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I am a software developer trying to understand how computers work at a lower level.

I have purchased a digital MultiMeter. I realise that MultiMeters enable you to measure voltages, ohms, amps etc. I also understand that you can select a range e.g. 20k ohms by turning the knob. If I select 20k ohms for example, then does this mean that the MultiMeter can then be used to measure up to 20k ohms of resistance? and if I select 20V of direct current then does this mean that the MultiMeter can be used to measure up to 20V of direct current?

I have a book which comprehensively talks about MultiMeters but does not confirm this question I have.

I realise it is a basic question, but then I am new to this field (I hold a GCSE in Electronics).

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A 20V scale would let you measure up to 20 volts in a circuit. You would use an 20A scale to measure up to 20 amps through a wire or component. –  Michael Karas Dec 17 '12 at 22:32
    
Can you tell us the model number of the multimeter or at least post a picture? \$ 200 \mbox{ }m \Omega\$ sounds a bit strange on a meter that has manual ranges unless it's a very old meter. –  AndrejaKo Dec 18 '12 at 1:17
    
@AndrejaKo, it is a Sinometer MS8230B Digital Multimeter. –  w0051977 Dec 18 '12 at 12:37
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3 Answers

You should check the manual that came with your multimeter. However, in general, digital multimeters display a 1 on resistance ranges to show overranging. That means that the resistance connected to the meter is larger than the meter can display on whatever range setting it is on. If the meter is not connected to anything, then the resistance is very high and it will display a 1 on all ranges. Are you sure the 200m range is a resistance range and not a voltage or current range? If it is a resistance range and the leads are shorted then 00.0 would be the expected reading. If the leads are not shorted than something is not right. On the other hand, if the 200m range is a voltage (200 millivolts maybe) or current range (200 milliamperes maybe), and nothing is connected, 00.0 is the correct display.

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I have one that says "OUCH" when it is overranging –  NickHalden Jan 16 '13 at 23:10
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Yes, it is that simple. In general you wish to use the smallest range you can. For example if you are on the 20 k range and it shows around 1 k ohms, change down to the 2 k range.

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Thanks. If I select 2K, 20K, 200k or 2M ohms the digital display says 1. If I select 200m, it says 00.0. Is there a simple explanation for this? –  w0051977 Dec 17 '12 at 21:12
    
When it says "1" (sometimes "OL") it means that the measured value is out of range. If you set any range for resistance measurement and measure anything, ie you don't connect any resistor to the test leads, the result will be out of range for sure. I'm not sure about the zeroes @ 200m... are these milliohms or megaohms? –  Vladimir Cravero Dec 17 '12 at 21:42
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It is Milliohms. –  w0051977 Dec 17 '12 at 21:47
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Now this is strange. Check the manual as Barry said and report back to us then. –  Vladimir Cravero Dec 17 '12 at 22:36
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How about changing the mode from Manual to Auto? That solves the problem most of the times.

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