> Is this probe OK? I don't know what kind of connector the 465M has.
>
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3109813829&category=1504


The Tektronix 465 series uses a BNC connector (female jack).
Any probe using a mating BNC connector (male plug) will
electrically couple to the scope circuitry and work fine.

On my Philips oscilloscope, I set the vertical deflection amp
knob to to 0.1V/div.  With 0.3 volts at the scope panel's jack,
I get 3 divisions on the screen.  With an X1 probe, 0.3 volts
at the probe tip gives me (about) 0.3 volts at the jack.  But
the low input impedence (1M ohm) and cable capacitance limits
the displayed frequency response.

With an X10 probe installed, 0.3 volts at the probe tip gives
me 0.03 volts at the front panel jack.  So I have to mentally
adjust when setting the vertical deflection amp's gain setting.
If I want to see 0.1 V/div on the screen, I have to set the knob
to 0.01 V/div setting.  The X10 probe's higher input impedence
(10M ohm) and better capaciance figure improve the displayed
frequency response.

The X1 probe give you better sensitivity.  The X10 probe gives
you beter frequency response.

As I recall, 465-specific probes have an additional pin on the
outer rim of the probe's BNC plug.  This pin makes contact with
a ring on the scope's BNC jack.  This "tells" the scope whether
the probe is operating in X1 or X10 mode.

When a X1 probe is installed, a lamp illuminates under the
vertical deflection amp's actual V/div setting.  When a X10
probe installed, a different lamp is illumiated so that the
effective V/div setting is shown on the vertical deflection
amp's knob.  So the scope automatically adjusts for X1 vs X10
and you just read the vertical deflection off the front panel.

With a non-Tek specific probe installed on a Tek 465, you just
have to do the vertical deflection arithmetic in your head.


Most probes have a compensation adjustment to match the probe
to the oscilloscope's input.  It's usually a small screw in a
rectangular block near the probe's BNC plug.  To set it...

Attach the probe's BNC plug to the scope's input.  Hook the
probe tip to a 1KHz to 10KHz known-good square wave.  (Some
scopes have a square wave output on them just for this purpose.)
Adjust the probe's compensation screw until the corners of the
displayed waveform are as "square" as possible.  (I suggest you
play with the adjustment to see the distortion introduced by an
impedence mismatch.)

After adjusting the probe on 1 channel, check the probe on all
other input channels so you know how much distortion that probe
introduces on each of your scope's input channels.

                                                Lee Jones

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