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Old 2nd June 2005, 05:44 PM   #11
Kermit is offline Kermit  Norway
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I happen to have two different multimeters, one really cheap one and a more expensive one.
When measuring a 6V DC supply the cheap multimeter measures 13V when set to measure AC and the more expensive one measures 0,01V when set to AC.
None of the multimeters are true RMS as far as i know....
So I guess the answer lies in the price tag on your multimeter
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Old 2nd June 2005, 05:52 PM   #12
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Default Re: not too fast

Quote:
Originally posted by raif
I measure dc voltage with multimeter set to dc. The problem is when I check ac voltage across output terminals( obviously, multimeter set to ac) it shows 70 volts ac!

thanks

This is normal for some cheap multimeters. An AC sine voltage of 70V would have an average values of something in the area of your 37V. Since such a cheap meter is average responding, it is calibrated to show 70V whenever it gets 37V average on AC scale. And of course those 37V DC ARE 37V average to that meter.

Use a series cap to the meter, that will allow you to read the AC ripple.

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Old 2nd June 2005, 07:36 PM   #13
cowanrg is offline cowanrg  United States
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I have a true RMS meter, and i have on several occassions had it mistakenly set to AC instead of DC, and sure enough, it measures the slight ac ripple. its very low, so it has confused me at first until i realize its on ac instead of dc. my other cheap meter just measures some wrong value, not the ripple.
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Old 3rd June 2005, 10:14 AM   #14
raif is offline raif  Turkey
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Default caltek cm1200t

Thanks everyone the culprit is the cheap multimeter. Any suggestions for a decent one which will also measure inductance.

Thanks
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Old 3rd June 2005, 10:50 AM   #15
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Well, you learn something new every day! 'Cos I've got a scope it's something I never bothered to check, now I'll have to go through all my DMMs and see if any work that way.
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Old 3rd June 2005, 11:10 AM   #16
Magura is offline Magura  Denmark
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Default Re: caltek cm1200t

Quote:
Originally posted by raif
Thanks everyone the culprit is the cheap multimeter. Any suggestions for a decent one which will also measure inductance.

Thanks

AFAIK there is only one meter that is worth buying that fits your needs. Fluke 110.

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