[Amps] grid resonance

[Tom W8JI]

>I read the PDF about the HP 4191A from Coilcraft and didn't 
>see anything
> out of the ordinary excapt some LCR meters bound to not to 
> be calibrated.
> Either this or they were used to measure an inductor 
> outside of their range.
> In any manual that comes with any decent LCR meter, they 
> tell you that
> the measurements are frequency dependant, and that the 
> frequency has
> to be changed according to what range your in. If the 
> meter measures a
> false reading after this, it is out of calibration. If the 
> meter has a range that
> says it will measure a certain device, then it should as 
> it has to be calibrated
> to measure on at that frequency. If I recall, the 
> Tektronix one was an older
> style LCR meter with a low frequency range. The Meguro's, 
> I'm not familiar
> with as to how they work (two wire or four wire, etc). 
> It's funny they didn't
> compare the 4191A to a General Radio (GenRad) or a ESI 
> (Tegam) which
> makes measuring L, C, and R their specialty. All this 
> whole text showed
> was that the 4191A had a 100 MHz measurement function 
> available, nothing
> more. It also showed that if the Tek, Meguro, Boonton, and 
> the other HP said
> they would measure the device, they was either out of 
> calibration or someone
> was trying read a device outside their range in my 
> opinion. I'll guarantee you
> that if HP said the 4192A would measure a certain device, 
> it would before it left
> the factory as they are one of the few direct NIST 
> traceable labs available. I'll also
> guarantee that a precise NIST traceable standard was used 
> to calibrate it at
> HP too. After it left, it's untelling who may have had 
> their fingers in it. If it
> measured a device correctly there, it should at another 
> location.

You need to reread the article Wil. What they said and what 
you got from it are two totally different things. You also 
better look at how the equipment works before launching into 
oversimplifications about how things are all the same.

Impedance test sets like the 4191A go through a 
self-calibration to normalize out interconnecting cable 
lengths all the way up to the upper frequency limit. This 
makes it possible to obtain precise impedance readings even 
on 1GHz though test cables and fixtures. It reads Q D X L C 
R Y and a dozen other parameters directly at any frequency 
between 1MHz and 1000MHz. Unless an instrument has a 
self-calibration mode to normalize out lead or fixture 
induced errors it will never read RF impedance precisely.

On the other hand maybe this is just a definition problem of 
what "good" and "accurate" mean. You seem to think cheap CB 
power meters and CB amplifiers are top notch, so it may be a 
problem related to what words like "good" or "accurate" 
actually mean.

73 Tom