QuantAsylum QA401 User manual
QA401 Quick Start
Connecting the Hardware
1. Plug in the QA401 hardware with a USB
cable (not supplied). The OS should
recognize the hardware, finish installing
and then you should see the
application configure and connect.
2. Once connected, you’ll see an
indication in the lower left corner of the
application.
Starting Acquisition
1. Go to the File menu and select Reset Startup
Defaults. This a quick way to put the hardware
and software in a known state anytime.
2. Scroll the control panel so that you can see
the Run/Stop button. The panel can be
scrolled by clicking and dragging in an empty
area of the panel itself OR by moving your
mouse into the control area and using the
mouse wheel.
3. Press the Run/Stop button. When it is
illuminated, you are running. You should see
yellow spectrum data appear and update.
4. There are two ranges on the QA401:
+6 dBV and +26 dBV. When the +26 dBV
range is selected, the attenuator is enabled
and you will here a relay “click” as you switch
between the two. The +6 dBV range is more
sensitive for measuring noise.
5. Select the +6 dBV range.
Shorting the inputs
1. To measure the noise floor of the device,
you need to short the inputs with a low
impedance shorting block (not included).
These are often called “BNC shorting
blocks” or “terminators”. You can find these
for sale on Amazon or your favorite
component supplier. Search on “bnc 75
ohm terminator”. The precise impedance
isn’t important, it just needs to be less
than a few hundred ohms.
2. If you do not short the inputs, then you’ll
measure the noise of the internal input
resistors—and the noise contribution from
the inputs 100K resistors can be quite high.
3. You can short just the left or just the right
inputs, or both.
4. Never short the outputs, it can degrade
the output opamp performance.
Making a noise
measurement
With the QA401 running, the inputs shorted
and the +6 dBV input range selected, you
should see a spectrum similar to that shown
in the picture. Note the absence of spurs.
You can also read the noise is -115.3 dBV.
Your unit should measure within a dB of
this. This is the noise measured within a 20
to 20 kHz bandwidth, and it works out to
roughly 1.8uVrms.
Loopback Connection
Leave the L- shorting block applied and
using a BNC cable (not included) connect
the left + output to the Left + input
Loopback THD
Measurement
Press the Gen1 button. This enables the
internal oscillator.
You can change the amplitude or frequency of
the oscillator by clicking and holding (long
press) on the Gen1 button OR by holding the
CTRL key and clicking on the button. Any
button with a dot in the upper left has a menu
that can be activated this way.
Verify your THD measurement is around
-109 dB.
You can click on the peaks to add markers.
Pressing “D” will remove those markers.
Other Controls
You can change the depth of the FFT using
the “Roller” buttons. This control can be
changed by clicking on the up/down arrow,
or by hovering over the arrows and rolling
your mouse wheel.
Need more help?
Forum: http://Forum.QuantAsylum.com
Contact: Suppor[email protected]
The PDF manual is available from the application
Select “Help -> Launch Help”
Or, check in the installation directory
C:\Program Files (x86)\QuantAsylum\QA401\Documentation
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