EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: hussamaldean on December 03, 2018, 12:49:00 pm
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Hi all,
I have couple of stupid questions regarding the multimeters
First question
in cheap multimeter (in general) 9V battery is used while in professional one such as gossen uses 2X 1.5V, why ?
the other one
why there is no AC current in cheap 5$ multimeter ? only DC
I know they sound stupid but I am curious to know why
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Cheap multi-meters target infrequent users. 9V batteries run down faster but make other internal circuitry easier. AC Current measurement requires careful design and more expensive construction to be safe.
Measuring AC current, even in moderately priced meters requires special precautions such as limiting the time of the test.
All features are not equal in cost to implement.
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9V batteries are also used in some expensive meters, it is compact and secures a stable voltage to the internal electronic because a voltage regulator is used.
With two AA/AAA batteries there is not voltage enough for a regulator and the electronic must work over a wider range of voltage, some chips can easily do that, other cannot.
With 3 or more AA/AAA cells there usual is enough voltage for a regulator, but it is not as compact.
The meter without AC current will often lack low voltage AC measurement as well, this is because the rectification is a single diode, not a rectification circuit and a single diode has way to large voltage drop to be used for a current shunt.
I have tested many multimeters (including tear-down) and also written a few articles about using them, maybe you can find something useful there: https://lygte-info.dk/info/indexDMMReviews%20UK.html
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First question
in cheap multimeter (in general) 9V battery is used while in professional one such as gossen uses 2X 1.5V, why ?
Makes it cheaper to manufacture.
(it's more expensive to use but they don't care about that)
why there is no AC current in cheap 5$ multimeter ? only DC
Because hardly anybody wants it and they save the cost of a few more components that way.
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thx for the help not making jocks about my questions :D