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

[paul swed]

Like my 428 also. But I have a tube version hybrid. It is drifting a bit and
one day I will get off my butt and address that. But its not bad enough to
open the case actually.
Using the ad588 as a current source is a good idea but semi expensive.
I looked up the ad558 yesterday and digikey wants $38 each.

On Wed, Jan 13, 2010 at 11:26 AM, Michael Baker <mpb45 at clanbaker.org> 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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