Big Features - Small Package! General System Features

LinearX Systems Inc • 9500 SW Tualatin-Sherwood Rd. • Tualatin, OR 97062-8586 USA • TEL: (503) 612-9565 • FAX: (503) 612-9344

www.linearx.com • [email protected]

Computer Aided Engineering & Measurement Systems

Big Features - Small Package!With a footprint smaller than a sheet of paper the LX500TM

contains an impressive array of powerful features and ca-pabilities unmatched in any analyzer this size and price.

Designed for maximum flexibility in both permanent andportable applications the LX500TM is powered by a single12VDC power source.

The small size and light weight of the LX500TM enables itto be carried by hand, tossed in a brief case, placed on adesktop, easily installed in a permanent engineering lab,or in a demanding production QC environment.

Featuring both Frequency Domain, Time Domain, and DualDomain versions the LX500TM supports a vast array ofdifferent measurement types, techniques, and methods.

Dual Analog Oscillators, Triple Multi-Function Inputs,Precision Noise Generator, Programmable Filter, exten-sive Bandwidth / Weighting Filters, Phase Meter, HighResolution Digital Signal Generator / Spectrum Analyz-ers, Digital I/O Control, and comprehensive Windows Ap-plication software are only some of the outstanding fea-tures and advanced capabilities offered by the LX500TM.

General System Features• Three Models: Frequency, Time, and Dual Domain versions• Very High Density Modular SIP Construction• Dual Outputs for individual Phase, Impedance, and Muting• Triple Multi Function Inputs: Bal, Unbal, LVP, 48V Phtm Power• Triple Monitor Outputs, plus External Generator Input• Input noise -120dBm, Max signal input +40dBm (77Vrms)• Digital Interface Control, 16 lines I/O on DB25M connector• All Calibration data stored in multiple Flash Memory• Microcontroller: 96MHz ARMTM Cortex-M3• USB Interface / Full speed 12MHz

Application Software Features• Windows Application software with USB driver• Multiplexed Measurements for single pass multiple curves• Processing Utilities, Math Operations, and Macro Script QC• 2D and OpenGL 3D graphics, polar x/y/z spatial plots• Support and extension of all previous LMS™ capabilities• Multiple LT360 Polar Turntable support

Frequency Domain Features• Frequency Range of 10Hz - 100kHz• Wide Dynamic Range of 140dB• Ultra High Performance Discrete MDAC architecture• Dual Low Distortion Oscillators & Noise Generator• Precision Phase Detector with High Noise Immunity• 8-Pole Programmable Filter: LP, HP, BP, BR• Extensive Bandwidth and Weighting Filters

Time Domain Features• High Resolution Data Width: 24 Bit Word Size• High Resolution Sample Depth: 4096 to 4,194,304 Samples• Multiple Sampling Rates: 216kHz, 108kHz, 54kHz, 27kHz• Synchronous Sampling on all Analyzer Channels• Reliable Internal Sampling Memory: 16MB PSRAM• Numerous Stimulus Types: Sine, MLS, Chirp, Complex, User

Applications• Audio System and Equipment Measurements• Acoustic System and Transducer Measurements• Sound Reinforcement System and Room Measurements• Single & Multiple Channel Polar Measurements• Electroacoustic Measurements: SPL, Voltage, Current• Multi Axis Vibrational Accel Measurements: X, Y, Z• Hearing Audiometry Testing: Left, Right, Reference• Low Signal to Noise Ratio (SNR) Measurements• QC Pass/Fail Production Line Testing

High Density Modular DesignThe construction of the LX500TM is based on a modular SIP architec-ture where the majority of the circuitry is placed vertically onSingle In-line Package (SIP) cards. This enables a veryhigh density design utilizing all three dimensionsof the internal chassis space.

The modularity enables eachcard to be pretested andcalibrated before assembly,and provides for modelvariations and convenientservice and replacement.

To ensure the ultimate insignal integrity and reliability,all modules are soldered in place.There are no internal mechanical connectorsor contacts which could cause signalintermittency in any circuit path.

The LX500TM contains no analog trim pots. Instead itutilizes entirely digital calibration and Flash Memorystorage of data. All data is secured via encryption,checksums, and unique individual module serial numbers. Over two dozen flash memory ICs within the unit permanently storeall of the calibration parameters and data, and can be recalibrated/updated as needed. The modules are calibrated and testedindividually via automated test equipment using a GPIB network controlled by software algorithms on a custom test fixture.

User UpgradabilityThe modular construction enables the user to upgrade one model version to another merely by adding various modules. Thesemodules are provided as an upgrade kit, and can be easily soldered into the mainboard with minimal skills. The image belowshows an existing Frequency Domain model, and the required 5 Time Domain module positions which would be filled.

OSCILLATORLOGIC

CONTROL

OSCILLATORLOGIC

CONTROLGEN

SOURCE

OUTPUT/INP-AMONITOR

EXTERNALGENERATOR

SOURCE/INP-BMONITOR

METER/INP-CMONITOR

INPUTSOURCE

INC

INB

INA FILTERSOURCE

NOISESOURCE

WEIGHTINGANSI FILTER

WEIGHTINGCOMM FILTER

BANDWIDTHHIGHPASS FILTER

BANDWIDTHLOWPASS FILTER

METERSOURCE

BAL/UNBAL9VDC LVP

48V PHNTM

BAL/UNBAL9VDC LVP

48V PHNTM

BAL/UNBAL9VDC LVP

48V PHNTM

OUTPUT-A

INPUT-A

EQUIVALENT BLOCK DIAGRAM(C)opyright 2010 LinearX Systems Inc

INPUT-B

INPUT-C

METERADC

12 BIT

METERDIGITAL24 BIT

METERADC

12 BIT

-70dBm/+26dBm40Ω/50Ω/150Ω/600Ω

CMRR 65dB

77V/+40dBm Max0.5uV/-124dBm100KΩ||100KΩ

CMRR 60dB


CMRR 60dB


CMRR 60dB

GEN

MTR

MTR

METERADC

12 BIT

SRC

SRC

SRC

GEN

OSC-A

IM-1:1

IM-1:4

OSC-B

FILTER

EXT

NOISE

DIGITAL

MTR

MTR

LINEDRIVER

MUTEPHASE

IMPEDANCE

OUTPUT-B

-70dBm/+26dBm40Ω/50Ω/150Ω/600Ω

CMRR 65dB

LINEDRIVER

MUTEPHASE

IMPEDANCE

INPUT GAIN- 20 / + 5010dB STEPS

DIGITAL 24b/216kHzSPECTRUM ANALYZER

DIGITAL 24b/216kHzSIGNAL GENERATOR




PINK NOISEFILTER

METER GAIN0 / +50

10dB STEPS

HP-10.0FILTER

HP-20.0FILTER

HP-22.4FILTER

HP-100FILTER

HP-400FILTER

ANSI-DFILTER

ITU-468FILTER

ITU-ARMFILTER

ANSI-AFILTER

ANSI-BFILTER

ANSI-CFILTER

F-CURVEFILTER

ITU-041FILTER

C-MSGFILTER

LP-10.0KFILTER

LP-20.0KFILTER

LP-22.4KFILTER

LP-30KFILTER

LP-80KFILTER

OSC IM1:1/4:1

OUTPUT DAC GAIN/ATTEN

+20/0/-20/-40

WHITE NOISEGENERATOR1Hz-250kHz

PROGRAMMABLEBP/BR/LPHP FILTERDACINT

DACINT

DACINT

DACINT

DACINT

DACINT

DACINT

DACINT

DACINTDACINT

DACINTDACINT

OSCILLATORANALOGPROCESS


INPUT GAIN- 20 / +50

10dB STEPS


PHASEDETECTOR

-40/+20dBm

PERIODCOUNTER

5Hz/200kHz

RMSDETECTOR

-40/+20dBm

RMSDETECTOR

-40/+20 dBm

INC

INB

INA

Time Domain Configuration

OSCILLATORLOGIC

CONTROL

OSCILLATORLOGIC

CONTROLGEN

SOURCE

OUTPUT/INP-AMONITOR

EXTERNALGENERATOR

SOURCE/INP-BMONITOR

METER/INP-CMONITOR

INPUTSOURCE

INC

INB

INA FILTERSOURCE

NOISESOURCE





METERSOURCE

BAL/UNBAL9VDC LVP

48V PHNTM

BAL/UNBAL9VDC LVP

48V PHNTM

BAL/UNBAL9VDC LVP

48V PHNTM

OUTPUT-A

INPUT-A


INPUT-B

INPUT-C

METERADC

12 BIT

METERDIGITAL24 BIT

METERADC

12 BIT

-70dBm/+26dBm40Ω/50Ω/150Ω/600Ω

CMRR 65dB


CMRR 60dB


CMRR 60dB


CMRR 60dB

GEN

MTR

MTR

METERADC

12 BIT

SRC

SRC

SRC

GEN

OSC-A

IM-1:1

IM-1:4

OSC-B

FILTER

EXT

NOISE

DIGITAL

MTR

MTR

LINEDRIVER

MUTEPHASE

IMPEDANCE

OUTPUT-B

-70dBm/+26dBm40Ω/50Ω/150Ω/600Ω

CMRR 65dB

LINEDRIVER

MUTEPHASE

IMPEDANCE







PINK NOISEFILTER

METER GAIN0 / +50

10dB STEPS

HP-10.0FILTER

HP-20.0FILTER

HP-22.4FILTER

HP-100FILTER

HP-400FILTER

ANSI-DFILTER

ITU-468FILTER

ITU-ARMFILTER

ANSI-AFILTER

ANSI-BFILTER

ANSI-CFILTER

F-CURVEFILTER

ITU-041FILTER

C-MSGFILTER

LP-10.0KFILTER

LP-20.0KFILTER

LP-22.4KFILTER

LP-30KFILTER

LP-80KFILTER

OSC IM1:1/4:1

OUTPUT DAC GAIN/ATTEN

+20/0/-20/-40



DACINT

DACINT

DACINT

DACINT

DACINT

DACINT

DACINT

DACINTDACINT

DACINTDACINT




10dB STEPS


PHASEDETECTOR

-40/+20dBm

PERIODCOUNTER

5Hz/200kHz

RMSDETECTOR

-40/+20dBm

RMSDETECTOR

-40/+20 dBm

INC

INB

INA

Frequency Domain Configuration

OSCILLATORLOGIC

CONTROL

OSCILLATORLOGIC

CONTROLGEN

SOURCE

OUTPUT/INP-AMONITOR

EXTERNALGENERATOR

SOURCE/INP-BMONITOR

METER/INP-CMONITOR

INPUTSOURCE

INC

INB

INA FILTERSOURCE

NOISESOURCE





METERSOURCE

BAL/UNBAL9VDC LVP

48V PHNTM

BAL/UNBAL9VDC LVP

48V PHNTM

BAL/UNBAL9VDC LVP

48V PHNTM

OUTPUT-A

INPUT-A


INPUT-B

INPUT-C

METERADC

12 BIT

METERDIGITAL24 BIT

METERADC

12 BIT

-70dBm/+26dBm40Ω/50Ω/150Ω/600Ω

CMRR 65dB


CMRR 60dB


CMRR 60dB


CMRR 60dB

GEN

MTR

MTR

METERADC

12 BIT

SRC

SRC

SRC

GEN

OSC-A

IM-1:1

IM-1:4

OSC-B

FILTER

EXT

NOISE

DIGITAL

MTR

MTR

LINEDRIVER

MUTEPHASE

IMPEDANCE

OUTPUT-B

-70dBm/+26dBm40Ω/50Ω/150Ω/600Ω

CMRR 65dB

LINEDRIVER

MUTEPHASE

IMPEDANCE







PINK NOISEFILTER

METER GAIN0 / +50

10dB STEPS

HP-10.0FILTER

HP-20.0FILTER

HP-22.4FILTER

HP-100FILTER

HP-400FILTER

ANSI-DFILTER

ITU-468FILTER

ITU-ARMFILTER

ANSI-AFILTER

ANSI-BFILTER

ANSI-CFILTER

F-CURVEFILTER

ITU-041FILTER

C-MSGFILTER

LP-10.0KFILTER

LP-20.0KFILTER

LP-22.4KFILTER

LP-30KFILTER

LP-80KFILTER

OSC IM1:1/4:1

MULTI DAC GAIN/ATTEN

+10/0/-10/-20/-30



DACINT

DACINT

DACINT

DACINT

DACINT

DACINT

DACINT

DACINTDACINT

DACINTDACINT




10dB STEPS


PHASEDETECTOR

-40/+20dBm

PERIODCOUNTER

5Hz/200kHz

RMSDETECTOR

-40/+20dBm

RMSDETECTOR

-40/+20 dBm

INC

INB

INA

Frequency & Time Domain Configuration

Model Versions & FeaturesThe modular architecture of the LX500TM systemenables the user to configure a measurement analyzerwith capabilities which meet their needs for variousdifferent kinds of applications and requirements.

Moreover the analyzer can be easily expanded, changed,and upgraded anytime in the future at substantiallylower cost than purchasing stand alone instruments.

The block diagrams shown here illustrate the variousfeature sets comprised in each model version.

Dual Frequency & Time Domain ModelThe Dual Domain model contains all the modules forboth Frequency and Time domain versions. Eithermodel version can be upgraded to the Dual version.

Frequency Domain ModelThe Frequency Domain version contains all of themodules needed for frequency domain measurements,but does not include the Time Domain modules.

There are a large number of modules involved with thefrequency domain version which support a large varietyof specialized functions and powerful capabilities.

The output section consists of dual low distortionOscillators and a White/Pink noise generator. Theoscillators can be combined to produced swept inter-modulation distortion testing, and also provide squarewave and gated waveforms.

An advanced 8-Pole programmable filter providestunable Bandpass, Bandstop, Lowpass, and Highpassfunctions for highly selective filtering.

An extensive assortment of Weighting and Bandwidthfixed filters are provided, along with multiple RMSdetectors, frequency counter, and phase meter.

Time Domain ModelThe Time Domain version contains all of the modulesneeded for time domain measurements, but does notinclude the Frequency Domain modules.

The analog output section and analog input sections arecommon and used in both model versions.

For time domain measurements stimulus is provided bya Digital Signal Generator module, while three DigitalSpectrum Analyzer modules capture the input signalssynchronously. Internal memory stores all sample data.

With sampled stimulus and data, all filtering or signalprocessing functions are performed mathematically inthe application software rather than hardware.

Dual Domain Block Diagram

Frequency Domain Block Diagram

Time Domain Block Diagram

Signal Generators and OutputsThe LX500™ generator system provides apowerful array of output capabilities andextensive precise signal generation features.

Dual outputs are provided with selectableimpedance, muting, and phase reverse. Bothbalanced and unbalanced signals are supportedutilizing a high performance electronicallybalanced circuit with high output common mode rejection (patented),along with coarse and fine output ranging attenuation.

Dual ultra low distortion oscillators produce sine, square, and synchronous gatedwaveforms. These waveforms can be combined for a variety of intermodulationdistortion tests. The oscillators utilize an advanced dual sampling level control circuitwith very fast stabilization and ultra high linearity (patent pending).

The Digital White Noise generator has a cycle time over 60 seconds yielding very highdiffusion and wide 250kHz bandwidth. The conversion to Pink Noise is handled by anadvanced filter design (patent pending) which yields accuracy 10 times higher thanprevious half-order standard filter topologies.

The 1st graph on the right shows the ideal pink noise filter response and a typicalstandard filter. Note that ripple remains throughout the half order slope region. The2nd graph shows the response of the LX500™ pink noise filter and is virtually identicalto the ideal response. The 3rd graph shows the actual error of the filters relative to theideal response, where the standard filter produces 0.5dB error, and the LX500™ pinknoise filter has amazingly low error on the order of 0.01dB.

The output section also features the Digital Signal Generator time domain modulewhich enables an unlimited variety of high resolution digital stimulus signals to begenerated, and also provides for the capability of External Signal Generation sourcesto be fed into the LX500™ output attentuation and driver system.

OSCILLATORLOGIC

CONTROL

OSCILLATORLOGIC

CONTROLGEN

SOURCE

EXTERNALGENERATOR

NOISESOURCE

OUTPUT-A

-70dBm/+26dBm40Ω/50Ω/150Ω/600Ω

CMRR 65dB

OSC-A

IM-1:1

IM-1:4

OSC-B

FILTER

EXT

NOISE

DIGITAL

LINEDRIVER

MUTEPHASE

IMPEDANCE

OUTPUT-B

-70dBm/+26dBm40Ω/50Ω/150Ω/600Ω

CMRR 65dB

LINEDRIVER

MUTEPHASE

IMPEDANCE


PINK NOISEFILTER

PROG FILTERBP,BS,LP,HP

OSC IM1:1/4:1

MULTI DAC GAIN/ATTEN

+10/0/-10/-20/-30


DACINTDACINT

DACINTDACINT



GENERATOR BLOCK DIAGRAM(C)opyright 2012 LinearX Systems Inc

BAL/UNBAL9VDC LVP

48V PHNTM

INPUT


CMRR 60dB



Multi Function Universal InputsThe LX500™ inputs have a low noise floor of -120dBm and a maximum input level capabilityof +40dBm, thus supporting a very wide input signal dynamic range of 160dB. Moreover theinputs provide the capability to power both LVP (Low Voltage Power) and P48V devices. Eachinput includes a high performance low distortion protection circuit to prevent signal overloadsfrom damaging input circuitry up to 250 Volts (patented).

The built-in Phantom 48V support enables the inputs to function as complete preamps for studio and music microphones withoutthe need and expense of an additional preamp/power supply. The LVP interface provides direct 9VDC power at up to 50mA forpowering any M30 or M50 microphone as well as the LP201 Accelerometer Preamp.

Note: The M31 microphone is not suitable for distortion measurements, rather the M50 series is recommended.

Rear ConnectionsDigital I/O Control is provided ona DB-25M connector. This can beused to control relays or read datain QC production lines.

Three External Monitor outputsare provided, an ExternalGenerator input (all on BNCconnectors), a USB interfaceType-B connector, and the12VDC power jack.

Programmable FilterThe LX500™ Frequency Domain version features a powerful advancednarrow band highly selective 8-Pole programmable filter. This filtercan be configured in several different modes to provide Bandpass,Bandstop, Lowpass, and Highpass transfer functions.

The Bandpass modes are shown here in the graph on the right. Thefilter is capable of producing 4 different response widths: 1 Octave, 1/3 Octave, 1/6 Octave, and 1/12 Octave. The passband region is veryflat and the allpole stopband regions attenuate out to infinity.

The Bandstop mode provides a precision elliptic notch response, witha typical attenuation over 110dB. Controlling the response of ellipticfilters is complex, and specialized architecture and tuning methodswere developed to produce a highly stable filter response.

The Bandpass and Bandstop modes are used in conjunction with thedual sinewave oscillators to provide many different measurementcapabilities for both harmonic and intermodulation distortion.

Room acoustic response profiles can also be measured using the PinkNoise Generator while sweeping in the Bandpass mode. The variousBandpass filter widths can be used to control desired detail.

The Lowpass and Highpass modes provide a means of adjustablebandwidth control. These can be useful for specialized testing such asrub/buzz to selectively filter for higher or lower harmonics.

2.00 Hz 5.00 10.0 20.0 50.0 100 200 500 1.00K 2.00K 5.00K 10.0K 20.0K 50.0K 100K 200K

+5.00

0.00

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-95.00

dB +5.00

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-95.00

dB BANDWIDTH FUNCTIONS

LP4-10K

LP4-20K

LP4-22.4K

LP4-30K LP4-80K

HP4-10

HP4-22.4

HP4-100 HP4-400

HP4-20

20.0 Hz 50.0 100 200 500 1.00K 2.00K 5.00K 10.0K 20.0K

+12.00

+9.00

+6.00

+3.00

0.00

-3.00

-6.00

-9.00

-12.00

-15.00

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dB+12.00

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dB WEIGHTING FUNCTIONS

ANSI-A

ANSI-B

ANSI-C

ANSI-D

ITU-468

ITU-ARM

ITU-041

C-MSG

F-CURVE

The Programmable Filter also has the ability to be placed in-line withthe output signal path. When using a noise generator source the filtercan provide bandwidth limited output noise. This is often useful foramplifier or transducer power capability testing.

Fixed Bandwidth and Weighting FiltersThe LX500™ provides an extensive array of powerful precision fixedfilters, both for bandwidth control and standardized weighting tests.Bandwidth filters have 4th order Butterworth-3dB transfer functions.

Five Lowpass bandwidth limiting filters are provide at:10kHz, 20kHz, 22.4kHz, 30kHz, 80kHz, or bypass.

Five Highpass bandwidth limiting filters are provide at:10Hz, 20Hz, 22.4Hz, 100Hz, 400Hz, or bypass.

Bandwidth limiting filters are often utilized in THD+N testing todefine the noise bandwidth or filter line related hum. They areessential for equipment noise measurements where the noisebandwidth must be precisely defined.

Nine different Weighting Filters are provided both for acoustical/vibration testing and communications testing comprising: ANSI-A, ANSI-B, ANSI-C, ANSI-D ITU-468, ITU-ARM, ITU-041, C-MSG, F-CURVE

These filters are generally used to perform standard noise measure-ments based on a prescribed filter response function.

Programmable Filter: Bandstop

500 Hz 1.0K 2.0K

+10.0

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0.0

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dB +10.0

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dB

4th Order Elliptic Notch Filter

MonteCarlo-Max

MonteCarlo-Min

Programmable Filter: Bandpass

100 Hz 200 500 1.00K 2.00K 5.00K 10.0K

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dB +5.0

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dB

1-Octave

1/3-Octave

1/6-Octave

1/12-Octave

500 Hz 1.0K 2.0K

+1.000

+0.500

0.000

-0.500

-1.000

-1.500

-2.000

-2.500

-3.000

-3.500

-4.000

dB+1.000

+0.500

0.000

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-4.000

dB

50.0 Hz 100 200 500 1.00K 2.00K 5.00K 10.0K 20.0K

+5.00

0.00

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dB +5.00

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dB Programmable Filter: Highpass/Lowpass

HP4-100Hz

LP4-10KHz

LP4-5KHz

LP4-2KHz

HP4-200Hz

HP4-500Hz

Signal Measurement in the Presence of High NoiseThere is always noise present during the measurement of any signal. The amount of noise may be small or large and is typicallydescribed as the SNR (Signal to Noise Ratio). Depending on the type of measurement method and the architecture of the analyzer,the impact of noise on both the quality and accuracy of the measurement can very widely. The issue of noise can play a critical rolein the design of an analyzer architecture and measurement method.

Typical electronic audio equipment has a very low noise floor, perhaps -100dBm. With a signal level of 0dBm the SNR is 100dB.However, acoustical tests are often conducted in an environment which can be relatively noisey with a background noise of perhaps60dBspl, while the signal level under test is 90dBspl. This is an SNR of only 30dB and presents a dramatically different situation.

The architecture of the LX500™ was specifically designed to handle the unique requirements of signal measurement in the presenceof high noise, or poor SNR conditions. This is very important for acoustic/vibration measurements where background noise levelscan be significantly higher as compared to electrical equipment measurements.

The ability to control noise is typically most easily handled in the frequency domain, since relatively low cost and high dynamicrange filters can be easily applied in hardware to define the measurement bandwidth, and to filter out unwanted portions of the signalspectrum. The LX500™ contains a number of specially designed frequency domain tools for exactly this purpose.

Most time domain sampled systems merely sample the incoming unfiltered wideband data and process the results. When thesignal contains substantial noise, the ability to separate the signal from noise and its effects becomes problematic. The DualDomain version of the LX500™ features a Digital Spectrum Analyzer module placed after the frequency domain filters, thusenabling post-filter sampling. This powerful architecture enables the incoming signal spectrum to be cleaned of noise and/orselectively filtered prior to time domain sampling. Very large dynamic range and/or high resolution measurements are possibleutilizing both the frequency and time domain features together in this manner.

Noise Considerations for Frequency Domain MeasurementsWhen high levels of noise are present in a frequency domain measurement there are a number of potential problems that shouldbe considered. These can be either Magnitude, Phase, or Distortion measurements.

Magnitude measurements are generally less sensitive to noise as measured by an RMS detector. The fixed Bandwidth Filters canbe used to define the measurement bandwidth, and are vitally important for equipment noise measurement, as are the WeightingFilters for standardized acoustic and communication system measurements. The Programmable Filter can be utilized in Bandpassmode for swept sinewave measurements providing wide or narrow frequency band selectivity and rejection of unwanted noise.

Phase measurements can be greatly affected by noise depending on the architecture and design of the phase meter itself. Thephase meter of the LX500™ was specifically designed to provide highly accurate results even under poor SNR conditions. Thecurves below demostrate an example. The top two graphs show a pair of signals with 90 degree offset and minimal noise, input tothe LX500™ Phase Meter and another phase meter. The Yellow data curve shows the resulting phase output, and both show -90°.

The bottom two graphs show the results when heavy noise is added producing an SNR of only 10dB. The LX500™ Phase Metershows almost no change in the resulting Yellow data curve. However, the other phase meter cannot produce any meaningful resultwith the Yellow data curve suffering convergence failure. It is completely unable to produce any stable phase data.

Distortion measurements come in many different types, and some are greatly affected by noise while others are not. One of themost common distortion tests is THD+N (Total Harmonic Distortion plus Noise). For this type of test the sinewave fundamentalis removed by a Bandstop filter and all the remaining spectral content is measured together. The THD+N test is commonly usedfor electrical equipment measurements where low background noise is common, but it is generally of much less value in acoustic/vibration applications where high background noise is often present.

Traditional distortion analyzers typically employ a very narrowBandstop filter which must be tuned with a PLL (Phase Locked Loop)in order to null/cancel the fundamental, shown here in the graph.

While this approach works very well for signals with low noise, it canbe problematic under high noise conditions where the PLL can encoun-ter problems with lock. This can result in very long sweep times due tothe inability of the PLL to settle/lock and TimeOut limits result.

The LX500™ utilizes a different approach where the fundamental isremoved by highly selective brute force precision elliptical filtering.There is no PLL lock or settling time issues involved, and noise levelsdo not affect the performance or speed of the test. The programmablefilter is merely moved to the correct frequency and the attenuation ofthe fundamental is performed instantly. Shown here in the graph.

The graphs also show the significant difference between the lower noiseenviroment of electrical device testing, and the higher noise environ-ment of acoustical testing. In THD+N the acoustical noise may entirelydominate the results masking the contribution of distortion components.

The LX500™ provides an additional means of distortion testing wherethe individual harmonics are measured directly as IHD (IndividualHarmonic Distortion). For this test the programmable filter is changedto Bandpass mode and centered over one of the harmonics to bemeasured. All other signal contributions are removed including thefundamental, other harmonics, and the background noise. Multiple andindividual IHD curves can be produced for 2nd, 3rd, 4th, harmonics etc.

IHD testing is especially useful for electroacoustic work where theamount of odd or even harmonic distortion is a valuable indicator ofsymmetry issues in the suspension or magnetic system of transducers.

The LX500™ provides yet another category of distortion testingcapabilities known as IMD (Intermodulation Distortion). The useful-ness of this test is described in the graph on the right.

There are two different Low/High frequency testing situations shown:a fundamental at 100Hz, and a fundamental at 10kHz. For each casethe resulting harmonic products are shown. In the case of the lowfrequency 100Hz test the resulting harmonics are 200Hz, 300Hz, etc.These would be clearly audible. However for the 10kHz test theharmonics are 20kHz, 30kHz, etc. which are inaudible.

The graph on the right shows a more meaningful measurement of highfrequency distortion by difference intermodulation. In this case a twintone stimulus signal of two sinewave frequencies is used at 9kHz and10kHz, the difference product being 1kHz. The programmable filter isused in Bandpass mode and positioned to capture the 1kHz distortion.This would be very audible and a better indicator of the distortionmechanisms of a high frequency device such as a tweeter or compres-sion driver. The LX500™ with independent dual oscillators and pro-grammable filter provides for swept difference and other intermodula-tion distortion capabilities across a wide range of frequency.

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FundamentalLow Frequency Harmonic Distortion

High Frequency Harmonic Distortion

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Twin-ToneFundamentalsBandpass Filter Response

Noise Considerations for Time Domain MeasurementsTime domain sampled systems comprise many different types of stimulus signals and types of testing and/or processing. Theeffect of noise on sampled signals depends on many factors including the type of test, stimulus, and spectral content of the noise.It is therefore difficult to make generalizations that will fit every circumstance and predict the accuracy of every possible result.This is a complicated subject where many users apply the tools and methods without understanding the issues and limitations.

The basis of sampled signal theory states that both the frequency and time domain are related and can be transformed betweenone and the other by the Fourier or Inverse Fourier Transform. This is based on the assumption of infinite bandwidth and infinitesampling resolution. However practical sampled systems do not have infinite bandwidth or infinite resolution, and are thereforeonly approximations known as discrete sampled systems, and they utilize the Fast Fourier Transform (FFT) for processing.

Early work on sampled system theory began with the assumption of perfectly clean signals free of noise with perfect linearity.These assumptions were simplistic, and recently more study has been given to the effects of noise and nonlinearity (distortion)and their effects on the results produced from time domain measurements. Acoustic/vibration applications generally involvemuch higher noise and much larger distortion, so these effects become extremely important for these types of applications.

Understanding the nature of a particular stimulus and its spectral content is a key factor. Stimulus types such as Impulse, MLS,and Chirp have often been used. However even these come in different flavors with much different spectral content. Forexample, the LX500™ provides both MLS-White Noise and MLS-Pink Noise as well as Linear Chirp and Log Chirp. The differ-ences between these reflect the desire to produce constant energy vs. linear frequency or log frequency. The effect of noise onthese types of stimulus signals will differ depending on the frequency range of interest and background noise content.

For example, the traditional MLS signal has a White noise energy distribution. For audio applications the energy content presentat 20Hz is 30dB lower than the energy content at 20kHz. If a large amount of background noise is concentrated at lower frequen-cies, it can severely affect the measurement accuracy in the lower frequency regions, where the test signal is weakest. In somecases both Magnitude and Phase data results are substantially altered.

Nonlinearity can also affect measurement accuracy. Different types of stimulus waveforms have different sensitivies to nonlinear-ity (distortion) of the signal. In some cases even a modest amount of nonlinearity introduced by the system under test willdamage the Magnitude and Phase results, as well as any Distortion measurements.

Distortion measurements are generally conducted by applying a pure sinewave stimulus, sampling the resulting signal, and thenmeasuring the resulting harmonics. However in the presence of high noise, the issue of dither becomes important. Dither occurswhen noise is added to a waveform and results in randomization of the distortion products. This can render distortion measure-ments unreliable, depending on the spectrum and amount of background noise present, and the sampling parameters.

Logarithmic vs. Linear Frequency ResolutionMother Nature in general and the Human Ear specifically operate onRatios of Change. A simple example is the music scale itself where anOctave is defined as a 2:1 frequency ratio of change, or the loudnessscale where the dB unit represents a logarithmic change in amplitude.

A frequency change from 100Hz to 200Hz is one octave, just as achange from 1kHz to 2kHz is also one octave. However in terms oflinear frequency the difference is 100Hz vs. 1000Hz respectively.

Frequency Domain measurements typically provide log frequencyresolution, while Time Domain measurements give linear frequencyresolution. The graphs shown here display 100 points of log and lineardata as plotted on a log frequency scale.

The 100 log data points are evenly spread across the entire log spectrum,while the 100 linear data points are concentrated at higher frequencies,with almost no data at lower frequencies. This is linear sampling.

In order to achive the same log spectral resolution across 3 decades offrequency, the Time Domain system will require about 330 times moredata points. Example: to provide the equivalent low frequency logresolution of 500 points, the Time Domain will require an acquistionlength of approximately 170,000 samples.

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Graphical Interface and Data DisplayThe LX500™ software provides a rich graphical user interface with a host of featuresgreatly enhancing the ease of operation and processing of measured data. All graphicsare designed on a generalized artboard layout, rather than screen specific fashion. Thescreen display is identical to the printed output. The user has full control over many ofthe design elements of the artwork including fonts, colors, and line styles.

Curve LibraryThe software features a powerful Curve Library which enables multiple curves to bestored, displayed, processed, and printed. Where most analyzer software limits you tooperating with a single curve, here hundreds of curves can be handled with ease.

Utilities and Processing ToolsThe software provides a rich set of utilities for manipulating data and graphics.Numerical data can be imported and exported from the program as simple ASCII textfiles. The graphic artwork can be exported as either vector or raster image files inmany different formats including: PDF, AI, EPS, WMF, EMF, BMP, TIF, PNG.

Macro ScriptingFor Production and QC testing applications the LX500™ software can be controlled byuser written Macro script programs. The Macro programming language allows formessages to be written to the screen to prompt operators, control test sweeps, runutilities, control printing of graphs, export data, and conduct Pass/Fail tests.

SoftwareThe LX500™ analyzer software is provided asa Windows® 32 bit application. It is possiblethat future versions may also include aWindows® 64 bit version, and possibly Linux32 bit and/or 64 bit versions.

Not only does it include all of the necessaryfeatures and capabilities to control theLX500™ analyzer, but it also includes asubstantial complement of data processing,post processing, specialized utilities, andextensive 2D & 3D graphics capabilities.

The software provides a large array ofpowerful computer based features ideal forboth R&D and production QC requirements.

Highlights• Curve Library for multiple curve displayoperations, processing, and printing

• Multiple Curve Copy/Paste through Win-dows Clipboard for easy data transfer

• Linear/Log Frequency Translation

• Linear, Quadratic, and Cubic dataInterpolation & Conversion routines

• Advanced Transducer Model Derivation

• Macro Script Programming for QC

• Macro Editor with Syntax Highlighting

• Curve Capture, distill actual numeric curvedata from any raster image

• Curve Editor, create or modify curves bygraphical editing utility

• Enhanced capabilities for Post Processingadvanced Math operations

• Enhanced capabilities for Polar Plotprocessing and resolution

• Multiple LT360™ Turntable Control

• Extensive Vector & Raster Graphics Export

• Data Import & Export routines

• 2D & 3D curve and waveform graphicsdisplay and printing

• OS support: Windows® 2000 or higher

Transducer Model DerivationThe LX500™ analyzer software contains a very powerful Utility for deriving transducer parameters from measured impedance data,and/or voltage and current data. This utility is furnished from the LEAP-5™ EnclosureShop™ software and is the most powerful andadvanced transducer parameter processor in the world.

The Transducer Model Derivation utility supports three different transducer models: STD, TSL, LTD. The standard model STD usesa minimal set of legacy parameters. The TSL model was created for LEAP-4™ , and the new advanced LTD model in LEAP-5™ addsnumerous parameters for highly accurate simulation across a large dynamic range. The transducer modeling capabilities containedin the LTD model are considerably more detailed and accurate then any previous transducer models.

The utility accepts from 1 to 9 different sets of impedance/voltage curves and processes these using an advanced nonlinear non-convex global optimization engine, both for the mechanical system and for the electrical system.

The LTD model produces nearly 60 pa-rameters that describe the transduceracross a wide range of drive levels andoperating conditions.

Impedance simulation curves areproduced for direct comparisonagainst the original measuredcurve data.

Various parameter curves arealso provided for inspectionof transducer characteristics.

The simpler TSL and STDmodels can be producedfrom a single measuredimpedance curve set.

Utilities and ProcessingThe LX500™ software provides a large array of powerful utilities and processing capabilities. A Curve Capture utility can distill numeri-cal curve data from raster images. These can be pictures from books, manuals, or scanned images of plotter output. The Curve Editor utilityallows you to graphically create your own curves, or edit the data of any curve in the library. Specialized computational and control utilitiesare also provided. Examples include: advanced derivation of loudspeaker parameters, polar plot data processing, and LT360 control.

Post ProcessingThe software also provides post processing mathematical functions, data processingfunctions, and other specialized import/export processing capabilities which can beapplied to measured data or imported data.

Smoothing, scaling, splicing, and other DSP operations give the user completecontrol over the measured data without the need for using external data processingprograms. The post processing features in the software enhance the user's ability toderive maximum use of the measured data.

One of the most important and powerful features is the ability to precisely manipu-late, control, and change curve data resolution and scale. Extensive facilities areprovided for Log/Linear conversion, resolution conversion, bandwidth control, andinterpolation/extrapolation of data.

LINEARX SYSTEMS INC9500 SW Tualatin-Sherwood RdTualatin, OR 97062-8586 USA

Tel: 503-612-9565 Fax: 503-612-9344www.linearx.com [email protected]

Visit our web site or contact the factory fora list of International Dealers.

All specifications subject to change without notice.© 2012 All Rights Reserved.Printed in the U.S.A.Revision 1.00AUG-01-2012

Computer Aided Engineering & Measurement Systems

Analog Signal Generator• Number of Outputs Dual Channel• Connector Dual XLR-3 Male• Signal Types Sine/Square, Dual Sine/Sqr, Sync Gated,

Precision White Noise, Pink Noise• Output Types 2-Ch Dual XLR Balanced:

Selectable Mute & Phase Reverse• Sine/Sqr Frequency Range 10Hz - 100kHz• Sine/Sqr Frequency Accuracy 0.25% or Better• Sine Wave Distortion <0.001%• Sine Wave Flatness <0.05dB• White/Pink Noise Flatness <0.05dB• White/Pink Noise Bandwidth 4Hz-250kHz• Attentuation Resolution 0.02dB or Better• Maximum Amplitude +25dBm (14Vrms)• Common Mode Rejection 70dB typ• Output Impedance 40, 50, 150, 600 Ohms

Input Channels• Number of Channels Triple Channel Input• Connector Triple XLR-3 Female• Input Functions Balanced, Unbalanced,

+48V Phantom Power,+9V/50mA Direct Power

• Input Impedance 100k Ohm Unbalanced,200k Ohm Balanced

• Input Noise 3.5nV/RtHz Unbal (-124dBm/20kHz),4.9nV/RtHz Bal (-121dBm/20kHz)

• Maximum Input 70Vrms (+40dBm)• Highpass Corner Bandwitdh 0.16Hz• Common Mode Rejection 60dB typ

Bandwidth Filters• Filter Order 4th Order, 24dB/Oct, 80dB/Decade• Filter Transfer Functions Butterworth 3dB Corners• Lowpass Corner Frequency None, 10kHz, 20kHz,

22.4kHz, 30kHz, 80kHz• Highpass Corner Frequency None, 10Hz, 20Hz,

22.4Hz, 100Hz, 400Hz

Weighting Filters• Acoustic Functions ANSI A, B, C, D• Communication Functions ITU-468, ITU-ARM, ITU-041,

F-Curve, C-Msg

Programmable Filter• Filter Order 8-Poles: 4th Order BP/BR,

4th Order LP/HP• Filter Functions Bandpass, Bandstop,

Lowpass, Highpass• Bandpass Filter Width 1 Octave, 1/3 Octave,

1/6 Octave, 1/12 Octave• Bandreject Attentuation 115dB typ• Frequency Range 10Hz-100kHz• Frequency Accuracy 0.25% or Better

Phase Meter• Reference Signal Generator Output• Selectable Source Inputs, Post Filter Meter Signal• Dynamic Range 60dB• Accuracy +/- 0.1 Degree, typ

Frequency Counter• Type Period, Auto Ranging• Update Rate 5 Readings / Second• Resolution 24 Bits• Accuracy 6 Digits, 0.01%

Digital Signal Generator• Word Size 24 Bit• Word Rate 216kHz, 108kHz, 54kHz, 27kHz• Waveform Sample Length 4,096 - 4,194,304• Sample Time Length 19mSec to 155 Seconds• Stimulus Type Sine, MLS-White, MLS-Pink,

Chirp Linear, Chirp Log, etc, User• Sample Memory Internal, 16MB PSRAM

Digital Spectrum Analyzers• Channels 4: 3-Inputs, Post Filter Meter• Synchronous Sampling Simultaneous on all Channels• Word Size 24 Bit• Word Rate 216kHz, 108kHz, 54kHz, 27kHz• Acquisition Sample Length 4,096 - 4,194,304• Acquisition Time Length 19mSec to 155 Seconds• Frequency Resolution 0.006 Hz• Sample Memory Internal, 16MB PSRAM

Monitor Interface• Connectors 4 - BNC• Functions Ext Gen Input, 3- Monitor Outs• Monitor Functions In-A or Gen-Output,

In-B or Pre-Filter,In-C or Post-Filter

• Ext Gen Input Impedance 100k Ohms• Impedance of Outputs 150 Ohms

Digital I/O Interface• Connector DB-25 Male• Digital Lines 16, Prog as Inputs or Outputs• Voltage Compatibility TTL (5V) or LVTTL (3.3V)• Supplied Power +3.3VDC (100mA Max)

System• Micro Controller Unit 96MHz/32b ARMTM Cortex-M3• PC Host Interface USB Full Speed 12MHz• OS / Software Windows® 2000 or higher• AC Supply Voltage Universal 85-265VAC / 50-60Hz• DC Supply Voltage +12VDC / ±20% / 2A max• Power Consumption 24 Watts Max• Dimension, Length 11 Inch, 280mm• Dimension, Width 6.6 Inch, 167mm• Dimension, Height 1.7 Inch, 43mm• Weight 3 lbs, 1.4 kg

Specifications

Documents

Big Features - Small Package! General System Features