The default trigger mode is for edge triggering. Other trigger modes are explained in the Trigger Menu section.
Auto
Allows the scope to free-run and constantly collect data without waiting for a trigger event.
ChA
Forces the scope to wait on a trigger event on channel A defined by the other trigger controls before the display is updated.
ChB
Forces the scope to wait on a trigger event on channel B defined by the other trigger controls before the display is updated.
Ext
Forces the scope to wait on a level sensitive external trigger event. When this option is selected, the +ve/-ve button is replaced with a High/Low button (shown below).
This will cause the scope to trigger when the external trigger input signal is above or below the external trigger level. Please note that this option uses the right hand BNC connector with the green LED. Setting the external trigger configures the right hand BNC connector as an input. Consequently, the signal generator output is not available when the DS1M12 is using an external trigger source. Selecting Ext trigger when the signal generator output is active will stop the signal output.
The external trigger voltage must be in the range -3.5V to 3.5V.
Select a rising or falling edge event to trigger on by selecting "+ve" (rising edge) (A "+" on the display indicates +ve edge triggering)
or "-ve" (falling edge) (A "-" on the display indicates -ve edge triggering).
Use the "Trigger Level" buttons to set the desired trigger level voltage. The trigger level is shown as an arrow with a "T" to the right of the oscilloscope screen and is displayed numerically above the plot. The colour of the "T" arrow matches the colour of the trace that has been selected as the trigger source. If Ext trigger is selected, the "T" arrow colour matches the channel A trace.
When channel A is selected as the trigger source, the trigger line marker on the display is a blue line. If channel B is selected as the trigger source, the trigger line marker is red. For an external trigger there is no line.