QuantAsylum QA451 User’s Manual
Page 10
Pressing an illuminated load button again will turn the loads off. When both the 4 and 8 ohm buttons
are off, then the QA451
presents an “infinite” or open
load to the amplifier. Note that when the QA451
is open, the QA451 +/- outputs are meaningless. That is, the input signals cannot be measured when the
loads are disconnected.
Application Temperature Sensing
On the right side of the QA451 application, you can see the temperature for both the left and right
channels. Generally, under normal operation, these temperatures must remain under 60C. Above 60C or
below 5C, the QA451 will disconnect the loads and require time to cool down or warm up. The sensors
are very accurate and respond very quickly. Generally, as long as you do not impart more than 300W of
power per channel, you do not need to worry about harming the QA451. It will self-protect. The
temperature readings are provided for information only.
Application Current Sensing
The QA451 reports the current measured by the Current Sensing subsystem. The resolution is around 5
to 10 mA. That is, you will see readings jump by p/- 5 mA. On the QA451B, the resolution is
around 10 to 20 mA. For high-power amplifiers that might draw 10A or so
, this generally isn’t a problem.
Of course, if you want to measure an amp with a max current of 100 mA, then this resolution can
contribute significant errors.
DUT Power
The DUT POWER button is used to the turn on the high-side PMOS in the QA451. When enabled, the S+
and S- will be connected by a low impedance of 25 mOhms or so. This is Rds(on) of the high-side PMOS
pass device.
If the QA451 application is closed or stops responding, or if the QA451 is disconnected from the USB,
then the QA451 will automatically open the load relays and disable the load power.
Fault Conditions
If absolute current exceeds 15A for more than 2 milliseconds, the high-side switch will be disabled. A
fault will be reported on the QA451 application and the USB power must be removed and re-applied to
clear the fault and restore normal operation.
Remote Connections
The QA451 provides a simple web service that allows remote control of the settings via a REST API. If the
REST web server fails to start, you will see a message as shown below on the status bar:
