I've had various multimeters over the years; the last two have a
frequency counter setting, which might sometimes come in useful - if I
knew how to use it :-)
The manual for the current one is no help. Is there some kind of standard
for what signal they're expecting?
On Fri, 27 Aug 2010 11:18:44 -0700, jamesgangnc wrote:
No... not sure if I should risk it. Maybe it expects a sine wave, or a
square wave, and maybe positive and negative, or maybe only positive
relative to 0, and maybe the upper (and/or lower) limits are quite low
(or even fixed at some narrow range...
On the one hand, maybe it'll be perfectly happy with a 200V p-p sine
wave; on the other maybe it's only expecting a +5V square wave, and
anything else will make it go bang :-)
(particularly useful right now would be if I could use it to measure the
lawn tractor engine's rpm, so I could set the idle correctly and check
that it's not running too fast with the throttle wide open) - I'm not
sure what bits I've got in the junk box that I could use for a sensor,
General-duty multimeters will expect AC in the input range of the
multimeter. Certainly the specifications portion of the manual will
tell you the range you can expect.
It should also say whether it is "true-rms" or not--better meters such
as the Fluke or even some of the imports have internal circuitry/logic
that does some cleanup of distortion/clipped signals that affects not
only the displayed rms values but the frequency as well.
The question in the other subthread is "no"; it won't go "boom" unless
you connect to something that would make the meter go boom on the VAC
scale -- connecting in series would undoubtedly blow the input
protection fuse; whether it would be permanent damage would depend on
what was connected to and the meter design.
But, the other portion is that they are _not_ logic analyzers unless
have a specific feature other than AC frequency. You could undoubtedly
build a shaping circuit and make it work to measure the timing (that's
all a timing meter really is) but it won't work just as is for the purpose.
Might help if you told us exactly which meter you have, as they are all
different. You might also consider asking the manufacturer.
Harbor Freight sells one for $25, and they state in the manual that,
"Reading is possible at input voltages above 10Vrms, but the accuracy is not
guaranteed." This suggests that is expecting standard TTL/CMOS logic
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.