"DoN. Nichols" wrote:

On 2011-03-17, Lewis Hartswick wrote:
Josepi wrote:

The guys used to laugh when I would get out the old AVO analogue needle
meter, with the mirrored scale, from time to time but the digital ones
(with all their so-called accuracy) would get confused in certain
applications.

Anyone who ever had to tune a circuit for a peak or a null
should be on the analog meter side of that discussion.
Those GD blinking digits, you cant tell if the reading
is going up or down.

Yes. Some of the digital multimeter, e.g. the Fluke ones which
I have, have a bargraph approximation of a needle. Not as much
resolution, but a fairly good guide until you get near the very fine
detail part of the job.

If you want to really be driven nuts by a digital, look at the
really old NLS (Non Linear Systems) DVMs. (From the late 1950s.) A
Kelvin-Varley divider, switched by a collection of (four) stepper
switches. One bank of each stepper illuminates a single lamp (of the
327 style) which illuminates the edge of a sheet of Lucite with a digit
engraved in it. This results in a single digit visible with a bunch of
invisible ones which are not illuminated. The stack of sheets is thick
enough so the different digits have a very visible depth offset.

When The voltage being measured is creeping up, there will be a
tick ... tick ... tick as it tracks. However, when the voltage is
creeping *down*, since the steppers can only move in one direction,
there is a brapp brapp brapp brapp as all four steppers reset to zero
position and then step up -- at about twenty steps per second, so there
is a several second delay before the divider again matches the input
voltage -- until it creeps down yet another step leading to another
series of brapps.

For tuning for a peak or a null, it is a nightmare. The case of
the thing is loaded with sound deadening foam rubber -- but when you
have one opened up to work on it, it is *very* noisy. :-)


HP made a DVM plugin for their 5245L counter that used 'end view'
Nixie tubes.

--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.