# Why do multimeters show values at the lower parts of a given range the way they do?

Suppose I have a 20,000 counts multimeter, and I am measuring a 220k resistance with it.

The multimeter can only display a resistance below 200k as 200.00k - supposedly because of the counts. For higher resistances, it has to switch the range and starts displaying the result as 0.2200M. But this makes no sense to me: switching range doesn't require the display to change in a major way like that.

Granted, by switching range the meter loses one digit of precision, and conjuring it up would be wrong. But why not simply hide that non-existent digit, and display 220.0 k (see how the last digit is missing) instead of the less readable 0.2200M - they both have the exact same precision!

Why don't multimeters do this seemingly very sane thing, not even the very expensive ones? Am I missing something important?

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 Someone I asked in person suggested that since 220.0 k and 0.2200M are exactly the same thing, this might just be because nobody cares. If you don't care, that would be a helpful answer too :) – romkyns Apr 30 '11 at 14:33

The display is not the limiting factor (as you point out). Fundamentally, there is a cut-off. If the display was the most expensive part in the meter, then most meters would probably read up to 9999 on all digits. However, there's a couple factors that make the meter ranges what they are.

There is a limit to how high a range goes - the count is a design decision for the meter maker. A 20... meter isn't the only type available either, I personally have a 6000 count meter.

Logarithmically, you get the most bang for your buck by having 2000 counts. See the image of the number line below. By doubling the counts from 1000 to 2000, you get a bigger bang for your buck, and you also get to use one more digit (better for marketing).

There's another reason for not dropping the least significant digit. Part of the gotcha with auto-ranging meters is that you can easily forget that the meter has different measurement ranges, and that the measurement accuracy changes with each range. For example, compare the following displays:

193.00 k
.1930 M
193.0  k <----- Would you notice the missing digit as easily?


Personally, I see it as a more obvious way of conveying information about the measurement. It doesn't detract much from the readability in my opinion.

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 Even though I disagree on what's more readable and in which reading the precision is more obvious, your answer points out that it is indeed more subjective than I thought. Thanks! – romkyns May 2 '11 at 8:28