Date: Tue Oct 14 16:39:45 2008

Author: Bill Norwood

Subject: Re: in need of some good multimeters

Post:

Hi Paul,

Many thanks for the picture about fuse access and the remarks about this BK
Precision Model 5360 multimeter with easily-accessible fuses, and with a
built-in safety whereby it would be impossible for someone to attempt to
replace a fuse while a test item were still connected to the meter.

Does anyone have any student lab experience with it? Is it a good one?

I note that it is a discontinued BK Precision item, and that the
mfr-specified replacement is a model 2890A, whose specs depict so many
functions that I wonder whether our students might become bewildered. Did
they escalate substantially between these models? Does their new model
retain this easy fuse replacement feature?

I know these are questions I should be asking the distributor/manufacturer,
but I just wanted to give you all a shot at them also.

Many thanks, all, for any information and for your great patience thus far
with me in dealing with what I perceive to be a problem.

Bill Norwood
U of MD at College Park





-----Original Message-----
From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
Behalf Of Paul Nord
Sent: Tuesday, October 14, 2008 11:09 AM
To: tap-l@lists.ncsu.edu
Cc: Paul Nord
Subject: Re: [tap-l] in need of some good multimeters

I've got one nice BK Precision meter on which the fuses are easily
accessible via a snap-off cover plate. The plate is on the front of
the meter and has holes which surround the banana plug sockets. So
this pretty much guaranties that the leads are disconnected when you
change a fuse. It's a simple design which seems to overcome these
concerns.

And to encourage you to put that cover back on, all of the markings
for the dial settings are on the cover.
http://physics.valpo.edu/staff/pnord/temp/bk5360.jpg
Sorry about the reverse video on the image... stupid web cam default
setting that I'm not going to bother to fix.

Paul


From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu]
On Behalf Of Dan Bernoulli
> Sent: Monday, October 13, 2008 1:14 AM
> To: tap-l@lists.ncsu.edu
> Subject: Re: [tap-l] in need of some good multimeters
>
> Bill, etal,
>
> I have read with interest your frustrations with fuses in
> multimeters. Unfortunately the fuse problem is really a cost versus
> safety issue. The manufacturer can't control how the meter will be
> used and even though all kinds of warnings are put on the meter
> someone will inevitably use the meter in a situation that is unsafe.
> By putting the fuse inside, if the meter is put across an overload,
> the vaporization occurs inside the meter housing where it can
> (hopefully) be contained. Typically the housing is designed so one
> has to dissassemble the meter inorder to replace the fuse. This is
> normally done in such a way that one must disconnect the leads to
> the meter to take it apart. This is a simple but effective way to
> prevent stupid things from happening. Having spent six years in the
> Navy as an electronic tech I can vouch for the wisdom of such
> construction.
>
> Envision someone working on a high power transmitter on a ship.
> Perhaps several thousand volts and some kw of power. At best the
> fuse blows before the meter vaporizes. In spite of what Myth Busters
> might say, it has happened. Now if the fuse does blow and the
> "technician" decides to replace the fuse, if it was external,
> removing the fuse might not be an issue, but putting it back in
> could be really exciting as the arcing and sparking would likely
> vaporize the fuse, fuse holder and person holding them as they make
> contact with the live circuit.
>
> That said, in recent years much progress has been made in making
> fuse holders safer. For example, code now requires no physical
> contact with the live circuit when a fuse is replaced. It has been a
> while since I did any nec stuff but I suspect there are now
> restrictions on the type of fuse that can be used in measuring
> devices. Although we all wish for more easily changed fuses, or
> better automatic reset devices for all but catastrophic overloads, I
> sincerely doubt whether the manufacturers are going to bother. As
> someone pointed out we all want low burden (i.e. low resistance
> meters) so they don't load the circuits we measure. A tenth of an
> ohm is perhaps common. If we connect across a 110 V circuit that
> gives us an instantaneous few kw of power the meter has to contain.
> It can be done but it is expensive and probably wouldn't fit in your
> pocket.
>
> Although I wish otherwise I suspect your grumblings may fall on less
> than sympathic ears.
>
> Dan Beeker
> Indiana University
> From: bnorwood@umd.edu
> To: tap-l@lists.ncsu.edu
> CC: teg@physics.umd.edu; amonroe@physics.umd.edu;
> edusales@mouser.com; cservice@omega.com;sales@electronickits.com;
fluke-info@fluke.com
> ; egram@metrictest.messages2.com; Ben_Pearson@vwr.com;jtemple@axisusa.com
> ; cindy.paul@grainger.com;
nvia@arcade-electronics.com;Debra.Anderson@mouser.com
> ; bhenson@newarkinone.com;
HeckendM@mscdirect.com;renee.lewis@alliedelec.com
> Subject: Re: [tap-l] in need of some good multimeters
> Date: Mon, 6 Oct 2008 11:24:00 -0400
> Hi Taplers,
>
> Here I go again, We have the old Keithley 168's, and, now the new BK
> Precision 2831D, both which invite a "labor of hatred and anger" as
> they require that the meter be partly disassembled in order to
> replace the current fuse(s) - and the students blow a lot of them.
>
> I do not want the "opportunity" to build external meter-protecting
> fuse boards, instead I believe that meter-makers should get the
> message about what we need. Surely with thousands of schools across
> the country using digital multimeters it should be practical for
> some meter maker to manufacturer what we need.
>
> As you will see I am cc'ing makers and distributors of meters whom I
> know about - but that is not many. My request is that we "impact" as
> many meter makers and manufacturers as possible with this
> information, once and for all, so that within a few years we will be
> able to buy meters more usable in student labs. Could you please
> forward this e-mail to any meter makers and meter distributors you
> know about.
>
> Many thanks for any efforts,
>
> Bill Norwood
> U of MD at College Park
>
>
> From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu]
> On Behalf Of Sharah Yasharahla
> Sent: Monday, September 29, 2008 10:33 AM
> To: tap-l@lists.ncsu.edu
> Subject: Re: [tap-l] in need of some good multimeters
>
>
> We have 3 different kinds; Triplett 9005-A, 9300GB and SE MM6287 ,
> there has been some trouble in measuring the current in circuits
> Sharah Yasharahla
> Lab Coordinator
> Physics Department
> Science Center Rm. 192
> 404-270-5847
> Each passing day expands the frontiers of man's knowledge , bringing
> to light more and more of the Divine wisdom in creation
>
> See how Windows connects the people, information, and fun that are
> part of your life. See Now





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