Week11 : Group assignment
Observing signal
Multi-function oscilloscope.
- Device
- Software
Waveform virtual instrumentation software
Setting oscilloscope
Change probe setting
(Necessarily if you use probe not 1:1)
- Hit setting mark on the upper right corner of the channel window.
- Attenuation : 10X (depends on the probe type you are using)
Main screen in Oscilloscope mode.
Tweak with the division setting
-
Baselets you decide the time length per one division on X axis. -
Offsetchanges the position of the each channel wave. (You may also click & drag triangular handle on the left corner of the black screen) -
Rangedecides voltage range per one division on Y axis.
Set a trigger
-
Select sourcewhich channel you wanna use as a triger. -
Select conditionRising will do in most cases. -
State
voltage levelthat will identified as a trigger (you may also grab triangular handle on the right corner of the black screen)
Set to DC mode
To look into absolute value of voltage level, Discovery board should be set to DC mode.
Make sure that the blue tab is on DC side.
Measuring
150ms cycle of measuring and sending out data could be seen at this point.
Sensor Tx fires, then Serial Tx sends some kind of data to PC.
Take a bit deeper look on sensor part…
When the Tx set to HIGH, Rx signal bumps up at first but then slowly restore 2.5V which is the original voltage at point A in diagram below.
Then as the Tx set to LOW, Rx drops but gradually stabilise around 2.5V again.
The restoration of the voltage varies depending on the conductive property of two electrodes connected at the end of sensor Tx and Rx lines (Virtual capacitor in the diagram).
