Lambda SR1, Operation Manual, Page: 41 / 317

SR1 Operation 41
© 2014 Stanford Research Systems
Bursts the lo amplitude is fixed at zero.
Burst Period controls the duration of triggered bursts and the total on/off period for Timed and Shaped
bursts.
Burst Duty Cycle controls the fraction of the burst period during which the generator output is at the hi
amplitude.
EQ Controls
Certain waveforms can have their amplitudes scaled as a function of frequency according to the
information contained in an
EQ File . EQ files are XML files which specify a relative frequency response
as a function of frequency by either interpolating a table of (frequency, response) pairs or by calculation
from a set of pole and zero locations. The structure of EQ Files is detailed in the
File Reference section.
Use the button to open a file dialog to specify the EQ File. Check the Invert EQ box to have the
amplitude scaled by the inverse of the EQ file response. Waveforms that are capable of being used with
EQ files will have an "EQ" checkbox in their waveform tab. This box must be checked for EQ to be active
regardless of whether an EQ file is selected in the file selection control. When an EQ file is selected and
the checkbox is checked the amplitude control in the waveform tab will continue to show the constant
user-selected waveform amplitude, however, the Total Channel Amplitude control will display the
amplitude with the EQ response included.
2.3.1.1 Analog Generator Units
The amplitude and frequency of generator waveforms can be specified using a variety of units all of which
are useful in different audio test scenarios. Because of the large number of waveforms that SR1 can
generate and because it's useful to define amplitude in a way that simplifies the coupling between the
details of the waveform and its amplitude, SR1 uses the following two conventions for analog generator
amplitudes:
1. Analog generator amplitudes, regardless of the waveform or the units they are expressed in, refer to
the peak value of the waveform. When waveforms are combined in the generator, the amplitudes add
simply, regardless of the phase relation of the waveforms.
2. RMS units always, regardless of waveform, have the same relation to peak units that they do for a
sine wave.
Thus, a square wave with instantaneous amplitude of ±1V is said to have an amplitude of 1 Vp, or .707
Vrms even though this is not the actual value of the RMS amplitude derived from a computation. While
this may seem counterintuitive it simplifies the specification of amplitude units and is the convention
used by most audio test equipment.
The following table describes the units available for setting the amplitude of analog generator waveforms.
Unit Description
Vp Volts Peak, or simply volts. (The p is added to reduce ambiguity with other volt-oriented
units) An analog waveform with an amplitude of 1 Vp has an instantaneous peak value of 1
Volt.
Vrms A sine wave with an amplitude of 1.414 Vp has an RMS amplitude of 1 Vrms. In SR1,