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From: notme on 11 Nov 2009 03:11
Fluke clamp current meters have 2 features that seem similar: peak and
in-rush. The older models have Max (some: Peak). The recent advent in Fluke
clamps is "In-rush".

How do these differ? Isn't in-rush current the short, max current at
motor-turn on? Shouldn't meters with a Max feature capture this accurately?

Compare, for example, my old Fluke 36 (Max):

<http://assets.fluke.com/manuals/36______iseng0000.pdf>

and the 334 (In-Rush):

<http://us.fluke.com/VirtualDemos/330shock.asp>

(click "Explore" then "Selection Guide").

How do Max & In-rush differ? Only in the marketing department?
Or is there a real-world difference?

Thanks,
Dave

From: notme on 11 Nov 2009 03:18
I found this description on the Fluke 33x virtual demo page:

"Note: In-rush current measurements done with a 330 Series Clamp Meter will
differ from Min/MAX, Peak, or Peak-Hold measurements which are not triggered
events."

Sounds like other than auto-triggering, the results are the same.

Dave

From: Salmon Egg on 11 Nov 2009 08:10
In article
<0001HW.C71FB1C00028C68CB08A39AF(a)news.eternal-september.org>,
notme <notme(a)notme.org> wrote:

> Fluke clamp current meters have 2 features that seem similar: peak and
> in-rush. The older models have Max (some: Peak). The recent advent in Fluke
> clamps is "In-rush".
>
> How do these differ? Isn't in-rush current the short, max current at
> motor-turn on? Shouldn't meters with a Max feature capture this accurately?
>
> Compare, for example, my old Fluke 36 (Max):
>
> <http://assets.fluke.com/manuals/36______iseng0000.pdf>
>
> and the 334 (In-Rush):
>
> <http://us.fluke.com/VirtualDemos/330shock.asp>
>
> (click "Explore" then "Selection Guide").
>
> How do Max & In-rush differ? Only in the marketing department?
> Or is there a real-world difference?
>
> Thanks,
> Dave

The essence of one of these meters is a current transformer using a core
that can be opened and then closed. In the closed condition, the
magnetic reluctance of the core is made as small as possible. The
secondary coil is connected to a small resistance. The idea is to have
the current flow waveform in the secondary duplicate the current flow in
the often single turn primary. The voltage on the resistor than
duplicates the current waveform.

How this secondary waveform is used and processed will determine the
features of the meter. Fluke is one of the big names in hand held
oscilloscopes. It is possible to digitize the start of this waveform.
Then various algorithms can be used to characterize the waveform
including the start of it.

Bill

--
As the years go by, dying just before having to fill out a tax return has merit.
From: PeterD on 11 Nov 2009 08:36
On Wed, 11 Nov 2009 00:18:20 -0800, notme <notme(a)notme.org> wrote:

>I found this description on the Fluke 33x virtual demo page:
>
>"Note: In-rush current measurements done with a 330 Series Clamp Meter will
>differ from Min/MAX, Peak, or Peak-Hold measurements which are not triggered
>events."
>
>Sounds like other than auto-triggering, the results are the same.
>
>Dave


Like this?

Apply power, inrush current is 10A for .2 seconds.
Current drops to 1.2A for 2 seconds.
Current rises to 12.5A for 1 second.
Current drops to 1.2A until termination.

So the Inrush reading would be 10A, and the Max reading would be
12.5A. I can see some usefulness for this, since a max only meter
would falsly read 12.5A which the user might attribute to the inrush
current, instead of the event at 2 seconds.

From: Shaun on 11 Nov 2009 12:37

"notme" <notme(a)notme.org> wrote in message
news:0001HW.C71FB1C00028C68CB08A39AF(a)news.eternal-september.org...
> Fluke clamp current meters have 2 features that seem similar: peak and
> in-rush. The older models have Max (some: Peak). The recent advent in
> Fluke
> clamps is "In-rush".
>
> How do these differ? Isn't in-rush current the short, max current at
> motor-turn on? Shouldn't meters with a Max feature capture this
> accurately?
>
> Compare, for example, my old Fluke 36 (Max):
>
> <http://assets.fluke.com/manuals/36______iseng0000.pdf>
>
> and the 334 (In-Rush):
>
> <http://us.fluke.com/VirtualDemos/330shock.asp>
>
> (click "Explore" then "Selection Guide").
>
> How do Max & In-rush differ? Only in the marketing department?
> Or is there a real-world difference?
>
> Thanks,
> Dave
>

In the usual Max measurement, the input (current) is sampled and the maximum
sample is displayed, but the true maximum could have occurred between the
samples and in that case you miss the true maximum or inrush current that
your looking for. In inrush current measurements first off it's a triggered
measurement and measures for a very short period of time and it doesn't
depend on samples, I think it's an analog approach.

Shaun


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