| MadSci Network: Physics |
Hi--
Very good questions.
To answer your second question first, wikipedia (www.wikipedia.org) has a good write up in English and, from what I can tell, in German as well.
But the basic approach is that a multimeter works by comparing the input voltage (what you want to measure) with a reference (generated by a power supply which may be a battery but usually is not). If the input voltage is *higher* than the reference voltage, a circuit called a voltage divider (which consists of two resistors and can be 0.001% or better accurate) is used on the input voltage to *reduce* it to some value less than the reference and then the two voltages are compared. If the multimeter is used to measure *resistance*, then a current is forced through the unknown, generating a voltage, and we proceed as before.
To answer your first question, which I translate as "How do you measure
the resistance of a voltage source, such as a battery," it's quite easy
but my artwork skills are not up to the job and I need to make a couple
of drawings to demonstrate the principle, as well as that of the voltage
divider. So if you will give me a snail-mail address, I'll be happy to
send you that answer.
Regards,
Barry
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