Hi Peter,
Sometimes, on an instrument that has been in storage for a long
while, corrosion on the input BNC/N connector can cause for a round
of strange readings... non-linear junctions, and all that.
Be sure that the BNC's on the cables, and on the instrument are
clean and lubed with a little cramolin, or other contact cleaner.
-Chuck Harris
Peter Gottlieb wrote:
toggle quoted message
Show quoted text
So I'm finally getting to unpack all my gear and set up a lab again. As part of
setting up my bench I am doing basic functionality checks on the instruments I
intend to use. One is a "straightforward" HP 5335A counter. Hooked it up to a
HP signal generator putting out a nice 5 volt sine wave at 1000 Hz. What does
the counter tell me? Around 1800 Hz and unsteady. Analog scope tells me it
looks great, nice and clean... Try it again on the counter and 1000 Hz on the
nose and rock solid. I've found in the past that it is very easy to get the
second harmonic reading on a counter as well. And DVMs, forget about it, some
read AC riding on DC very strangely, or if you have a non-true-RMS meter...
There are many cases where you need to understand what you are looking at and
what you are expecting. You need this to sanity-check the instrument as well as
to understand what you need to do to verify your reading. Yes, analog scopes
can show you a very true picture of what's happening but you can easily miss
some massive fast/short transients too.
To get the most from this gear you need to understand each instrument and what
it's limitations are. You need to know your tools.
Now what's up with that 5335A and the strange result I am now unable to
duplicate? ;-)
Now back to work...
