Digital Multimeter range question

[RichTes]

Why does an auto ranging digital multimeter have ranges? What's the point?

I can see on an analog meter knowing which band the result is on, but for an auto ranging digital meter if it shows 120.0 why do I care that it might be in a 0-600v range versus showing OL in a 0-60.

Thanks.

 

[Cruzan80]

Resolved level of detail. A 0-600V range is less precise than a 0-60V range, so the ending digit is not as accurate.

 

[johnre]

Ultimately, the measured parameter ends up at a finite resolution A/D converter. It's best to use as close to the full range of the A/D input as possible, in order to optimize for the resolved level of detail that @Cruzan80 spoke of above. So that means designing it with several ranges, often in a half-decade logarithmic arrangement of 3 / 10 / 30 / 100 etc.

The analogy you used of an analog meter is actually a pretty good one here; you wouldn't use an analog meter over only the bottom 5% of the needle's arc for the same reason you wouldn't do this with and A/D converter - ability to resolve small readings.

And this all has nothing to do with whether the DVM is manual or autoranging - it's the same problem regardless.

 

[wyliesdiesels]

has to do with the electronics, accuracy and resolution. its not as dumb as you may think

 

[kbeefy]

The difference between infinity and 1 ohm is huge.

 

[PCustoms]

The difference between infinity and 1 ohm is huge.

How huge?

 

[Innovate1]

How huge?

Infinite. Infinity - 1 = infinity.

 

[PCustoms]

Infinite. Infinity - 1 = infinity.

 

[Chuckster in NJ]

 

[toplessHO]

is this like the one armed fisherman?
showed how big the fish he caught was by holding his hand out

 

[fitter30]

One is just checking voltage to see if its hot another if your trying to set to something up and want to be as close as possible.