Re: Oscilloscope grounding question...

How many scopes did go get with internal ground traces fused open?

** That should not happen with any scope that meets even basic electrical
safety requirements - one of which is that external metal parts ( like
the BNC sockets) must be connected to the AC supply ground terminal by
conductors of at least 1 sq. mm cross section.

Precludes the use of PCB traces alone to do the job.

Tek broke this rule with their very popular TDS210 / 220 series and had to
recall the whole lot.

My experience with this kind of fault pre-dates the TDS series by some
many years. It is part of my regular precaution, when visiting or
assuming position in an unfamiliar test site to do basic continuity
tests of this kind of internal equipment connection, digital ameter
fuses, wall power polarity, battery conditioning and source
interconnection, etc, etc, etc.

As the equipment dumped on a 'faringee' is usually dusty for some good
reason, this is just plain good sense. In practice, I've pointed out
open and dead circuits in these kinds of situations regularly, even in
equipment with fresh calibration stickers. How this calibration was
managed, I have no idea. Perhaps Yanik can illuminate inquiring minds.
Scope models exhibiting internal open circuits included, from memory,
Philips, Tek, Jiwatsu (sp?) and Nicollet.

In fact I actually own a TDS210 (since Y2K), and am listed to receive
all product and recall notices from Tektronix covering this and a
number of other models. I have no record of any recall being issued
for the unit and have not had the problem - probably because of normal
precautions previously mentioned in configuring a power electronics
test bench. I find it to be a usefull tool, once isolated in
conjunction with battery-powered laptops communicating through an
rs232 interface. I also communicate to non-isolated bench PCs through
various different isolated rs232 interfaces.

I have, however, seen similar models whose BNC sockets were wobbly
from simple brute force physical trauma. One of the problems with
light and portable equipment that should be dealt with at the design
stage.

In surviving a live wire short to ground, I wonder whether a 1mm
cross-section wire is stronger than BNC or scope shielding braid,
18AWG line cord, wall wiring or a wall breaker of random ampacity and
characteristics (not to mention all those iffy and worn socket, probe
tip and DUT screw terminals)? Why place a $2K+ piece of hardware in
the equation unneccessarily?

A mandartory ground connection is just another ignorant hand thrust
into a test circuit, when my own extranious appendages are tucked
away, where they should be.

RL

Excuse the odd posting format - original is copied from non-usenet
source, as your posting ID seems to get regularly '30-day plonked'on
my news handler. Possibly a lunar influence.
.

Relevant Pages

  • Re: PC Based Oscilliscopes
    ... prices that you posted about equipment however quoted below. ... In the last few years there is a new class of scope called real time. ... DPO's have a rapid processing cycle and also have most ... Repetitive sampling scopes are good at any type ...
    (sci.electronics.equipment)
  • Re: PC Based Oscilliscopes
    ... prices that you posted about equipment however quoted below. ... In the last few years there is a new class of scope called real time. ... DPO's have a rapid processing cycle and also have most ... Repetitive sampling scopes are good at any type ...
    (sci.electronics.basics)
  • Re: "LVD" versus "GPSD" when supply voltage is 24V (SELV from fixed installation)
    ... voltage is below 50V (and therefore outside the scope of the LVD)? ... However as your equipment is electrical the EMC directive will almost certainly apply, even if it's obvious that no testing is required. ... See the various books by Tim Williams for good practical advice on EMC compliance. ...
    (sci.engr.electrical.compliance)
  • Re: VFD induces terrible vibration in 2 different motors. SOS
    ... the best analog scope ever made: ... rusty Degree in Electronics. ... But sure as hell:) I wuz not going to stick probes into equipment I ... I damaged my one HP KB Electronics VFD a couple years ago. ...
    (rec.crafts.metalworking)
  • Re: First oscilloscope
    ... I do pic programming, Ir circuits, analogue circuits and use 433MHz AM ... I want to get an oscilloscope to analyse the circuits I build and, ... You can get you a vellman PC500 scope for about 300 bucks wich is suppose to ...
    (sci.electronics.basics)