There are times when you want to view both input channels at the same time, but neither provides a suitable trigger. In this example, when we trigger on Channel 1, the Channel 2 trace is unstable.

Unfortunately, if we trigger on Channel 2, the Channel 1 trace is unstable.

TekScope helps eliminate this problem. If you have a third signal that provides a stable trigger for both channels, hook it up to the DMM inputs, and set the "Trigger Source" to "Ext Trig" in the trigger menu.

When using an external trigger, you can set the trigger level to either 2 V or 200 mV. The 2 V setting is perfect for TTL control signals, and the 200 mV setting provides a good approximation of a zero crossing for triggering on the AC line voltage.