Lambda SR1 Operation Manual

SR1 Audio Analyzer

Operation Manual

Stanford Research Systems

Audio

Revision 3.0.0 January, 2014

Distribution in the UK & Ireland

Lambda Photometrics Limited

Lambda House Batford Mill Harpenden Herts AL5 5BZ United Kingdom

E: info@lambdaphoto.co.uk W: www.lambdaphoto.co.uk T: +44 (0)1582 764334 F: +44 (0)1582 712084

Characterisation, Measurement & Analysis

SR1 Operation Manual2

Table of Contents

Foreword 0

Part I Getting Started

................................................................................................................................... 61 Unpacking and Safety

................................................................................................................................... 8

2 Manua l Revision History

................................................................................................................................... 9

3 Overview

................................................................................................................................... 13

4 User Interface

................................................................................................................................... 19

5 A Quick Example...

Part II SR1 Operation

................................................................................................................................... 281 File Menu

.......................................................................................................................................................... 29Save SR1 Configuration

.......................................................................................................................................................... 30

Save Partial Configuration

.......................................................................................................................................................... 31

Load Configuration

.......................................................................................................................................................... 32

Print SR1 Scre en

.......................................................................................................................................................... 33

Print Setup

................................................................................................................................... 342 Edit Menu

................................................................................................................................... 35

3 Panels Menu

.......................................................................................................................................................... 36Analog Gene rator Panel

......................................................................................................................................................... 41

Analog Generator Units

......................................................................................................................................................... 43

Analog Generator Wav eforms

.......................................................................................................................................................... 57

Digital Ge nerator Panel

......................................................................................................................................................... 60

Digital Gener ator Units

......................................................................................................................................................... 62

Digital Gener ator Wavef orms

.......................................................................................................................................................... 76

Analog Inputs Panel

.......................................................................................................................................................... 79

Digital I/O Panel

.......................................................................................................................................................... 87

Channel Status Panel

.......................................................................................................................................................... 90

Use r Status Pane l

.......................................................................................................................................................... 91

Sw e ep Pane l

.......................................................................................................................................................... 98

Settling Panel

.......................................................................................................................................................... 100

Monitors Pane l

.......................................................................................................................................................... 102

Multitone Pane l

.......................................................................................................................................................... 105

Clock Reference Panel

................................................................................................................................... 1074 Analyzers Menu

.......................................................................................................................................................... 108Com m on An alyze r Features

......................................................................................................................................................... 110

Analyzer Units

.......................................................................................................................................................... 115

Time Domain Detector

.......................................................................................................................................................... 127

FFT (Single Channel)

.......................................................................................................................................................... 141

FFT (Dual Channel)

.......................................................................................................................................................... 157

THD Analyze r

.......................................................................................................................................................... 161

IMD Analyze r

.......................................................................................................................................................... 165

Multitone Analyz er

.......................................................................................................................................................... 171

Histogram Analyzer

.......................................................................................................................................................... 175

Octave Analyze r

.......................................................................................................................................................... 177

Jitte r Analyze r

.......................................................................................................................................................... 183

Dig it iz e r

3Contents

................................................................................................................................... 1915 Displays Menu

.......................................................................................................................................................... 192Graph

......................................................................................................................................................... 199

Trace Calculator

.......................................................................................................................................................... 202

Bar Ch ar t

.......................................................................................................................................................... 205

Dig itiz e r Di s p la y

.......................................................................................................................................................... 212

Other Dis play M enu Options

................................................................................................................................... 2136 Tools Menu

.......................................................................................................................................................... 214Preferences Panel

.......................................................................................................................................................... 220

Eve nts Panel

.......................................................................................................................................................... 226

Switcher Configuration Panel

.......................................................................................................................................................... 230

Hardware Status

.......................................................................................................................................................... 231

Ne tworking

......................................................................................................................................................... 231

Network Setup

......................................................................................................................................................... 232

Netw ork Places

......................................................................................................................................................... 233

Map Netw ork Drive

......................................................................................................................................................... 233

Remo ve Ne tw o rk Driv e

......................................................................................................................................................... 234

Share SR1

.......................................................................................................................................................... 236

Compute r Functions

......................................................................................................................................................... 236

Pr inters Panel

......................................................................................................................................................... 237

Eje ct Dr iv e

......................................................................................................................................................... 237

Pow er Options

......................................................................................................................................................... 238

Date Time

......................................................................................................................................................... 238

Virtual Keyboard

......................................................................................................................................................... 238

Updating SR1

................................................................................................................................... 2417 Automation Menu

.......................................................................................................................................................... 242Remote Inte rface Panel

.......................................................................................................................................................... 243

Scripting Window

.......................................................................................................................................................... 252

Learning Mode

................................................................................................................................... 2538 Quick Measurement Menu

.......................................................................................................................................................... 254Setup Panel

.......................................................................................................................................................... 255

SNR Pan e l

.......................................................................................................................................................... 257

Re ference Panel

.......................................................................................................................................................... 259

Level Panel

.......................................................................................................................................................... 261

THD+N Pa ne l

.......................................................................................................................................................... 263

Frequency Res ponse Panel

.......................................................................................................................................................... 265

Distortion Pane l

.......................................................................................................................................................... 267

IMD Panel

.......................................................................................................................................................... 269

Crosstalk Panel

.......................................................................................................................................................... 271

Interchannel Phase Panel

.......................................................................................................................................................... 273

In/Out Phas e

.......................................................................................................................................................... 275

Automated Measurements and Reports

................................................................................................................................... 2789 Setups Me nu

.......................................................................................................................................................... 279Analog-Analog

.......................................................................................................................................................... 281

Analog-Digital

.......................................................................................................................................................... 283

Digital-Analog

.......................................................................................................................................................... 285

Dig it al -Di gi ta l

.......................................................................................................................................................... 287

Digital IO

................................................................................................................................... 28810 Help Menu

Part III SR1 Reference

291

................................................................................................................................... 2911 Front Panel Description

SR1 Operation Manual4

................................................................................................................................... 2932 Rear Panel Descritpion

................................................................................................................................... 296

3 Specifications

................................................................................................................................... 305

4 Filter Reference

................................................................................................................................... 306

5 File Reference

................................................................................................................................... 310

6 Hardw are Reference

Index 312

Part

Getting Started

Audio

SR1 Operation Manual6

1 Getting Started

1.1 Unpacking and Safety

Removing the Instrument From Its Shipping Container

Use care in removing the instrument from its shipping container. The SR1 weighs approximat ely 50 lbs, and can be awkward to handle while being removed from the box. In partic ular, please tak e care that the front panel LCD sc reen is not damaged while unpac king. Retain the original packing materials in case the unit ever needs to be returned for service.

Connecting The Power Cord

Your SR1 was shipped with a power cord appropriate to your location. SR1 operates from a 100V, 120V, 220V or 240V nominal AC power source with a line frequency of 50 or 60 Hz. Before connecting the power cord to the rear panel power entry module, please ensure the the LINE VOLTAGE SELECTOR card, located in the rear panel fuse holder, is set so that the correct AC input voltage value is vis ible. The fuse rating should also be checked t o see if it matches the line voltage setting. For 100V/120V operation a 4A fuse is used. For 220V/240V a 2A should be installed. The instrument has a 3-wire power cord. Be sure to connect it to a properly grounded outlet t o guard against elect rical shock.

After connecting the power cord to an AC power source, the unit can be turned on by pressing the power button at the lower left of the front panel. The green power LED above the power button illuminates to indicate the unit is on. After turning the power on the unit will take about 50 seconds to run through its boot-up sequence before it is ready for use.

Safety

Dangerous voltages, capable of causing injury or death, are present in this inst rument. Use extreme caution whenever the instrument cover is removed. Do not remove the instrument's cover while the power cord is connected to a live outlet. Do not expose the instrument to rain or exc essive moisture. Do not attempt to disconnect the internal cooling fans or block the fan vents.

Service

Refer all servicing to qualified, SRS-authorized service personnel. Do not attempt to substitute parts or perform any unauthorized modification to the instrument. Contact SRS for inst ructions on how to return the ins trument for authorized service, calibration, or adjus tment.

Stanford Research Systems 1290-D Rea mw ood Ave. Sunnyvale, CA, 94089 USA

hone 408.744.9040

email info

thinksrs.com

web www.thinksrs.com

Getting Started 7

SR1 Operation Manual8

1.2 Manual Revision History

No part of this manual may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system without permission in writing from Stanford Research Syst ems, Inc.

Manua l Revision History

Version Date Author Comments

1.0 1/06 jahan Original Version

2.0 7/09 ajm Preliminary Version shipped with first SR1s

2.1 10/09 ajm 2nd Preliminary version

2.2 12/09 ajm Complete Through Tools Menu

2.3 1/10 ajm Complete Manual

2.4 3/10 ajm For SR1 v 1.1

2.5 3/10 ajm Minor Printing Corrections

2.6 5/10 ajm Updated for SR1 v1.1.6

2.7 7/10 ajm Updated for SR1 v1.2

2.8 6/11 ajm Updated for SR1 v1.4

3.0 1/14 ajm Updated for SR1 v2.1.13

Windows is a trademark of the Microsoft Corporation

Apache Xerces

This product includes software developed at The Apache Software Foundation (http:/ /www.apache.org/).

Portions of this software were originally based on the following:

NI-De vice

FastReport

Getting Started 9

1.3 Overview

SR1 is versatile and complex instrument capable of making a wide a variety of precision audio measurements in both the analog and digital domains. The following is a brief introduct ion to t he different pieces of SR1 and their capabilities.

Measurement Setups

SR1 includes pre-configured setups for many common audio measurements. To get up and running quickly, see the Setups Menu

Generators

SR1 contains precise and flexible analog and digital audio generators. Eac h generator is built around several core waveforms which can be either generated individually or combined in the generator and output as a composit e signal. For the Analog Generator, the core waveforms include Sine, Low-Disortion Sine, Phased Sine, Noise, USASI Noise, Squarewave, Ramp (triangle), FFT Chirp, Multitone, Arbit rary, and Constant (offset). The analog generator can be output either as a balanced or unbalanced signal and ouputs a maximum peak output voltage of 20 V (unbalanc ed) or 40 V (balanced).

The Digital Generator offers the same core waveforms as the analog generator and additionally offers a number of waveforms optimized for digital interface test ing including Digit al Constant, Digital Counter, Walking Bits, and a J-test waveform designed to test the jitter susc eptibility of devices.

Analog Inputs

SR1 offers both balanced and unbalanced analog inputs with full scale input ranges from 160 Vrms down to 62 mVrms. SR1's analog inputs are autoranging, meaning that for most input signals, the analyzer automatically s ets the input range without any user interaction.

Digital Audio Inputs and Outputs

SR1 has 2 sets of XLR and BNC connectors and is c ompatible with both consumer and professional digital audio signals from 50 mVpp up to 10.2 Vpp. All significant parameters of the digital audio carrier signal are measured including s ignal amplitude, digital audio effective sampling frequency, and input/ output delay. Status bit s are fully decoded in both the the professional and consumer standards. User bits are also display ed in raw binary format.

Several impairment signals can be applied to the output digital audio carrier inc luding Common Mode Sinewave, Normal Mode Noise, and Jit ter. Jitter waveforms include Sine, Square, Noise, and Bandpass Noise with a peak jitter amplitude of ~13UI.

Analyzers

There are 8 different types of Analyzers in SR1, s ummarized below.

Time Domain Detector Makes wideband amplitude, ratio, and THD+N measurements. The time

domain detector signal chain includes bandpass or notch filters, bandwidt h limiting filters, and a variety of different weighting filters. Peak , RMS and Quasi-Peak responses are selectable

FFT (1 ch) Provides single-channel FFT functionality.Measurements inc lude power

spectrum, time record, phase. Both zoom (changing the FFT frequency range) and heterodyne (moving t he FFT frequency range) are included.

FFT (2 ch) Provides dual-channel FFT functionality.Meas urements include power

spectrum and time record for both channels, plus frequency response

SR1 Operation Manual10

(transfer func tion), and interchannel phase. Zoom (changing the FFT frequency range) is supported in the dual-channel analy zer.

THD Ana lyze r Makes frequency selective Total Harmonic Distortion (THD) measurements,

both ratio and absolut e. Includes the ability to measure only selected harmonics.

IMD Analyzer Makes st andard Intermodulation Distortion measurements including

SMPTE/DIN, CCIF (difference frequency), and DIM/TIM.

Multitone Analyzer Makes single-shot multitone measurements allowing fast measurements of

common audio parameters including noise, distortion, and level.

Jitter Analyze r Measures the jitter of the digital audio c arrier in both the time and frequency

domain including variable high and low pass filtering.

Histogram Analyzer Creates histograms of the analog and digital audio input s ignals.

Octave Analyzer Displays 1, 1/3, and 1/12 fractional octave spectra.

Each type of analyzer has a c orresponding panel with the appropriate controls for that analyz er and readouts for the analyz er's measurements. At any instant, there are two active analy zers, designated A0 and A1. The user can select the ty pe of A0 and A1 from any of the allowed analyzer types. Each analyzer has c ontrols which set the input domain to analog or digital audio and s elect the appropriate input c hannel.

For analog inputs SR1 offers an additional choice between two Analog-to-Digital c onverters, each optimized for different meas urements . The high-bandwidth (Hi BW) 16-bit ADC operates at a fixed sampling rate of 512 kHz. The high-resolution (Hi Res) ADC is a 24-bit converter which operates at fix ed sampling rates of 128 kHz and 64 kHz and and variable rates which can be sync hronized with the digital audio output or input s ignal to perform cross-domain measurements.

Sweeps and Free Run

SR1 operates in two different measurement modes: free-run and sweep. In free-run mode the analyzers make continuous measurements and continually updates the measurement results on the analyzer panels.The second mode, sweep mode, requires that several options be s et. First , a sweep source must be configured which determines whether SR1 will be sweeping an internal parameter (e.g. generator frequency) over a specified range, an externally measured parameter (e.g. input frequency), or at regular time intervals. Once the s weep source is configured the user must s elect the measurements (up to 6) that will be recorded during the sweep. Swept measurements mus t be settled to be included in the sweep meaning that t he transient variability of the measurement must drop below a user set value before being included in the sweep result. Sweep sources and data are setup on the Sweep Panel

, while

Settling parameters are set in the Settling

panel.

Displays

Three different types of displays are available for graphically displaying measurement data. The graph is the main display ty pe and is capable of displaying many different live and off-line data t races both. Graphs include cursors for reading out absolute and delta values, the ability to export to bitmap and Windows Metafiles, movable onscreen annotations, and a variety of data calculations (smoothing, linearit y, maximum and minimum, etc.) for manipulating data. The Bar Chart

is a simpler display optimized for displaying a single measurement value which reports the instantaneous value of the measurement as well as maximum, minimum, and standard deviation. The Digit izer Display

is designed to work with the optional digitizer and displays various meas urements calculated by the digitiz er including full-color eye diagrams.

Getting Started 11

Digitizer (Optional)

The optional digitizer digitizes the digital audio carrier signal at an 80 MHz s ampling rate. The digitizer calculates the overall clock rate of the signal as well as jitter as a function of time and probability density for pulse width, pulse amplitude, input amplitude, and jitter amplitude. The digitizer als o calculates the s pectra of both the carrier signal as well as the jitter signal. Finally the digitizer calculates an eye diagram which shows the probability of the carrier signal as a function of amplitude and time. The off-line measurements made by the digitizer complement the real-time jitter measurement capabilities of the Jitter Analyzer.

Remote Interfacing

SR1 Supports a variety of remote interfaces:

IEEE-488.2 (GPIB)

SR1 has a rear-panel IEEE-488 connector and fully supports the IEEE-488.2 standard. All instrument features c an be set and queried from the remote interface.

Serial

GPIB c ommands may also be sent over the rear-panel serial connec tor which supports baud rates up to

115.2 kBaud.

TCP/IP

GPIB c ommands may also be sent over a TCP/IP network via the rear-panel ethernet connector. SR1 follows the VXI-11 standard for the transmission of commands over TCP/IP.

COM

SR1 is fully COM enabled allowing applications such as Visual Basic to set and query instrument internals. COM enabled applications may also control and query the instrument remotely over ethernet. Not that firewall settings may need to changed to fully enable this functionality .

SR1 Operation Manual12

Getting Started 13

1.4 User Interface

The SR1 audio analyzer user interface is based on software that runs on the Microsoft Windows operating system. As such, the basic user interface, based on standard Windows menus and controls, should be familiar to most users who have used Microsoft Windows. The s ame software that runs on the instrument is available for free download from Stanford Research Syst ems (www.thinksrs.com

) and can be run on any W indows PC. While no measurements can be made while running on a PC, this mode is perfect for offline viewing of saved datafiles or simply becoming familiar with the software.

Like all Windows software, operating SR1 requires a point ing device and a means of entering text and numeric data. The instrument provides several options depending on the intended environment.

External Mouse and Keyboard Control

SR1 can be used with an external mouse and keyboard. The mouse and keyboard must be connect ed to the rear-panel connectors before the instrument is turned on to be properly recognized by the instrument. Operation with an external mouse and keyboard is convenient when SR1 will be used in a benchtop environment.

Using the Trackpad

For situations where it's inconvenient to use an external mouse (e.g. rac kmount), SR1 has a front-panel trackpad which can be used as a pointing device. (Note that the trackpad is always active, even when an external mouse is connected.) To use the trackpad, drag your finger over the surface of the pad to move the cursor on the s creen. To "left-click" gently tap your finger. To "double-click" tap your finger twice. Finally, to "right-click" tap your finger in the upper-right triangle (colored in a light er shade of gray).

Using the Front-Panel Keypad

The front-panel keypad provides a convenient way to enter numeric values as well to access some commonly used SR1 functions without having to reach for the mous e or keyboard.

SR1 Operation Manual14

Standard Function of Keypad Keys

Key Function

Nume ric Entry Ke ys

Numbers 0-9 Enters the c orresponding digit at the current cursor position.

. (Decimal Point) Enters the decimal point at the c urrent cursor position.

± Changes the sign of the number in the current entry field.

Backspace. Deletes the character to the left of the cursor.

Exp Inserts the "E" character at the current cursor position allowing entry in

scientific notation: e.g. 1.2E3

Esc Aborts numeric entry and returns the value in the selected field to the

previous value.

micro

inserts the "u" modifier at the cursor position, interpreted as x10-6.

milli

inserts the "m" modifier at the cursor position, interpreted as x10-3.

kilo

inserts the "k" modifier at the curs or posit ion, interpreted as x103.

Mega

inserts the "M" modifier at the cursor position, interpreted as x106.

Enter Finishes entering the new value.

Function Keys

Page Rotates through the seven pages of the page control on the SR1 screen.

(Tab Left /Right)

Moves the control with "focus" either to the next or previous control.

Sweep

Starts a Sweep. Equivalent to press ing the button on the speedbar.

Pause Pauses and resumes both sweeps and free-run mode. Equivalent to pressing

the

and but tons on the speedbar.

Run

Starts free-run mode. Equivalent to pressing on the speedbar.

Translate graph left/right. Once pressed, the keys will move the data in t he current graph left and right. Press "Esc" to exit this mode.

Zoom X-axis. Once press ed the keys will zoom the X-axis in and out. Press "Esc" to exit this mode.

AutoScale. Autoscales the X and Y ax es of the c urrently selected graph.

Max Moves the active cursor in the current graph to the position corresponding to

the maximum value displayed in the graph.

Cursor If the selec ted graph cursor is off, this key turns cursors on. If they are on,

this key toggles the active cursor between the two cursors.

Alt Selec ts the Alt function (written in Green above the keys) for the keypad

keys.

Alt-Function Keys

Menu Moves focus to the main menu. Once Menu is pressed, the knob and enter

keys can be used to acces s the main menu s elections without us ing a pointing devic e.

Sticky Normally, the knob varies whatever control on the screen currently has focus.

Press Sticky to "Stick" the knob to the current control. Even when focus is moved to a different control the knob continues to modify the sticky control. The sticky control is drawn with a

yellow background. Press sticky again to

Getting Started 15

exit sticky mode.

Local Upon receipt of a command from one of the remote interfaces SR1 is placed

in "Remote" mode. Using this key returns the unit to local c ontrol.

Ref AutoReference. The contents of the currently focused control is examined. If

it is a frequency, the frequency is moved to the frequency reference of the selected analyzer. The analyzer, A0 or A1 is selected by press ing the

keys after pressing "Ref". If the contents of the currently focus ed window is not a frequency then the contents of the A and B levels for the selected analyzer will be transferred to the dBrA and dBrB references (either analog or digit al, depending on the analyzer input.)

Hex, Hex Digits A-F

Hex Entry mode. Places a "0x" charact er in the c urrently focused c ontrol to begin hexadecimal entry. In this mode, the "A", "B", "C","D","E", and "F" characters above the micro, milli, kilo, meta, Exp, and Page keys are act ive allowing the entry of a hexadecimal value. Hex Entry mode is terminated when "Enter" is pressed.

Generator

After pressing this key press to open the analog generator panel or

to open the digital generator panel.

Analy zer

After pressing Analyzer press to open t he A0 panel or to open the A1 panel.

Alpha Calls up the virtual keyboard.

Translate graph up-down. Once press ed, the keys will move the data in t he current graph up and down. Press "Esc" to exit this mode.

Zoom Y-axis. Once pressed the keys will zoom the Y-axis in and out. Press "Esc" to exit this mode.

Autoscale X, Y

After pressing the key, use t he keys to select autoscale of either the the X or Y axis.

Min Moves the active cursor in the current graph to the position c orresponding to

the minimum displayed value in the graph.

Help Brings up the online help.

Using the Knob

Turning the knob modifies the currently focused control. If the control is a unit entry control, the knob increments and decrements its value with an appropriate resolution. If the control is a drop-down list the knob cycles through the entries in the list. Three different knob acceleration profiles c an be selected from the preferences panel

. A control can be selected as "Sticky" in which case the knob will continue to control it even though focus is given to another control. When cursors on a graph are active the knob controls the active cursor position.

Using the Virtual Keyboard

For situations where it's necessary to enter text into a cont rol and an ext ernal key board is not available the Virtual Keyboard can be selected from the SR1 keypad

or from the Tools Menu. The virtual keyboard offers the full functionality of a standard PC keyboard but c an be operated with just a mouse or the trackpad.

SR1 Operation Manual16

Keyboard Shortcuts

A number of keyboard shortcuts are available (us ing either an external keyboard or the virtual key board) to simplify the execution of common functions.

Key Sequence Action

<Ctrl> 1-7 Selec t the designated page (1-7) on the page control as the active page.

<Ctrl> D Opens the digital generator panel.

<Ctrl> G Opens the analog generator panel.

<Ctrl> I Opens the digital i/o panel.

<Ctrl> A Opens the analog inputs panel.

<Ctrl> M Opens the monitors panel.

<Ctrl> W Opens t he sweep controller panel.

<Ctrl> T Opens the scripting window.

<Ctrl> [ Opens the A0 analyzer panel.

<Ctrl> ] Opens the A1 analyzer panel.

F4 Auto-reference analyz er A0. Moves the current A0 level A and B values to the dBrA

and dBrB reference values.

<Ctrl> F4 Auto-referenc e analyzer A1.Moves the current A1 level A and B values to the dBrA

and dBrB reference values.

F12 Emergenc y shutoff. Turns off all channels of the analog and digital generators.

<Ctrl> F12 Restore generators. Turns on generator channels that were turned off with F12.

Scripting Window Shortcuts

<Ctrl> S Save the current script.

<Ctrl> O Open a script.

<Ctrl> N Create a new script.

<Ctrl> C Copy selected text to the clipboard.

<Ctrl> X Cut selected tex t and copy to the clipboard.

<Ctrl> V Paste clipboard text at the cursor location.

<Ctrl> F Brings up the dialog for finding text in the script.

<Ctrl> R Brings up the dialog for finding and replacing text in the s cript.

<Ctrl> P Prints the current script.

Getting Started 17

Unit Entries

The Unit Entry is a type of control used extensively throughout SR1 that allows entry of numeric data in a range of different unit s. The example below shows the generator amplitude control for example. W hen

the down-arrow

is clic ked, a the current value of the

entry is shown in the drop-down lis t expressed in each of the allowed units. Selecting a different unit makes it the current unit for subs equent entries. To enter a new value into a unit entry first click anywhere on the current text, and then enter a new numeric value followed by an optional modifier character. The allowed modifiers are:

Character Modifier Numeric Value

f femto

x10

-15

p pico

x10

-12

n nano

x10

-9

u micro

x10

-6

m milli

x10

-3

k kilo

x10

M mega

x10

G giga

x10

T tera

x10

(Note that the front-panel k eypad contains dedicated keys for the unit-modifiers just to the right of the Enter key.) To complete the entry press the "Enter" k ey on the front panel or an external keyboard. To abort the entry press the "Esc" key on t he keypad or keyboard.

Somet imes the precision of the value represented by a unit entry may exceed the number of digits displayed. To s ee the value of any unit entry displayed with full double precision hold the cursor over the unit ent ry— the full double precision value will be shown as a "hint."

Unit Displays

Unit Displays are the controls with a black bac kground and green text which are used to display measurement results and other quantit ies whose value can't be changed by the user. As with unit

entries , the units of the unit display can be changed by using the mouse or trackpad to click on the at the right of the control and select a unit from the drop-down list. Right-clic king the Unit Display brings up a menu which offers some more options:

SR1 Operation Manual18

Normally the Unit Display auto-selects the appropriate unit-modifier for the currently displayed value. For instance 1.2x10

-6

Vrms would be displayed as 1.2 Vrms. There are situations where it might be

desirable to lock the unit-modifier selection. For instance we might want the display to readout as

0.0012 mVrms. To do this, select the appropriate modifier from the right-click menu. Select "Aut o" from the right-click menu to return to normal operation.

The second feature offered by Unit Displays is selected in the bottom half of the right-click menu. In "Standard" mode, the Unit Display displays each new value that is sent to it . If one of the other modes are selec ted, the current value of the display is saved as the "reference" and subsequent updates are displayed as follows:

Mode Operation

Standard Each update to the Unit Display's value is displayed.Data is displayed in Green.

Max Updates are display ed only if they are greater than the reference value. When the

data exceeds the reference that data becomes the new reference value. Data is displayed in Re d.

Min Updates are display ed only if they are less than the reference value. When the

data is less than the reference that data becomes the new referenc e. Data is displayed in Bl ue .

Delta The difference between the update value and the reference value is displayed.

Data is displayed in Purple.

To reset the reference double-click the display .

Like unit entries, it is possible to s ee the value represented by a unit display with full double precision by holding the cursor over the unit display— the double precision value will be shown as a "hint."

Getting Started 19

1.5 A Quick Example...

In this example we'll use the analog generator to c reate a signal with a known amount of distortion and we'll use the Time Domain Detector to measure the distortion and the FFT analyzer to look at the distortion in the frequency domain. To begin, turn on SR1 and wait for the instrument to finish its s tartup sequence. No external cables will be necessary for this demo. Feel free to use the front panel trackpad and keypad keys to control the instrument, or if you've got an external mouse and key board you can those. We won't go into ex cruciating detail on how to select items and use the controls because they're standard Windows controls and their operation should be familiar.

Start out by using the speedbar at the top of the SR1 screen to open the Analog Inputs panel and the Analog Generator panel, and from the Analyzers menu, set Analyzer 0 to Time Domain Detec tor. Thes e three panels may automatically open when SR1 is powered up.

SR1 Spe edbar

Note that the icons for the Analog Inputs panels and the Analog Generator panel are both orange . SR1 uses orange to denote items associated with the analog domain and blue to denote items ass ociated with the digital audio domain. Most panels have color bars under the title of the panel indicating the domain associated with the panel.

The three panels y ou've jus t opened should look like this:

Now let's configure the instrument for this example. On the Analog Inputs panel, change the Input Source for both channels from BNC to GenMon. With the inputs set to GenMon the Ch. A analog input is directly connected t o the Ch. A generator output and the Ch. B analog input is directly connec ted to the Ch. B generator output. Leave the "Auto" box checked for each of the range c ontrols. With Auto Range on, SR1 automatically adjusts the range to the optimum value for the c urrent input signal. Note that the ranges are set to their minimum value (62.5 mVrms) and the Input Level indicators are showing blue (below half scale). That's because the generator hasn't been set up yet.

SR1 Operation Manual20

Take a look at the Analog Generator panel. We haven't selec ted any waveforms yet, so the tab cont rol at the bottom only contains the configuration tab. By default, the generator is in "Mono" mode which means that the same waveform will be output on the A and B channels . W e can adjust the channel amplitudes s eparately, but the waveform is the s ame. (In "Stereo" mode we can select different waveforms for A and B but we don't need to do that for this example.) Now press the "New" button on the Analog Generator panel. This brings up the menu of available waveforms. From the Sine submenu choose "Normal Sine". After the Sine waveform shows up in the tab control set an amplitude of 1Vrms. Note how the range c ontrols on the Analog Input panel both move to the 1 Vrms input range and the Input Level indicators turn green, indicating the ranges are optimally adjus ted. (The Input Level indicators are also visible at the bottom right of the SR1 screen.) Now we can add a little bit of distortion to t he signal. Pres s the "New" button again on the Analog Generator panel and once again select a "Normal Sine". This time set the frequency to 2 k Hz and the amplitude to 1 mVrms. We've just illustrated a key feature of the SR1 generator's architecture— the ability to combine several waveforms in the generator. The 1 kHz 1 Vrms signal and the 2 k Hz 1 mVrms signals are added in the generator. Using this technique an almos t infinite variety of waveforms c an be created in the generator to suit almost any test situation.

Now let's measure the properties of the signals just created. Look at the Time Domain Detector panel and change the source from Digital A to Analog A. The "Converter" field will read "HiRes" indicating that the analy zer is using SR1's 24-bit High-Resolution converter. The current s ampling rate for this converter, 64 kHz, is displayed in the "Fs" field next to the converter selection. SR1 uses two high quality analogto-digital converters (ADCs) for analysis of analog signals— a 24bit high-resolution converter that can operate over a variety of sampling rates and a 16 bit high-bandwidth converter that operates at a fixed sampling rate of 512 kHz giving the instrument an analog bandwidth of 200 kHz. The differences between the two converters will be discussed in detail later but for now we can leave the converter selection at "HiRes."

Press the

button at the top left of the screen to start the measurements. Note that the Status Indicator at the bottom left of the screen. SR1 operates in two distinct measurement modes. In "Free Run" mode, which we jus t started, all the analyzers make continuous measurements and cont inuously update the results on the analyzer panels and displays . This mode is us eful for benchtop ex ploration like we're doing now. "Sweep" mode is a more structured measurement mode in which the instrument sweeps a certain parameter and only measures data at certain defined values of that parameter. Sweep mode is more useful for repetitive testing to standards. We'll do a sweep at the end of this demo as an example. For now observe how in Free-Run mode the analyz er's level and amplit ude displays are continuously updated.

To measure the " distorted" sine signal we've c reated, select "THD+N Ratio" as the Measurement in the Time Domain Detector. Change the units of the Amplitude display to dB, and the three panels should appear as they do below:

Getting Started 21

When " THD+N" ratio is selected, the analyzer inserts a deep notch filter at the frequency of the fundamental. In this case, becaus e the notch filter is set to be tuned to the measured frequency, it is s et at the 1 kHz dominant frequency of our generator signal. The Time Domain detect or then performs an RMS integration of the remaining signal, which is distortion plus noise, and displays the ratio of that signal to the total amplitude of the input Note that the measured THD+N ratio is -60 dB. (1 mV / 1 V = 60 dB).

To show how much more SR1 brings to a standard distortion meas urement s elect the second analy zer (A1) as the FFT1 analyzer. W hen the panel is displayed, change the source of the Analyzer to "Other Analy zer". In this mode the FFT analyzer and the Time Domain Analyzer work as a team; the FFT analyzer looking at the notch filtered signal from the Time Domain Detector. Take a look at the information displayed on the FFT1 analyzer panel:

Like all analyzers t he input s ource is displayed at the upper left. The analyzer sampling rate is displayed at the upper right. Because we've connec ted the FFT analyzer to the output of the Time Domain Detector

SR1 Operation Manual22

the sampling rate for the FFT analyzer is also 64 kHz. Just underneath is the control for setting the number of FFT lines (resolution). The resolution can be set to values between 256 lines and 32k lines. Unlike most Audio Analyzers, SR1's FFT analyzer doesn't operate at a fixed frequency range from DC to Fs/2. The Bandwidth control allows s etting the meas urement range to Fs/2, Fs/4, etc., all the way down to Fs /2048. The full FFT resolution is applied to this narrower frequency range, which can be moved to any position in the range of DC to Fs/2 using the "S tart," "Center," and "End" controls. We will illustrate this shortly.

Averaging can be applied t o the FFT t o lower the shot-to-shot variation in the noise, or in some cases to actually lower the amount of noise. Select 5 averages in the "# Avgs" field to create a nice stable FFT display.

To display the FFT results we'll need to create a graph. Click on "Page 2" of the page control to give us

some room for the graph and click on the

icon to create a new graph. Maximize the graph with the standard maximize c ontrol in the upper right. Now we need to add some data to the graph. Clic k the "Plus" sign icon at the top left of the graph to add a trace to the graph. The "Add Trace" menu appears. Open the "A1 FFT" node to see the measurements produced by the A1 FFT analyz er.

Note that scalar measurements, like frequency or level, are denoted with the icon while vector

measurements like s pectra are accompanied by the

icon. Selec t "Power Spectrum", click ok, and the FFT will appear. Since we're looking at a very wide dynamic range, some logarithmic units will help. Click on the "Ymax " Unit Entry and change the Y units to " dBVrms". Now click the "Log" box in the X axis row to select a logarithmic X-axis. Click on the

icon (autoscale) on the graph speedbar to

autoscale the display. Now turn on the graph cursors by clic king the

icon. Use the knob or the

mouse to drag cursors as shown below. The graph should look like this:

Getting Started 23

Now we're ready to zoom in on a portion of the the distortion product s pectrum. Go back to Page 1 of the page control, and in the bandwidth control of the FFT analyz er selec t 500 Hz.In the "Center Frequency " field s elect 1 kHz. We're narrowing the bandwidth by a factor of 64, still using 1k FFT lines, and centering the new bandwidth on the notc hed out fundamental. Go back to Page 2, autoscale the spectrum, which should now look like this:

SR1 Operation Manual24

Note how more detail is resolved inside the notch. Go back to the FFT analyzer on page 1 and press the "Baseband" button to return the analy zer to it's full measurment range. We're now ready for the las t step in the demonstration.

Setting Up a Sweep

On page 1 click on the icon to open the sweep controller panel.W e're going to sweep the amplitude of our "distortion" sine wave and record the measured THD+N from the Time Domain Detector: Clic k on the Sweep Source button to bring up the sweep source selection menu:

SR1 has 3 main ty pes of sweep sources: Time Sweeps, where the s weep occurs at fix ed time intervals, Internal Sweeps, where the s weep occurs at fixed values of some internal parameter, and External Sweeps, where the sweep occurs at fixed values of some externally measured parameter. Since we're going to s weeping the amplitude of the sinewave we created in the generator, this will be an "Internal" sweep. Open the Internal node on the tree, and then open the AnlgGen (Analog Generator) node to show the associated parameters that can be swept. Note that there are two sine amplitudes and frequencies shown, Sine(0) and Sine(1). That's because we created two sinewaves in the generator. The first, Sine (0), refers to the 1 kHz fundamental. The second, Sine(1) is the "distortion" s inewave whose amplitude we're going to sweep. Double-click on ChA:Sine(1):Amp to select it and return to the sweep panel:

Getting Started 25

Selec t the start amplit ude as 100 uVrms and the stop amplitude as 100 mVrms. Leave the number of sweep steps at 30, but select "Log Step Size." Next we need to select that data that will be measured in the s weep. Up to 6 separate measurements can be recorded at each sweep point. Click on the Sweep Data "()..." to specify the sweep data. From the Sweep Data Selection menu, open the A0 node since the measurement we're going to record, THD+N, is made by the currently active Time Domain Detector on A0:

SR1 Operation Manual26

Selec t Analog THD Ratio A by double-clicking it. We're now ready to set up the graph to display our sweep.

Return to Page 2 of the page control. In the t race listing panel at the bottom of the graph unclick the Power Spec trum trace that we were looking at previously. Now use the "Plus" button at the top of the display to add another trace to graph. This time open the "Sweep" node and selec t "THD Ratio A". Selec t a log X-axis (to match the log sweep we just specified, and s elect dB as the Y-axis units with the unit ent ry controls. Select a Y axis range from -95 to -10 dB. Now start the sweep by pressing the "Sweep" button on the front panel. After a few seconds you'll see the results of the sweep:

This, of course, is exactly what we expect. At an amplitude of 100 uVrms, the THD+N is simply 20*log (100 uV/1V) = -80 dB. At the other of the s weep the the THD+N is 20*log( .1V / 1V) = -20 dB.

This quick example only scratches the surface of SR1's capabilities, but should give you a feeling for how the ins trument operates.

Part

SR1 Operation

Audio

SR1 Operation Manual28

2 SR1 Operation

2.1 File Menu

The File Menu contains options for saving and recalling instrument configurations and also for printing.

Save SR1 Configuration

Saves the entire inst rument s etup to a configuration file.

Save Partial Configuration

Saves the entire inst rument s etup to a configuration file.

Load Configuration Loads set up information from a configuration file.

Print SR1 Screen Prints the currently displayed screen to the currently selected printer.

Print Setup Displays the standard Windows Print Setup dialog allowing the selec tion of

an installed printer and paper options.

SR1 Operation 29

2.1.1 Save SR1 Configuration

Selecting File Save SR1 Configuration saves the entire instrument setup to an SR1 configuration file. Configuration files are XML files whose structure is detailed in the SR1 File Reference

. The default extension for configuration files is ".XML".All operating parameters, as well as the the pos ition of all panels and display s are recorded in the configuration file. After loading the file the instrument state will be exactly what it was when saved.

The trace data option governs how SR1 will save data stored in graphs. "Never Save" means that no graph data will be saved along with the configuration file. The file, in t his case, is a pure "settings" file. "Always Save" means that all graph data, including live measurements, will be saved with the configuration file. "Save if Offline" means that only offline graph data, such as reference curves or limits, will be saved with the configuration.

SR1 Operation Manual30

2.1.2 Save Partial Configuration

Selecting File Save Partial Configuration allows a choice of which portions of the ins trument setup will be saved to the SR1 configuration file. After selecting this option, the Save Partial Configuration dialog box is diplayed.

Selec t the portions of the instrument configuration to save and click "OK" to display the s tandard SR1 file save dialog box .

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Lambda SR1 Operation Manual

Specifications and Main Features

Frequently Asked Questions

User Manual