Hi Virgil,
As to the quoted post below, here's a few quick and dirty opinions [found below the quoted section]:
Originally posted by sparky66wv:
Speaking of questions....
What does an analog meter display, RMS or averaged?
Would it be considered more or less accurate, assuming being recently calibrated?
My old boss swore that the real-time movement of the needle would tell you infinitely more that a 1/2 second digital sample. Any truth to this?
Why not use a "digilog" meter?
Q1: What does an analog meter display, RMS or averaged?
A1: Depending on the type and quality of the meter, you would find both levels in Analog scale meters.
The straight Voltage meters would definitely display an Effective [RMS] voltage value - since that closely resembles the DC equivalent in a Power formula. This would be common for simple meters and high end ones.
For Amperage, the high end ones will likely be the only ones that will readout RMS levels of more than the fundamental Hz. It's not very simple to do the math involving multi Hz, then dump it into a coil with a moving armature.
By contrast, the normal common AC ammeter with an Analog scale will describe an Averaged current level - it finds some common place within the distorted sinewave and registers that value. These also view the current primarily at 60 Hz, so accuracy of total current flow is far from exact.
Q2: Would it be considered more or less accurate, assuming being recently calibrated?
A2: Normally, the Analog scales will have 5% - 10% tolerance, where as the simplest Digital scale will have 1% tolerance.
Analog tolerances are effected by lots of factors, which change from location to location, plus their loading effects [input Impedance] varies, due to the coil/armature stuff; however, a Digital device has very steady state logic gates for inputs.
There are high end Analog scale meters with better than 1% tolerance, but they cost $$$!
One way to clamp some accuracy to an Analog scale is by using either a trimpot, fixed "Hi Q" resistor[s], Thermistor, or a Varistor.
Q3: My old boss swore that the real-time movement of the needle would tell you infinitely more that a 1/2 second digital sample. Any truth to this?
A3: Using an Analog scale will describe swinging fluctuations on circuits as they occur and with a visual indication - where a Digital scale just cannot even come close to being as simple to detect. The fluctuations on a circuit will directly correspond with the Analog meter's armature [needle], so when something changes electrically, the needle swings.
I have seen some high refresh rate [quick sample and hold] Digital meters, but they are still not as "simple to the eyes" as an Analog scale has for fluctuations.
Q4: Why not use a "digilog" meter?
A4: I have seen some in different designs - Voltage, Amperage and Multi Meters, but they were high end ones. Not sure if any low to medium end ones exsist.
Scott SET
