Lambda SR1, Operation Manual, Page: 110 / 317

SR1 Operation Manual 110
© 2014 Stanford Research Systems
control to select which generator will be the source of triggers. Only certain
waveforms generate triggers. See the Analog and Digital Generators section for
more information about generator triggers.
Digital Audio Block Selects the digital audio carrier "Z Preamble" (the beginning of a block) as the
trigger source. This option is only allowed when the analyzer source is set to
digital audio.
External Burst A,B Selects the burst as the trigger source.
The "Input Channel" and "Other Channel" triggers are level triggers, i.e. they trigger when the selected
signal passes through a level with a specific polarity chosen with the "Level" and "Polarity" controls. All
the other trigger sources are "binary"– they either occur or not.
Trigger Indicators
The two trigger indicators on the speedbar at the top of the SR1 screen flash green when the
corresponding analyzer is triggered. When an analyzer's trigger is enabled and the corresponding
analyzer is waiting for a trigger, the indicator is drawn with a yellow background.
2.4.1.1 Analyzer Units
The relation between various amplitude units in SR1 is always fixed at the same ratio that applies to a
sinewave. This can cause some confusion due to the fact that in normal usage an amplitude of 1 Vrms
implies not just a magnitude and unit of measurement, but a
method of measurement, i.e. an rms
integration over the waveform. In SR1 this is not the case, the measurement method is specified
separately and the units of measurement always have the same fixed sinewave relationship. An example
will help to clarify this. Consider the following square wave:
With an RMS voltmeter, the square wave shown would have an amplitude of 1 Vrms. With a peak-
responding meter, the square wave would be found to have an amplitude of 1 Vp or 2 Vpp. However, with
SR1, things are slightly more complicated in that it's necessary to know the measurement method as
well as the units to correctly interpret the answer. If SR1's Time Domain Detector was configured for and
RMS response and the amplitude units set to Vrms, SR1 would perform the RMS amplitude calculation
and display an answer of 1 Vrms. However, if the units of the answer were changed to Vp, the answer
would be 1.414 Vp because that's the sinewave relationship between Vp and Vrms. Likewise, if the Time
Domain Detector is configured for Peak response SR1 will display a result of 1 Vp, but if the units of the
display are changed to Vrms the display will read 0.707 Vrms.