At 02:51 8/27/99 -0700, Coby Smolens wrote:
>I'm gonna check this in the literature tomorrow - I seem to remember that
>although the readings you see on-screen on a good DMM, whether numerical
>output or simulated analog (the little bar graph thingy that approximates a
>moving needle) are "averaged", the min-max feature works differently. Since
>it doesn't have to produce real-time displays it records actual minimum and
>maximum readings and holds them in memory until one requests them. Thus, if
>the V. drops to zero, even for a thousandth of a second, that fact will be
>captured by the machine. Or have I been bamboozled?

Back when I was building these things (before the bar-graph thingy
appeared) they used a technique called "dual-slope integration" where they
use the input signal to charge a capacitor for a specified time, then
measure the time it takes to discharge it at a constant rate and display
the count as (voltage, pressure, weight, whatever).  The display processing
itself was essentially instant, but it only got data to display every
couple seconds.  With that technique there is no such thing as an instant
measurement.  But they may be doing it differently now...

david
David Beierl - Providence, RI
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"