[Test-Equipment] HP equip questions

[Stan]

Gary Chatters wrote:
> 
> >
> >It seems odd that there would be an L version preceeding a B version, but
> >it sounds like the B is the later model.  It just opposes HP's normal A/B/C
> >version scheme -- the only other L variant I know of is the 5245L counter,
> >which was also available in a (presumed-later-model) M version.
> >
> 
> I have never seen any official explanation of how HP used
> suffix letters.
> 
> In many cases they used A, B, C, etc for newer versions of
> the same instrument.  Sometimes the step was rather large as
> when the 410 multimeter went from the 410B, which was the
> large old style vacuum tube version to the compact 410C
> which still used a vacuum tube.  Later 410's went to solid state,
> but were still referred to as 410C.
> 
> Suffix letters were also used for variations in features.
> The HP400 AC voltmeter had the 400E, 400F, and 400G versions.
> That might be the order they were introduced, but the suffix
> signified different features and they were all in the catalog
> at the same time.  These meters also had L suffix versions,
> 400EL, 400FL, and 400GL where the L referred to logrithmic meter scale.
> 
> The 5245M may have come out later than the 5245L, but it also
> has different specs (high stability time base) and was in the
> catalogs at the same time.
> 
> In an earlier message I noted that the 5245L could have the
> 10544 high stability time base.  I think this is as good as the 5245M,
> but I don't know anyway to tell that you have it except to open the
> cover and look.  Anyone know about this variation?
> 
> Gary
> 
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My $0.02:

In my limited experience, although HP/Agilent most often used the usual
A-B-C sequence of suffices to indicate progression of design and/or
differing sets of features, occasionally there were reasons for
non-obvious lettering. For example, the HP 5245 counters had both an "L"
and an "M" suffix. The *only* difference between the two was the
stability of the timebase, where "L" was the (relatively) low stability
version and "M" was the medium stability version. I am not aware of a
high stability version, but this was just about the time that the HP
10544A/B (and then the 10811A/B and 10811D/E) 10 MHz timebase models
were introduced, and shortly thereafter the 5245 line was made obsolete
by the 5345A that incorporated the 10544A (and later, the 10811A)
module.

BTW, the aging rates of the 5245M timebase and the 10544A module are the
same: 5x10E-11 per day, but the short term (1 sec) stability for the
10544A is about five times better than the 5245M: 1x10E-11 as opposed to
5x10E-11. Does this mean that an HP 5245 with a retrofitted 10544A
timebase should be called an HP 5245H? (or would that be an HP 5245N?)
;-)

A more recent example is the Agilent ESA series of spectrum analyzers.
"ESA" (supposedly) is an abbreviation for Economy Spectrum Analyzer. The
ESA-L models are their "Low cost" series, and the ESA-E models are their
"Expandable" series that incorporate expansion slots on the motherboard
for add-on option cards. Likewise, the predecessors of the ESA
analyzers, the 8590 series of spectrum analyzers, had similarly
configured "L" and "E" versions.

Stan