Programming the Alternate trigger Mode
Introduction to Alternating Triggers
Alternating triggers on an oscilloscope can be used to
view and analyze two asynchronous signals at once. This is
very useful in cases where you need to monitor multiple
signals that are not coordinated in time, but you would
still like to view them on the same screen concurrently.
Signals can also be viewed in this way when their
frequencies are very different. For instance, on channel
can be set to view a 10 Hz signal while the other channel is
setup to monitor a 10 MHz signal. Extra care must be
taken when using this mode because the signals on the
display are not time coordinated.
To programmatically setup alternating trigger mode
you need a DS1000E series oscilloscope with up to date
firmware. You also need a PC with UltraSigma
communication software installed as well as a USB cable.
To get started power on the oscilloscope and
connect the 2 asynchronous signals to be used for testing.
We are using a 10 MHz sine wave on channel 1 and a 10
Hz square wave on channel 2 in this example.
First, in the storage menu select FACTORY settings
and push LOAD. This will reset the instrument to the initial
state. Then, to complete the setup, connect the DS1000E
series scope to your computer over USB and open
UltraSigma on the PC.
Setting up alternating triggers
Use UltraSigma to send these commands to
setup alternating trigger. Right click on the Online
Resource in UltraSigma that matches the instrument we
want to program and select SCPI Panel Control from the
pop up menu. This opens the window in Figure 2. Now we
are ready to program the instrument. First, leave the
*IDN? Command in the text line and click SEND & READ. In
the window below you should see the instrument’s
response. Then, send these commands in order clicking
SEND COMMAND after each one:
Note that you can set different time scales, trigger levels,
and trigger modes for each channel. Alternating trigger does
not have a true normal mode. There must be an occurring
trigger on at least 1 of the channels else it will switch to an
You can add measurements on the front panel as we did in
Figure 3 or request them over the bus using these commands:
After the first command click SEND COMMAND. After the
command that ends in a “?” click SEND & READ. In this case the
instrument responds with a value (1E7 = 10 MHz).