Fluke DMMs

[signcrafter]

That wouldn't cause them to be off that much, I don't think. Since I can't sleep, I calculated the max and min respective of their manufactures stated accuracy includin LSD error.

Meter Measured accuracy (VDC) High Low
fluke 16 12.44 0.9% +1 0.009 12.55 12.33 12.56 12.32
fluke 77 12.44 0.3% +1 0.003 12.48 12.40 12.49 12.39
fluke 87 12.67 0.05% +1 0.0005 12.68 12.66 12.69 12.65
BP 12.59 0.5%+1 0.005 12.65 12.53 12.66 12.52

So for a not so smart guy like myself what exactly do these numbers mean?

Here are some of my meters comparison. 2 Fluke, 4 HF, and 1 CM. Lowest (9.96 V) to highest (10.08 V) is about 1.2% difference. The 3 free HF meters did pretty well. They are all measuring the same 9V battery. All the meters are bought brand news and have very very little use except for the large HF meter in the background. That one has quite a bit of usage.

So yours are off .12 volts and all bought new and not used much, even your two flukes are different. Mine are a little more off at .23 volts. But mine were all bought used. Am I just being to **** about all this? Are all meters off a little if you don't get them calibrated every year or what ever the recommended time frame is? Should I just quit worrying and use them as is and everything will be fine? Is there ever a time in automotive work where .23 volts difference when measuring 12 volts will be an issue?

 

[oldtools]

Here's something else were not factoring in here: all these different meters's test leads and their varying levels of wear, resistance and build quality.

Here's a thought. Pick a set of leads and try them in every meter on a fixed DC voltage source. Say a 9 volt battery that's new or from a device that's been at rest for a while.

I'm trying to see if the different readings are the result of the test leads and not the meters at all.

Test lead can have an affect on the reading due to length of wire, quality of material, etc. Unfortunately, these test leads are not interchangeable.

 

[redwrench60]

Test lead can have an affect on the reading due to length of wire, quality of material, etc. Unfortunately, these test leads are not interchangeable.

I wonder if signcrafter could try with his. His meters (except the HF) should have interchangeable leads.

Around here this is what we call a redneck education, lol.

 

[zkling]

Here's something else were not factoring in here: all these different meters's test leads and their varying levels of wear, resistance and build quality.

Here's a thought. Pick a set of leads and try them in every meter on a fixed DC voltage source. Say a 9 volt battery that's new or from a device that's been at rest for a while.

I suggested that way back. It must have fallen on deaf ears.

Try using the same leads in each meter. Then see if they still give different readings. Also try both auto and manual ranging modes on each meter, see if the readings are different.

Test lead can have an affect on the reading due to length of wire, quality of material, etc.

Again first page, I doubt if they could account for that much variance in readings though.

Unfortunately, these test leads are not interchangeable.

On decent meters the test leads should be interchangeable, especially between the 3 flukes. Even the BP he has should have the same recepticals for V and com. I forget what the name for it is, but they are a standard.

Am I just being to **** about all this?

Yes and no, but you are just wasting time and money going around in circles with this, SO..... your choice. Were you able yo do work before yo bought the BP and the 87? Probably, now with the addition of two more meters, you question the accuracy of all your meters. The 77 is a respectable meter. I will say again, again a measuring tool that is not calibrated is useless.

Here are your two choices

1.) Live with it and go on with your life.

2.) Find someone that has a known accurate meter and check yours against theirs. If you could find 2 other people with a good condition 87, and the reading of yours matches theirs, I bet your 87 is on. If you 77 matches the reading of their 87 then the 77 is on. Without comparing it to something known you are just shooting in the dark.

So for a not so smart guy like myself what exactly do these numbers mean?

Multimeter accuracy is given as a % of the reading ± the lest significant digit of the reading in question.

Good explanation

http://www.designworldonline.com/how-to-determine-digital-multimeter-accuracy/#_

What I calculated was the range the value COULD be based on the accuracy of the meter you used. Basically the range of what the REAL value of the battery is.

Meter High Low
fluke 16 12.56 12.32
fluke 77 12.49 12.39
fluke 87 12.69 12.65
BP 12.66 12.52

As we can see there is not much overlap. The 87 has the lowest window, because it has the highest accuracy of all the meters tested. Likewise the 16 has the largest windows because it has the lowest (0.9%) accuracy of the meters tested. The 77 falls withing the window of the 16, which it should since it has 3x the accuracy of the 16. The outlyers are the 87 and BP, they don't really overlap except at the top end of the BP and the bottom end of the fluke. If everything was perfect the readings should be something like

fluke 16 low
BP low
fluke 77 low
fluke 87 low
fluke 87 high
fluke 77 high
BP high
fluke 16 high

Here is what I would do, but it is your decision.

Get a brand new 9v batter. Pick the best condition test leads you have. Use the same battery and test leads in all meters and measure your car battery again. Check the fuses in all meters, check both manual and auto ranging mode. When taking the reading, make sure you have good contact and the reading is stable on the display and not fluctuating. Post the results and see what you get again.

 

[signcrafter]

I suggested that way back. It must have fallen on deaf ears.

Again first page, I doubt if they could account for that much variance in readings though.

On decent meters the test leads should be interchangeable, especially between the 3 flukes. Even the BP he has should have the same recepticals for V and com. I forget what the name for it is, but they are a standard.

Yes and no, but you are just wasting time and money going around in circles with this, SO..... your choice. Were you able yo do work before yo bought the BP and the 87? Probably, now with the addition of two more meters, you question the accuracy of all your meters. The 77 is a respectable meter. I will say again, again a measuring tool that is not calibrated is useless.

Here are your two choices

1.) Live with it and go on with your life.

2.) Find someone that has a known accurate meter and check yours against theirs. If you could find 2 other people with a good condition 87, and the reading of yours matches theirs, I bet your 87 is on. If you 77 matches the reading of their 87 then the 77 is on. Without comparing it to something known you are just shooting in the dark.

Multimeter accuracy is given as a % of the reading ± the lest significant digit of the reading in question.

Good explanation

http://www.designworldonline.com/how-to-determine-digital-multimeter-accuracy/#_

What I calculated was the range the value COULD be based on the accuracy of the meter you used. Basically the range of what the REAL value of the battery is.

Meter High Low
fluke 16 12.56 12.32
fluke 77 12.49 12.39
fluke 87 12.69 12.65
BP 12.66 12.52

As we can see there is not much overlap. The 87 has the lowest window, because it has the highest accuracy of all the meters tested. Likewise the 16 has the largest windows because it has the lowest (0.9%) accuracy of the meters tested. The 77 falls withing the window of the 16, which it should since it has 3x the accuracy of the 16. The outlyers are the 87 and BP, they don't really overlap except at the top end of the BP and the bottom end of the fluke. If everything was perfect the readings should be something like

fluke 16 low
BP low
fluke 77 low
fluke 87 low
fluke 87 high
fluke 77 high
BP high
fluke 16 high

Here is what I would do, but it is your decision.

Get a brand new 9v batter. Pick the best condition test leads you have. Use the same battery and test leads in all meters and measure your car battery again. Check the fuses in all meters, check both manual and auto ranging mode. When taking the reading, make sure you have good contact and the reading is stable on the display and not fluctuating. Post the results and see what you get again.

Trust me I appreciate all your's and everyone else's advice and help and nothing is falling on deaf ears. I will pick up some new 9V batteries and do what you said and report back.

 

[richfinn]

Trust me I appreciate all your's and everyone else's advice and help and nothing is falling on deaf ears. I will pick up some new 9V batteries and do what you said and report back.

9v battery (it's not a calibrated voltage)

Try the 5v sensor ref voltage test I suggested on the first page

It's 5v exactly

Job done

 

[zkling]

If your using it to fix cars I would live with it, does it go to 0.00v when set to DC volts if you touch the probes together?

What ohms reading do you get when you touch the probes together?

Don't forget it's true RMS on AC (so you may get a small difference anyway compared to your other meters).

None of this has anything to do with the accuracy of a meter. NONE, ZIP, ZILCH, NADA.

Touching the probes together is not going to verify a measured voltage somewhere else in the scale.

The Ohms reading is going to tell you the internal resistance of the leads. Will change depending on lead length.

RMS has nothing to do with DC voltage. I am pretty sure all of those meters are true RMS as well, but that is besides the point.

If you disconnect a coolant temp sensor on almost any car and measure the ref voltage you should have exactly 5v with the ignition switched on if you need a quick calibration check.

Try the other tests I mentioned particularly the 0.00v DC check

If it passes these 3 tests its fine for diagnosing vehicles.

Using that to try and check the accuracy of a 0.05% DC meter is like using a tape measure to calibrate a micrometer. Useless measurement and poor idea.

9v battery (it's not a calibrated voltage)
Try the 5v sensor ref voltage test I suggested on the first page
It's 5v exactly
Job done

Read again. He is not measuring the batteries themselves. He is making sure the battery in the meter is good, that way the playing field is level. There is only one way to check which one of those meters is accurate. Apparently the OP doesn't want to do the proper way.

A multimeter and a welder, two very dangers tools in the hands of an uninformed operator.

 

[richfinn]

Wow what guy all that talent and knowledge (that you copied out of the brochure)

**** off *****

 

[redwrench60]

Good lord...........

 

[zkling]

*****

Yea, I'm the *****, yet I actually post useful information. Not the same can be said about your posts now can they.

that you copied out of the brochure

Actually that knowledge I referred to is based upon years of experience both reading and hands on. Maybe if you did a bit of reading yourself you too could become more knowledgeable about multimeters.

 

[signcrafter]

Sure seems to be a lot of posts that are going to **** lately. It's been a good discussion so far and would **** to get the thread locked over some argument.

Guys, I appreciate all the help and advice everyone has shared. I've learned a lot during this adventure thanks to you all.

I'm just a DIYer, and in truth any of these meters would probably be just fine for anything I come across. I would like to figure out which one is right but looks like that isn't going to happen without spending more money. I will most likely just use these for now and look into selling them all and buying a new fluke down the road. Not sure yet.

 

[redwrench60]

Dude. Back it off a notch. It's not a contest. You're coming off as a tool. We're all just having a conversation and trying to learn something.

 

[richfinn]

Yea, I'm the *****, yet I actually post useful information. Not the same can be said about your posts now can they.



Actually that knowledge I referred to is based upon years of experience both reading and hands on. Maybe if you did a bit of reading yourself you too could become more knowledgeable about multimeters.

Which bit was useful, reads like a load of horseshit to me with no actual substance.

1. Touch the probes together and see if meter reads 0.00v

Useful if your volt dropping fuses to check for current flow and you want accuracy in the Mv range

2. Touch probes and check ohms

Good test to check resistance of leads

3. Use 5v sensor ref voltage to compare all meters and see which is most accurate

The only verifiable calibrated voltage test suggested in the whole thread


Your suggestion is basically change the battery and look I can do math

*****

 

[richfinn]

To the OP, don't over think it. It's not as complex as some posters want you to believe.