[time-nuts] [OT] Re: HP-428B What I really meant....

Pete Lancashire pete at petelancashire.com
Wed Jan 13 16:52:57 UTC 2010


Tek current probes were a little less sensitive to heat but
just a warning to who may get a HP or Tek current probe the
ferrite is VERY VERY VERY fragile. Not only from shock but
watch out when you close the probe it chips easily

oh .. not sure about the HP but the cables on like the Tek
P6045 the cable to the probe has a lot of little wires in it
and does not like tight bends.

-pete


 > Hello, TimeNutters--
>
> Oops!!  I goofed--
>
> I meant to say HP/Agilent 428B Sensitive Clip-On DC Milliammeter.
>
> Only the latest revision model with a serial number
> prefix of 995-xxxxx is worth having.
>
> In their last revision, HP retained a couple of tubes in functions
> where they felt early 80's transistors would be less reliable.
> However, most of the circuitry is solid state and is all on a
> very nice printed circuit board.  The unit went out of production
> in 1984.  The probes are extremely fragile and if dropped
> or exposed to excessive heat for long periods of time
> the ferrite cores or the Mu metal shields will be degraded.
>
> The manual warns against storing the probe on top of
> any hot instrument top.  My 428B has been an invaluable
> and frequently used test instrument on my work bench.
> Alignment was a little tricky but once done, my unit
> has been in use for over 10 years with no problems.
> It is very handy for measuring low current drains of
> circuits down around the 1 to 10 milliamp range. Actually,
> on the lowest scale (0 to 1mA) you can accurately measure
> currents down to 0.1mA.
>
> Mike Baker
> ----------------------------
>
>
>
>
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