New Quantasylum QA190 Differential Input Probe

[stellavox]

QA190 Differential Probe

Battery Powered and works quite nicely. $79. You (currently) get one FREE when you order a 400 (or 100 oscilloscope)

Charles

 

[31697B]

Thx for QA190 info... I am getting one asap.

-Richard

 

[hochopeper]

Only available in the USA and it's only shipping that's free not the whole QA190 when you get the QA400 or QA100. Looks interesting though it's a shame about the 150V RMS limit which precludes the mains analysis in some countries (if they ever chose to sell to us).

This is an interesting quote from the QA190 product page:

There is a reason for doing this in a CAT III rated differential probe with a 1000V rating. That reason is safety. You want to attenuate the signal early and then deal with a small voltage. But the downside of that is that is that you are gaining up the noise, which isn’t good for audio. Since the QA190 isn’t designed for 1000V like the other diff probes (remember, QA190 max is +/-150Vrms), we opted to take the lower operating voltage and much better noise performance.

We also opted for a 2Mohm input impedance on the QA190. Most differential probes rated for very high voltages have a 10Mohm input impedance. And if you are measuring 1000V at the panel that makes sense. But again, the QA190 isn’t designed for operation at the panel. Thus, we reduced the input impedance to help with noise.

Outside of those two departures, the internals of the QA190 are Jung’s classic “Buffered Input Balanced Line Receiver” from Chapter 6, figure 6-30, of the Analog Devices Op-amp Application Handbook. With some updated opamps, of course.

 

[31697B]

The CMR holds up fairly well to 100KHz esp on X100 range... its about 10dB better than X10 range. But both are still good. A CMR trim inside did not pick up any further improvement when I tried to adjust it. So, it is good as it will get from factory. The combo of volt and amps can help measure Power of amps, to.... up to 150v.... with real loads applied (speaker). Usually, hard to do with balanced power amp outputs.

I have a hand-held FLUKE 43A (ac power analyzer) that does some things similar in measuring Volts/Amp but cost a LOT more. It has built in FFT but with this Diff probe used with QA400 you can get the data a much lower cost and over a wider frequency range.


THx-RNMarsh