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Old 18th September 2006, 07:51 AM   #1
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Default HPHV regulator measurement

On the HPHV regulator manuel

www.euronet.nl/~aespreng/Shuntregv11d/Manual.pdf

There are 2 graphs.

1. Gain Vs Frequency
2. Phase Vs Frequency

Does anyone know how the second curve can be measured?
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Old 18th September 2006, 01:17 PM   #2
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Google "small signal loop stability measurement" or some such -- you insert a 50 ohm resistor into the control loop and, with a 50 ohm transformer to isolate your spectrum analyzer from the power supply), measure the gain and phase with a spectrum analyzer or phase-gain meter.

you can do all of this in DSP -- or with a digital scope -- the transformer needs sufficient bandwidth however -- probably from a few hundred Hertz to several hundred thousand. I know that Softwire has an FFT function which renders both magnitude and phase -- should be the same in LabView.

ok, i'm going to guess that you don't have a $10,000 spec analyzer -- you can measure the gain with a sweep generator and an ordinary scope --

If you want to measure phase in "analog" here's the technique used by Hewlett Packard in their 3567 phase-gain meter -- (and intersil wrote an interesting application note on their site which will measure phase acurately to 10 MHz ( http://www.intersil.com/data/an/an9637.pdf ), Audio Amateur had a similar article sometime in the early 1980's -- take a pair of high speed comparators and measure the difference in zero-crossing time by summing the voltage -- the integrated value will give you a voltage proportionate to phase.

The devices in the Intersil article are pretty hard to get -- but I have used the technique with both the HFA3102 in SOIC and with through-hole NPN transistors -- used Texas Instruments selectable-output current feedback opamps.
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Old 18th September 2006, 05:22 PM   #3
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... or use an AD8302 network-analyzer-on-a-chip.....!

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Old 18th September 2006, 06:44 PM   #4
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Quote:
Originally posted by janneman
... or use an AD8302 network-analyzer-on-a-chip.....!

Jan Didden
Not bad for a $24 chip --

btw, you can sometimes purchase an HP3575 for less than $50 on EBay -- then you don't have to do any soldering. (There's one running for about $10 as we speak.)
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