Hi, I’m Brian Boswell, an R&D Engineer with Keysight Technologies.
I’ll be demonstrating the PA2201A IntegraVision Power Analyzer today for measuring high crest
factor signals.
High crest factor signals are very common today in high efficiency signal generation,
such as switching power supplies.
Initially here, I’ll be demonstrating the measurement capability by simulating voltage
and current waveforms with a dual-channel 33522 Signal Generator, outputting the voltage
waveform as a simple sine wave and simulating the current waveform as a high crest factor
signal with an arbitrary waveform.
Run those into Channel 1 and you can see we have a normal sinusoid for the voltage channel
and a very high crest factor for the current waveform.
If you remember, crest factor is defined as the ratio of the peak to RMS value of the
signal.
The PA2201A can actually measure crest factors of up to 3 on a full-scale signal.
This, coupled with the 16-bit A to D allows very high fidelity signals to be measured
without up-ranging of the channel.
So as you can see on this particular setup, that I am actually measuring my waveform on
my 2-amp range and I have a full-scale 2-amp signal with a crest factor of 2.985 – right
at the crest factor of 3.
You can see that on the waveform as the signal just crest at six amps peak.
I will now change the setup and I’ll show how we do this with an actual circuit that
we’re measuring.
I’ve reconfigured the system to be actually measuring a real circuit to demonstrate the
high crest factor measurement capability of the PA2201.
The circuit that I’ll be measuring is show here in this diagram.
I’ll be actually measuring with an input signal of just wall power with a switched
output.
We have the input characteristics measured on Channel 1, both the voltage and the current.
The output characteristics of this circuit we’ll be measuring with Channel 2 and the
actual circuit is nothing more than a full-wave ridge rectifier with a 160-ohm resistor and
a 40-microfarad capacitor load.
A little analysis of this circuit will show that’s not a very good bridge rectifier.
I’ve intentionally not put enough capacitance on the output, such that we’ll have a lot
of ripple and be able to demonstrate the high crest factor current waveform on this.
So I’ll now turn on the power.
The PA2201 started trigger and it now auto-ranged and you can see the signals that we’re going
to be measuring.
On the top set of waveforms are the voltage waveforms, with the yellow being the voltage
waveforms.
Notice you’ll see the full AC signal on the input and the rectified signal as the
output signal.
The middle set of traces are the current waveforms.
Notice that the input current waveform is bipolar and the output is unipolar with the
rectification that’s going on.
And finally then we have the power and you might say there’s only one signal for the
power but there’s actually two.
The power is identical for the input and the output and let me demonstrate that by just
adjusting the offset a little bit.
Sure enough you’ll see the input and output power are identical, as we don’t have any
loss in the system.
We’ll now take a look at the signals, show the crest factor.
I’m measuring the output characteristics, so I have 130 volts AC with a 127 volts DC.
So indeed, we’ve got a lot of rectification going on.
I’ve got 1.27 amps RMS being dissipated in the 160-ohm load and if you notice I have
about 87 volts worth of ripple on this output.
So indeed, not a very good full-wave bridge rectifier at all.
If you come down to the current, you can see I have about a 2.6 crest factor on that current.
We’ll now flip over and look at the efficiency of my bridge wave rectifier.
That pulls up my push button efficiency panel and you can see that I have 107 watts of input
power and the output is 100 watts, for a total efficiency of 93.66 percent.
I hope you found this presentation interesting and informative on the measure of high crest
factor signals using the PA2201A.
Thank you.