January 1963 Popular Electronics
[Table of Contents]People old and young enjoy waxing nostalgic about
and learning some of the history of early electronics. Popular Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged.
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The early 1960s was
evidently a good time for printing quizzes in electronics magazines. Popular Electronics was no exception. As I
look through my collection I am finding quite a few. Here is the latest, from the January 1963 edition, that tests
basic knowledge of using analog multimeters (digital types were not around yet). I managed to get all the ones I
tried correct, but with question 9 I thought maybe it was a trick question, so I didn't bother venturing a guess.
Give it a try for yourself.
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QuizElectronic circuits perform functions similar to many mechanical devices and natural
phenomena, and finding an analogy between them often leads to a better understanding of both. See if you can match
the numbered electronic circuits on the left with the lettered sketches on the right.
Measurement Quiz Answers
1 TRUE. If a voltmeter is rated at 20,000 ohms-per-volt, it has an input
resistance of 100 times 20,000 ohms on its 100-volt scale, and 600 times 20,000 ohms on its 600-volt scale. The higher
this shunting resistance is, the less it reduces the resistance across which the voltage is measured.
If the instrument does not have a transit (shorting) position, set it on its highest current range-because the meter
will then be using its lowest value of shunt resistance. If the meter coil is jiggled while being moved, the voltage
it generates can produce the largest amount of damping current.
3 TRUE. Glass-and .especially plastic-meter
faces will have a static charge built up on them when they are rubbed with a dry cloth. The static charges will attract
the needle on the inside, and more dust on the outside. Use a cloth dampened with anti-static fluid (such as Weston's
4 FALSE. Use the highest current range because the ammeter pointer is least apt to "pin" against
a stop. Once the current magnitude has been determined, step down to lower current scales.
5 TRUE. Meter friction
due to worn bearings or dirt tends to make the needle stop too soon when it is slowing down for an indication.
6 FALSE. Most meters are of the D'Arsonval type, which responds to the average value of the signal waveform. An
a.c. meter scale increases this reading by a factor of 1.11 in order to indicate r.m.s. values of sine waves. For
a square wave, r.m.s. and average are the same; hence, the factor is not needed and the meter will read high.
7 TRUE. An ammeter deflects correctly when electrons enter its negative terminal and leave by its positive terminal.
8 TRUE. If the accuracy of a meter is given, for example, as 3 % of full scale deflection, it means that a
reading taken anywhere on that particular range is accurate to only 3% of the total range on that scale. Therefore,
if reading accuracy is what you want, select the smallest range that can indicate your reading.
9 FALSE. When
determining low resistances, don't measure the voltage drop across both the unknown resistance and the ammeter. The
ammeter resistance might be of the same magnitude or greater than the unknown resistance and introduce large errors.
10 TRUE. In selecting the highest voltage scale, you reduce the possibility of "pinning" the pointer against
a stop. Once the voltage magnitude is determined, step down to lower voltage scales.