[time-nuts] FE-5680A performance

Hal Murray hmurray at megapathdsl.net
Thu Jan 5 09:44:13 UTC 2012


albertson.chris at gmail.com said:
> Question:  Can anyone measure the pulse?  How wide is it and what is the
> voltage? 

Ignacio said it was 1 us wide.

I don't have a 5680A to look at, but all the PPS pulses I have looked at are 
at least a few volts.  They are easy to see on a scope.  One common setup is 
a 5V driver with a 50 ohm series terminator.  That gives a 5V pulse without a 
terminator or a 2.5 V pulse if you terminate it with 50 ohms.

The PPS on a TBolt is 10 uSec wide.


> Have an older Tek 465 scope that is in only "fair" shape and I see nothing
> on that pin but milivolt level sine wave of about 60MHz.  I can't set the
> scope to show any hint of a PPS ...

I do have a 465.  You should be able to see a 1 uSec PPS.

Here is the recipe I would use:

Use the probe on Channel 1
Ch 1 Volts/Div: 1 V
Vert Mode: CH1

Horiz Display: A lock knobs
Time/Div: 1 uSec
Trigger Mode: Auto

That should give you a horizontal line.
Adjust the Channel 1 Position so the line is a division or two above the 
bottom.

Switch the Trigger Mode to Norm
Trigger Coupling to DC
Trigger Source to Norm (or CH1)
Trigger Slope to +
Turn the Trigger Level knob all the way to the right (CW)

Watch the TRIG light (lower right from the Time/Div knob)
It will blink each second when you get the triggering level right.

Now slowly turn the Trigger Level CCW.
When it starts triggering, you have found the top of the pulse.
If you keep going, it will stop triggering when you get to the bottom.
You want half way between top and bottom, but anything that blinks the light 
is good enough.

Now turn up the Intensity until you can see the pulse.  It might help to turn 
down the room lights.

Now that you can see something, adjust vertical and sweep to show what you 
want.

The above assumes a positive pulse.  If you have a negative pulse, you want 
the line positioned a few divisions from the top and to trigger on the 
negative slope.

If the pulse is way wider than you expect and the level is the same as you 
see on AUTO, you are probably triggering on the trailing edge of the pulse.  
Flip the Trigger Slope.






-- 
These are my opinions, not necessarily my employer's.  I hate spam.







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