In the chapter on Ohmmeters (8.6), it is repeatedly said that the
scale on an ohmmeter is logarithmic and, in particular, there is the
statement
"With a logarithmic scale, the amount of resistance spanned for
any given distance on the scale increases as the scale progresses
toward infinity, making infinity an attainable goal."
This is not correct --- per Ohm's law, the scale on an ohmmeter
varies as the reciprocal of the current, not as its logarithm. Whilst
the reciprocal of zero is infinity, the logarithm of no finite number
is infinity so infinity is not attainable with a logarithmic scale
although it is attainable with a reciprocal scale.
Call me a mathematical stickler, but this sloppiness sticks out at
me like a sore thumb when I read this otherwise excellent
exposition --- one does not make an ohmmeter by pasting a slide
ruler on an ammeter movement Please consider changing the
terminology so as to fix this inaccuracy.
scale on an ohmmeter is logarithmic and, in particular, there is the
statement
"With a logarithmic scale, the amount of resistance spanned for
any given distance on the scale increases as the scale progresses
toward infinity, making infinity an attainable goal."
This is not correct --- per Ohm's law, the scale on an ohmmeter
varies as the reciprocal of the current, not as its logarithm. Whilst
the reciprocal of zero is infinity, the logarithm of no finite number
is infinity so infinity is not attainable with a logarithmic scale
although it is attainable with a reciprocal scale.
Call me a mathematical stickler, but this sloppiness sticks out at
me like a sore thumb when I read this otherwise excellent
exposition --- one does not make an ohmmeter by pasting a slide
ruler on an ammeter movement Please consider changing the
terminology so as to fix this inaccuracy.