According to Eric R Snow :
On Mon, 3 Oct 2005 14:22:21 -0400, Ned Simmons
wrote:

In article ,
says...
SNIP


If you've got an o'scope you can look directly at the
encoder channels to eliminate any possibility that it's the
readout, if that's what you mean by display error. Less
convenient, but workable, would be a voltmeter or two. Or
even an LED on each channel, as long as you're careful to
limit the current based on the encoder's drive capability.

Ned Simmons
Ned, I have a scope. I don't really know how to use it. I need to get
a book on oscilloscopes in general. The scope is a Tektronix 465B.

A nice 'scope.

The
only probe I have is one with a red and black wire terminating in
little hook shaped clamps. If this will work can you tell me how?

[ ... ]

if it is.) Connect the ground clip to the readout chassis or signal
ground.

The main question is whether he can identify the ground clip on
the probe as described. Most Tektronix scope probes of relatively
recent vintage have a groove about half-way back from the tip to the
entrance point of the cable. A clip, sort of like a small version of a
hairpin clips into this to connect the ground clip to the scope probe's
ground.

Older Tektronix scope probes, as well as ones by Hewlett
Packard, had a threaded hole in the side of the probe, into which the
end of the ground clip screwed.

Recent Tektronix scope probes have a coaxial tip, with a sleeve
surrounding a tiny point. An extension slips onto this for most work,
with a spring-loaded hook which is exposed by pulling back on a skirt on
the probe tip.

For really high frequency work, an alternative tip slips on,
which picks up ground from the sleeve, and has a very short projection
for the center conductor.

Your color scheme does not sound like any Tektronix scope probe
which I have seen.

Note that any probe needs to be tuned to the scope. This is
done by connecting the probe tip to the calibrator output (a square-wave
pulse), and adjusting one (or more for higher frequency probes)
adjustments to maximize the squareness of the displayed trace at the
corners. Adjusted too far in one direction, and the trace will curve
gently from the vertical to the horizontal. Adjusted too far the other
direction and the trace will overshoot beyond the horizontal, and then
return to it -- sometimes with one or two ringing overshoots in both
directions.

If there is more than one adjustment for the probe (usually in
body of the connector to the scope, but rarely on the scope probe
itself), one adjustment will adjust the squareness of the corner, and
the next will adjust a portion of the horizontal top or bottom of the
square-wave train. I've seen some (high voltage probes, with 10KV
maximum voltage) with four or five adjustments in a large box at the
connector end.

Some of the older Tektronix (and others) probes will have a
knurled knob where the flange of the probe joins the body. Loosen this,
and unscrew or screw tighter the tip end to adjust the response of the
probe.

Once your probe is tuned to the scope, you should not need to
re-adjust it until you move it to another scope (Or for a scope with
plug-ins, until you move it to another plug-in).

You probably don't really need to tune it for what you are
doing, but if you don't, you may see the pulse height change with speed
of motion (as the pulse never really reaches the top of the waveform).

All you need for encoder channel B is to make a connection to the center
pin of the scope's CH2 BNC connector. If you don't have a mating
connector, you can stick a pin in the center of the connector and use a
jumper, just be careful not to damage that nice old scope.

Indeed so.

Set the toggle under the VOLTS/DIV knob to GND on both channels.

Push in both CH1 & CH2 pushbuttons on the left of the screen, all the
rest in that group should remain out.

Set the TRIG MODE to AUTO.

Set the TIME/DIV KNOB to around 1ms. Make sure the coaxial knobs are
locked together.

Now fiddle with the POSITION controls way over on the left to get the
two traces separated on the screen. If you don't get the traces, try
fussing with the SOURCE and LEVEL on the lower right. (I'm winging this
by looking at a picture of a 465B that Google found for me.)

Set the toggle under the VOLTS/DIV knob to DC on both channels.

Set the VOLTS/DIV knob to 2V on both channels. If the probe is a 10:1,
set that channel to .2V

Turn the readout power on. You should the encoder transitions when you
turn the shaft. Play with the trigger settings if you want to synch the
sweep to the signal with continuous rotation.

That should get you started. Don't be afraid to play with the knobs, you
can't hurt anything. Hopefully someone else will chime in if I've missed
anything obvious.

Excellent scope operation at a distance course.

Enjoy,
DoN.
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