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

[Dave]

Just used my HP-428B yesterday to monitor the current in a 1200V line to 
a PMT with an internal divider. Is really nice that I don't have to 
worry about making high voltage electrical connections to check current. 
  Always wondered if I had one of the few left that had a working probe 
on it.  Guess there are some others out there.

Dave


Michael Baker wrote:
> 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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