Noob multimeter question 2

[timeline1968]

I'm going to pre-apologize for this question, as it's pretty simple:

I have a multimeter that I'm trying to figure out what the accuracy is when measuring small values of ohms (.5-10ohms). The booklet for the meter states:

Range:500.00ohms, Resolution: 0.01 ohms, Accuracy 0.05%+10^3

I don't understand the last part of the accuracy reading. The 0.05% I understand (say 20ohms: 20*.0005 = 0.01ohm, so I could read 19.99 to 20.01) but what does the 10^3 mean?

Thanks for any assistance.

 

[IRstuff]

Can you look at a datasheet from the same manufacturer to get a better description?

Offhand, it looks to be a typo, since most such specifications are usually a percentage, which represents a scaling error, and the measurement noise, which is usually given as "counts."

So, it would normally read "0.05% +/- 3 counts," or something to that effect.

TTFN

FAQ731-376

 

[timeline1968]

This is for a Fluke Multimeter. They state that its accuracy is supposed to be represented as:

+/-([% of reading] + [number of least significant digits])

Isn't 10^3 = 10,000? I don't understand at all. Maybe it is a typo...

 

[timeline1968]

On their website the accuracy is listed as:

Accuracy ± (0.05%+2)

The 2 means 2 LSD, so is it accurate to 0.1 ohm then since the range is listed as 500.00?

 

[IRstuff]

Are you sure you're not confusing the superscripted number with a reference to a note?

The Fluke Series 80 manual uses forms like +/-(1.0% + 3)[sup]2[/sup] where the superscripted 2 refers to Note 2 at the bottom of the table.

http://assets.fluke.com/manuals/80v_____umeng0100.pdf

TTFN

FAQ731-376

 

[logbook]

>On their website the accuracy is listed as:
>Accuracy ± (0.05%+2)
>The 2 means 2 LSD, so is it accurate to 0.1 ohm then since the range is listed as 500.00?

The accuracy depends on the reading.
Let's work through it.
Suppose you are measuring roughly 500 ohms.
0.05% of the reading is 0.25 ohms.
2 LSDs is 0.02 ohms.
The accuracy is ±(0.25 + 0.02) = ±0.27 ohms.

If you are measuring only 50 ohms on this same scale the error is then ±(0.025 + 0.02) = ±0.05 ohms

 

[timeline1968]

IRStuff: OMG, I am a frikin' tard. The 3 is a reference to a note below that states: Using relative mode (REL delta) to zero residual reading). I was stuck looking at it as engineering notation.

This does not, however resolve everything as the specs seem to be conflicting. The book says 10 LSD and the web says 2 LSD.

Logbook: Thanks for the example, it makes the computation completely clear, but I still have the problem with the two listed specs not matching now.

 

[itsmoked]

Fluke using superscripted numbers and parentheses to indicate notes. THAT! is truly lame.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[IRstuff]

Which meter is it?

Generally, the stuff on web pages tend to be the BEST possible performance, while the actual manual lists all possible configurations. You'd need to identify the particular model, the webpage, and a link to the manual for us to get any further insight into the problem.

TTFN

FAQ731-376

 

[timeline1968]

It's a 189 True-rms multimeter listed on their website here:

http://us.fluke.com/usen/products/F...FlukeUnitedStates&category=HMA(FlukeProducts)

 

[IRstuff]

OK, but their caveat, i.e., the asterisk says "Accuracies are best accuracies for each function" on the summary spec page here:

http://us.fluke.com/usen/products/s...64(FlukeProducts)&category=HMA(FlukeProducts)

The extended spec:

http://assets.fluke.com/datasheets/2153ExtSpecs.pdf

shows that 3 of the 8 ranges has that accuracy, but they're not the particular range that you're interested in.

Everything seems consistent to me.

TTFN

FAQ731-376

 

[Skogsgurra]

That's really helpful, IR. PLS for you.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[timeline1968]

Thank you IRstuff. I get it now.