wrote in message
ups.com...
On Sep 4, 1:30 am, Chuck Harris
wrote:

HP410LR? That's a new one to me. I am aware of the
410A, 410B, and 410C,
but not the LR. The 410(A,B,C) have their DC/Ohms probes
wired directly to
the instrument, and their AC probe has a vacuum tube
diode in it, and plugs
in by way of a Stereo Phone Plug.

Can you describe this instrument for us?

-Chuck

Sorry, it's a HP 400LR, a rack mount version of the 400L.

My unit has binding posts.


The 400 series meters are AC meters, they do not have
DC or resistance ranges. The 400L is the same meter as the
400D and H other than the special meter movment which
displays the voltage on a logrithmic scale and has a linear
decibel scale uppermost. It does not need any special probes
or accessories. The meter movment is a 1% tracking meter
movement with a mirror scale to eliminate parallax similar
to that used on the 400H. BTW, the only difference between
the 400D and 400H is the meter movement and use of a mirror
scale on the meter. Meters made after -hp- introduced
taught-band meters all have the same tracking accuracy since
each meter was individually calibrated by machine. The only
difference here is the use of a mirror scale on the 400H,
the 400D will also track to 1%.
There were at least three versions of the circuit used
in 400D and H meters so you must get a handbook for the
serial number series you have. The later meters used a
circuit which is substantially different than the early
meters.


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Richard Knoppow
Los Angeles, CA, USA