Re: [CAD_CAM_EDM_DRO] Re: oscilloscope for CNC

Hi Tanya;

A few comments.

By digital I mean digital storage scope, which is not to be confused
with an analog storage scope. These are differrent beasts.

Some of the preferrable features may only be found in higher end
scopes. But I do consider voltage and frequency readouts and on
screen cursors very important, which can be found on older scopes.

A scope with isolated inputs would not be grounded. In fact if you
have a non-isolated scope you have to be extremely careful when using
such a scope on industrial circuits. If the scope does not have
isolated inputs it may be advisable to get an isolation amplifier.

I believe that the minimal input bandwidth that you will want in a scope
is 100MHz. Such scopes are not hard to find, but you can get by with a
lot less, if you can work with the limitations. If your looking at
digital scopes understand that the sampling rate and analog bandwidth
are two seperate things. Also advertised sampling rates are (how
should I say this) often hard to interpet.

Some of the scopes you have listed are rather old even for the used
market. The only experience I've had with scopes have been Tektronix
models, so that leaves me heavely biased. Tek does have a TDS series
that seems to be missing from your list.

Buying used is up to you. Do realize though that scopes like all
hardware age, calibration or repair of old scopes can be excessive. If
this is your first scope and you have limited background in electronics
I'd would suggest looking for the absolutely cheapest scope you can find
to develope a bit of experience on, and to toss out if damaged. On
the other hand if your reasonably confident in your abilities I'd opt
for either new or a realitively recent used scope.

No scope is one size fits all. What you want is a general purpose
scope, the more functions it has that are usefull for industrial systems
the better. Do be aware that there are a huge number of scopes that
are not suitable at all for this sort of work.

You didn't mention where you are at, but yes used scopes are available
all over the US. You can even find web retailers of used equipment.
If you happen to be so lucky to be in the silicon valley there are
stores all over theat area that handle used equipment. Generally most
large cities in the US have at least one business dedicated to moving
surplus electronics. Another option is DoveBid, which does online
auctions of bankrupt busineses and sell offs. DoveBid is nice in
that a lot of companies that have failed recently are very new, thus the
hardware is very new.

thanks
Dave


tanyasapa wrote:

>Thanks to Jack, Harvey, Jens, Alex, Vic, John, Vince, Charles, Dave,
>David, Lee, Stephan, Bernard, Jon, Joe, William, Jack, etc.
>
>Summary:
>
>PREFERABLE FEATURES:
>dual channel
>triggered sweep
>onscreen readout
>Minimum 50mHz bandwidth
>
>
>>=100mHz.
>>
>>
>2x frequency to be measured
>Digital
>period measurements
>counting
>frequency readout
>voltage measurements
>maths function
>printing
>input isolated and grounded
>wide voltage range
>storage
>accurate timebase
>scroll mode
>color
>
>
>BRAND:
>Tektronicx - good
>HP - good, odd logic
>Kenwood - good
>Telequipment - avoid
>Fluke - portable, rugged
>
>MODEL:
>Tek 545 (vacuum, lots of capability)
>Tektronix 2000+ portable
>Tektronix 7000+ mainframe, plugins,
>Tektronix 5000+ less money
>Tektronix 500+ stay clear, vacuum tube, space heater
>Velleman: single channel, handheld, 10mHz, digital,
>Fluke 92B Scopemeter - big bucks, manual with examples
>
>POOR MAN'S:
>http://www.stud.fh-hannover.de/~heineman/freeware.htm
>http://racket.bitscope.net/
>
>RECCOMENDATION:
>buy used (if you happened to be in USA/Canada :-(
>
>Is there a 1 size fit them all?
>
>
>Addresses:
>FAQ: http://www.ktmarketing.com/faq.html
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