I'm considering the purchase of a new Fluke DMM. I like the
> low-impedance feature of the 117, but the low-pass filter feature of
> the 87 is also attractive.
>
> I had a conversation with a support engineer at Fluke today to try to
> help me decide between these two meters.
>
> It came down to the question of whether the variable-frequency drives
> I come across will have noisy outputs which the low-pass filter will
> be helpful in dealing with.
>
> Among other services, I install some (3-phase, mostly) VFDs for 230v
> motors on old printing equipment to give them a 2nd life.
>
> I have no idea how many (ie, percentage) of VFDs are "noisy" that
> will make measurement difficult with a DMM w/o low-pass filtering. Is
> this a common problem?
>
> If you've got some experience in this area I'd like to hear your
> comments.
>
> Thanks,
> Dave
The Fluke 289 has both a low pass filter and LowZ input impedance. But you get the annoyance of the short battery life and graphical display.
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Check out the new Fluke 28-II rugged meter, it also has the filter, but no lowZ:
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Quote: "Unique function for accurate voltage and frequency measurements on adjustable speed motor drives and other electrically noisy equipment (28 II)" but that is just the normal low pass filter feature.
Dave.