .1 was more expected.

 

[Lurch67]

My auto shop teacher said all flukes are calibrated free for life. You just need to pay shipping and get an RMA. Just give them a call and find out.

 

[diesel research]

It'll be close enough for most automotive type work.

it's hard to tell. while "1% off at battery voltage" is easy enough to justify, it's anyones guess once the voltages change or amps/milliamps/ohms function is selected.

Test equipment you cant trust, is worthless.

Practice on a bunch of different sensors and devices. 5v, ohms, ac, milliamps, etc. get a good overall idea if it will hold steady or not.

 

[signcrafter]

Thanks for the advice. I will see if I can find a calibration button but I don't think it has one.

So .14 volts off won't matter for most tests? Some things I've read about like batteries give a number for good/bad. Think I've read 12.65 or something for batteries. This won't really matter if the meter is off by .14 volts? What about things like parasitic draw tests were you need to measure small voltages across fuses, like in Stick's how to here, http://garagejournal.com/forum/showthread.php?t=133226. Will this mean the amps is off also? So measuring small amperage for parasitic draw won't be accurate?

 

[celticbhoy]

Thanks for the advice. I will see if I can find a calibration button but I don't think it has one.

So .14 volts off won't matter for most tests? Some things I've read about like batteries give a number for good/bad. Think I've read 12.65 or something for batteries. This won't really matter if the meter is off by .14 volts? What about things like parasitic draw tests were you need to measure small voltages across fuses, like in Stick's how to here, http://garagejournal.com/forum/showthread.php?t=133226. Will this mean the amps is off also? So measuring small amperage for parasitic draw won't be accurate?

Try it out. An open circuit voltage test with a faulty DVOM could be the difference of having a battery that is 75-50% charged, or 100-75% charged. Also, say the flukes test your battery at 12.3, but the BO is at 12.45 or 12.5, according to the flukes, you can't load test you battery because it can't hold a high enough charge, where as you may be wasting your time with the battery if the BP is giving a false reading of 12.45/12.5, thinking it can hold the charge.

 

[zkling]

Almost all meters can be calibrated. You need to remove the main board so you can access the trim pots. An external calibration button would be super dangerous. What you do is hook the meter up to a calibrated voltage supply and then adjust the trim pots till the meter reads exactly what the power supply is putting out.

Putting the leads together. Will only tell you if the meter accounts for the internal resistance of the lead wires.

Signcrafter, I actually have the calibration specs on that meter. When I talked to UEI today, they gave them to me

Go find yourself a calibrated voltage power supply. Then we can go from there. BTW UEI said calibration was $50. I think that meter is a .5% accuracy meter.

try this first

1. Turn the dial to the lowest Ohm seting
2. Touch the black ground point to the red lead point and look at the readout of the multimeter. If it reads 0-0.5 Ohms is a good multimeters.
3. If possible press the calibration button on the face of the multimeter, while still holding the probes together, until .000 appears on the screen.

If you dont have a calibration button ask your dealer for information

This is not a calibration, but rather a relative reading. It re zeros the resistance of the meter to account for different length leads.

 

[signcrafter]

try this first

1. Turn the dial to the lowest Ohm seting
2. Touch the black ground point to the red lead point and look at the readout of the multimeter. If it reads 0-0.5 Ohms is a good multimeters.
3. If possible press the calibration button on the face of the multimeter, while still holding the probes together, until .000 appears on the screen.

If you dont have a calibration button ask your dealer for information

It reads 0.1. I don't see any calibration button.

 

[zkling]

It reads 0.1. I don't see any calibration button.

What he is referring to is called the "Rel" button on your multimeter. It zeros out a reading so you can take a relative reading. When resistance is concerned you can touch the leads together, hit the "Rel" button and then the meter will read the true resistance of the circuit without adding in the resistance of the meter leads.

http://www.fluke.com/fluke/usen/com...iclecategories/dmms/low+ohms+measurements.htm

 

[gte718p]

Most likely your new meter is off. It might be the leads or even the connections.

I know nothing about the BP, but I would bet it is a standard import meter and probably not rated at better then 2% across the whole range. Even if you calibrate it it might not be right the next time you use it or may drift.
The proper way to calibrate it is with a calibrated bench source. You also need multiple points in the scale. On the high end meters there are multiple trim pots. By making it perfect at 12v you may pull it further off at 500v. I've never calibrated a cheap one so I don't know.

 

[signcrafter]

Almost all meters can be calibrated. You need to remove the main board so you can access the trim pots. An external calibration button would be super dangerous. What you do is hook the meter up to a calibrated voltage supply and then adjust the trim pots till the meter reads exactly what the power supply is putting out.

Putting the leads together. Will only tell you if the meter accounts for the internal resistance of the lead wires.

Signcrafter, I actually have the calibration specs on that meter. When I talked to UEI today, they gave them to me

Go find yourself a calibrated voltage power supply. Then we can go from there. BTW UEI said calibration was $50. I think that meter is a .5% accuracy meter.



This is not a calibration, but rather a relative reading. It re zeros the resistance of the meter to account for different length leads.

Seems to me that buying a calibrated voltage power supply would be pretty expensive. Guessing it would be cheaper to send it in for calibration. But if it's 50 bucks plus shipping for calibration and the newer version of this meter is only 137 bucks it doesn't really seem worth it to get this one calibrated.

I was planning on selling one or both of my flukes to offset the cost of this meter. Do you guys think this meter is alright being "off" like this or should I keep one of my flukes around for more accurate measurements? Or should I try to sell all 3 of my meters and look for a used fluke 87 or 88?

 

[devilsnight]

I'd look into getting one of the flukes calibrated, as stated I also believe it is free.. For me this wouldn't fly, 12.64 is indicating a fully charged battery, 12.5 does not. Depends on you though, I use my fluke daily to check battery voltages and charging systems.

 

[signcrafter]

I'd look into getting one of the flukes calibrated, as stated I also believe it is free.. For me this wouldn't fly, 12.64 is indicating a fully charged battery, 12.5 does not. Depends on you though, I use my fluke daily to check battery voltages and charging systems.

It's free to have flukes calibrated?

 

[zkling]

It's free to have flukes calibrated?

I am pretty sure it is not. I have a fluke 87V and a 27fm and they never offered to calibrate them for free Although I did buy them both used, so.

O I wasn't suggesting that you purchase a voltage standard, just saying that you can't calibrate off of a battery.

As for a reference standard. See if anyone you know or anyone in your town is into hamb radio. Usually those folks have a bunch of high end test equipment that would check your meters. Probably for the price of a few beers or the like. After that, do you know anyone that goes to college in a technical field, they have access to some top of the line stuff? Then finally see if there are any calibration labs in your town. They usually don't mind doing a basic cal for a few bucks for a home guy. Tell them you think the battery companies are shorting you on volts.

In regards to selling a meter. Of the 3 meters that you have I would keep the 77. That is a very respectable meter. If I was going to spend the money to get something calibrated that would be the one I would calibrate. It has the most accuracy potential of the bunch (0.3% IIRC). After that it depends on what you NEED.

I do not make my living working on cars, so I do not know what features would be useful to you. If you need the RPM and Dwell features of the BP, then I would keep that. However usually you can calculate RPM off of a frequency measurement. Then again that can be a time consuming process. It just depends on what you need to do with it. I will say it is very handy having 2 meters around at times for something like comparative voltage measurement or measuring voltage and amperage at the same time.

If you sold the 16 and the BP, then purchased an 87. You would have a heck of a meter combination between the 87 and the 77. Or even sell all 3 and purchase a 87 and an old 27fm.

 

[Roots]

It's free to have flukes calibrated?

No, they have a fee for calibration services. Fluke Calibration Services

I'm not sure what they charge, but I think Fluke used to charge an extra $100 for something to be calibrated, with certification/traceable records, when purchasing new.