[AMPS] Re: Circuit for measuring RF voltage...

[Jerry Devine]

On Thu, 23 Nov 2000 16:06:42 -0000 Peter Chadwick
<Peter_Chadwick@mitel.com> writes:
>>
>>Rich said:
>>I use a BNC "T" with stiff wires soldered to the pins on one side.  
>>This allows me to clip on a 100 to one oscilloscope probe,  allowing me
to
>>measure V across 50-ohms.


>I haven't seen an analogue 'scope guaranteed to an accuracy of better 
>than +/-5% of full screen.  That means a possible power error of around
+/-10%, 
>excluding probe errors. 

This is interesting, my Tektronix 2246 has a vertical deflection rating
of WITHIN +- 2% 15deg C thru 35deg C!

And it's SmartCursors (tm) Voltmeter has +- .5% of reading of reading +
2%
of one vertical division + 250 microvolt under DC voltage measurement,
In AC measurement 25hz thru 25mhz it's +- 2% of reading +15% of one
vertical
division + 1 millivolt.  Above 25mhz to greater than 100mhz it's +
.5db/-3db
+- 1 milivolt and follows the trigger system's frequency response curve
which
is excellently rated for a scope of it's class.

Now I think these numbers mean you have now seen one scope that does.

>Digital ones can get to 1%, although you have to watch 
>analogue bandwidth ratings, and aliasing problems if you're not running
single 
>tone. Add the probe error too. 

Good poynts |-).

>Any of these methods requires calibration against a known power source
at the >frequency of operation. 73 Peter G3RZP

This isn't an issue with real measurement men! We always test/meausre
standards
before any critical measurements. And all measuring equipment is past
their
warmup period.

73,    Jerry                                     krr2ak@juno.com
[text|uuencode|59kb ea]                                                  
        'Y2K ?   Because 1k is 3 decibels down in amplitude. 9991 krr2ak'


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