Related Manuals for Rohde & Schwarz UPD
Summary of Contents for Rohde & Schwarz UPD
- Page 1 Loudspeaker measurements with Audio Analyzers UPD or UPL Application Note 1GA16_1L replaces 1GPAN16L Subject to change M. Schlechter 07.97 Products: Audio Analyzer UPD Audio Analyzer UPL...
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Page 2: Table Of Contents
Content 1 INTRODUCTION 2 PREPARATIONS 2.1 H ARDWARE AND OFTWARE EQUIREMENTS 2.2 S OFTWARE NSTALLATION 2.3 S TARTING THE PPLICATION OFTWARE 2.4 C ONFIGURING THE PPLICATION 2.4.1 S ETUP AND ONFIGURATION ILES 2.4.2 P RELIMINARY ONFIGURATION OF ETUP 2.5 C ONVERTING THE ETUP FOR OFTWARE... - Page 3 5.1.8 Q F ACTOR 5.1.9 E QUIVALENT OLUME 5.1.10 G 5.2 S OUND RESSURE EASUREMENTS 5.2.1 T ETUP 5.2.2 A DJUSTING THE UTPUT OWER 5.2.3 E NTRY OF ICROPHONE AND ARAMETERS 5.2.4 S ELECTING THE OUND RESSURE 5.2.5 S ENSITIVITY EASUREMENT AND ADIATION NGLE...
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Page 4: Introduction
This application contains a BASIC program permitting automatic measurements of loudspeaker parameters with the aid of the features described above. The program can be run on UPD with UPD-K1 and on UPL with UPL-B10. The application software supports the following measurements or measurement sequences: •... -
Page 5: Software Installation
The application software is loaded and started under the universal sequence controller. So the device software has to be started first (either by switching the instrument on or by calling up the UPD/UPL at DOS level) and then the universal sequence controller is selected with key F3 (external keyboard). -
Page 6: Configuring Thea
2 2 .4 .4 Configuring the Application Configuring the Application 2.4.1 Setup and Configuration Files The application software uses two different sources for device setting: SPEAKER.CFG: Configuration file holding all user entries (see section 3.4, Entry of Parameters) or default values on initial call-up. When the application is started, this file is loaded; when the application is left using the EXIT softkey (see section 7, Terminating the Application) the file is stored with updated values so that the entries made by the user during the last run are reinstated on starting the application again. - Page 7 The application software is tailored to the audio range, ie to the 25-kHz generator and a 22-kHz analyzer. In the UPD instruments for higher frequencies may also be selected but in this case the following aspects have to be considered: •...
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Page 8: Operating Concept
Each level may have up to eight active softkeys; unassigned softkeys are blank. Same as in the UPD/UPL device software, function keys F5 to F12 correspond to softkeys #1 to #8. -
Page 9: Entry Of Parameters
• Softkey #2 (F6): o <--> O changes from partial to full graphics display and vice versa. • Softkey #3 (F7): GOTO UPD changes temporarily to the UPD operating software (see section 7.1, Change of Task Application/User Interface) • Softkey #4 (F8): HARDCOPY outputs the screen content to a printer or file (see section 7.2.2, Printout during Application Run) 1GA16_1L.DOC... -
Page 10: Measurement Modes
Note: The highest resolution (2.9296875 Hz at 8 k zoom FFT) makes only sense in the UPL, as the UPD is not able to track a resolution of < 5.859375 Hz because of its higher internal generator clock rate. -
Page 11: Frequency Sweep
• The frequency resolution can be improved without any restrictions by reducing the frequency range; with FFT the smallest step is fixed to 5.86 Hz (UPD) or 2.93 Hz (UPL). • The generator setting time for each sweep point is very short while a time-consuming noise-signal generation is required with FFT noise. -
Page 12: Fft Noise
• "Window RECTANGULAR" switches off the window function. • "Zooming ON" (with zoom factor 2) is only possible in the UPL, as the UPD generator is not able to set frequency resolutions below 5.8584 Hz. 1GA16_1L.DOC ROHDE & SCHWARZ... -
Page 13: Swept Burstm
4 4 .4 .4 Swept Burst Measurement Swept Burst Measurement In this mode, not a continuous but a burst sinewave signal is swept, ie varied in frequency. A whole number of periods is measured, the burst duration is one period longer than the measurement time. This mode is used for measuring the transmission range as with this measurement reflections in the room can be eliminated by simple means. - Page 14 If the DUT is within the specified tolerances (limits), "DUT passed" is displayed. If at least one measured value is out of tolerance, "DUT failed" is displayed. If a macro is used, the macro is stopped and the instrument waits for a keystroke. At the end of the measurement, the reference curve is stored by pressing the STO REF softkey and entering a file name.
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Page 15: Measurements
Q t , resonance frequency f r and equivalent volume V eq . Equations used in this Application Note are in line with DIN IEC 268, part 5. Since UPD and UPL comprise a DC generator and a DC measurement function, the DC impedance can be measured without any additional equipment being required. -
Page 16: Special Notes On
The open-circuit generator voltage V q being known, the following voltage ratio is obtained: / Z+R = U Because of the complex impedance, the equation cannot be solved for Z, but the generator may be used as a current source for Z << R so that the following applies: Z = U For impedances in loudspeakers, the condition Z <<... -
Page 17: Dc Impedance
5.1.3 DC Impedance The DC impedance R DC is required for calculating the quality (see section 5.1.8, Q Factor). The measurement is carried out with the DC function. The offset which can be set with almost all generator signals is used as the DC signal; the AC signal level is set to 0. - Page 18 FIG 7: Impedance characteristic and evaluation of a multi-path loudspeaker (Trace B shows the impedance characteristic referenced to a "golden unit") 5.1.5 Resonance Frequency and Resonance Impedance The resonance impedance Z r is the first main maximum in the impedance curve at the resonance frequency f r .
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Page 19: Tuning Frequency
5.1.7 Tuning Frequency The tuning frequency is the frequency at which the impedance curve shows the first minimum after the resonance frequency at increasing frequencies. It can be read directly from the impedance curve with the aid of the graphics cursor. In the program it is obtained by scrolling up through the impedance data array, starting at f r ;... -
Page 20: Equivalent Volume
5.1.9 Equivalent Volume The equivalent volume V eq of a loudspeaker array defines the air volume, the compliance of which is equal to that of the loudspeaker array. First the impedance measurement is carried out with the loudspeaker array open. The loudspeaker is then accommodated in a small, rigid housing without any further openings and additional insulation and a new measurement is started with the V softkey (F11, level 4). -
Page 21: Test Setup
The input of the power amplifier is connected to the XLR output (channel 1) of the UPD/UPL generator, the power amplifier output in parallel to the DUT and to the XLR input (channel 1) of the UPD/UPL analyzer. This allows the output power of the power amplifier to be determined. For measuring the sound- pressure characteristic the standard microphone is connected to the XLR input (channel 2) of the UPD/UPL analyzer (if required via the microphone amplifier). - Page 22 In this case the UPD generator outputs the constant voltage selected under VOLTAGE (F6, level 3). The amplifier output power is constantly measured by the UPD analyzer and displayed in a bargraph (trace B) and as a numerical value (function window of channel 1).
- Page 23 (not recommended in the FFT noise mode because of the noise generation time) or • after the first main measurement by changing to the UPD display panel (see section 7.1, Change of Task Application/User Interface) and manual switch-off (OFF) of trace B.
- Page 24 5.2.4 Selecting the Sound Pressure Unit With the aid of the UNITS softkey (F9, level 3) the unit of the sound pressure displayed as a measured value or curve can be selected. This selection also determines the reference value and the reference mode (lin.
- Page 25 The measured sensitivity may be used as a reference for measuring the frequency response or the radiation angle. This is done by pressing the STO SENS softkey (F10). This measurement can also be used for determining the radiation angle. In this case the standard microphone (at a constant distance from the loudspeaker) has to be moved away horizontally from the reference axis in the course of the long-term level measurement until the sound pressure level falls by 10 dB.
- Page 26 Since the burst sweep is not directly available as a measurement function in the UPD or UPL, its function will be briefly described below: Burst sinewave signals with a length of integral periods of the sweep frequency are used as measurement signals (to avoid DC components).
- Page 27 The sinewave sweep should be used whenever no significant echoes are expected, eg in the near field or in anechoic chambers. Near-field measurements in the combined near/far-field measurement are always performed with a sinewave sweep. FIG 12: Measurement of transmission range using a sinewave sweep in an anechoic chamber With the START softkey a level sweep or an FFT is started;...
- Page 28 The frequency range and the number of sweep points for the near field are determined under CFG NEAR (F8). If an additional far-field measurement is not performed, it can be switched off here (F6, the ON or OFF state is indicated in the softkey). The transition frequency between the near and the far field (TRANSFRQ, F9) can be preset as a numerical value.
- Page 29 In a setup without power amplifier, the generator outputs are connected in parallel to the loudspeaker and to the XLR input of the UPD/UPL analyzer (channel 1). The standard microphone is connected to the XLR input (channel 2) of the UPD analyzer (if required via a microphone amplifier).
- Page 30 or after the start of the signal travel time − < Same as with sound pressure measurements, the microphone distance is entered with the DISTANCE softkey (F8, level 4) in the MICROPHN me nu. The distance entered in this menu is used as a default value (see DISTANCE in section 5.2.3, Entry of Microphone Parameters).
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Page 31: Polarity
5.4.1 Measurement Function POLARITY for Electrical Systems UPD and UPL provide a measurement function and a corresponding generator function for measuring the polarity of electrical systems (cables, crossover units). In this case a (DC-loaded) sine 2 pulse is generated and the measured polarity is displayed as "+ 1 Pol"... - Page 32 5.4.2 Polarity Check by Comparison to Reference Phase Measurement This procedure is based on the fact that incorrect polarity of a system causes a phase shift of 180°. For the check a correctly poled reference system is set up at an exactly defined distance from the standard microphone and the phase between generator signal and output of the standard microphone (or microphone amplifier) is measured.
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Page 33: Distortion
5 5 .5 .5 Distortion Distortion The UPD and UPL device software offers several functions for determining the distortion of a signal - and thus also of the sound pressure produced by a loudspeaker. The following functions are available for example: •... - Page 34 Except for ZOOM FFT, measurements can be carried out as single measurements (SINGLE, started with F11) or in the form of a sweep (SWEEP, F12). After pressing the SNGL FRQ softkey (F10), the frequency for a single measurement is entered under FREQ RNG (F7) the frequency range for the sweep. % or dB can be selected under UNIT (F9).
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Page 35: Macro Operation
6 6 Combining Several Measurements Combining Several Measurements In many cases it may be required to start operating steps or whole test sequences by a single keystroke. If a certain test sequence has been tried out and is to be frequently used, it should not be necessary to set each measurement step manually. -
Page 36: Running A Macro
6.1.2 Running a Macro A macro is started by one of the START softkeys in the macro menu. • VIEW RUN starts the macro and waits for a (predefined or explicit) macro name to be entered. The sequence is then performed as in manual operation using softkeys. •... - Page 37 Note: Upon installation of the SPEAKER software the installation program checks whether the macros SPEAKER0.MAC to SPEAKER6.MAC do already exist. If this is the case, the macros are not re- installed to prevent user-defined macros to be overwritten. If a re-installation is desired, the macros in the SPEAKER directory must first be cleared.
- Page 38 1GA16_1L.DOC ROHDE & SCHWARZ...
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Page 39: Printout
7 7 .2 .2 Printout Printout To print hardcopies, a printer has to be connected to the UPD/UPL and configured. It is important that a suitable printer driver is selected. Respective information is given in the UPD and UPL operating manuals. -
Page 40: Printout At User
7.2.1 Printout at User Interface The application has to be quit by means of the GOTO UPD softkey (F7), (see section 7.1, Change of Task Application/User Interface). Same as with normal instrument operation, printout is triggered with the HCOPY hardkey. Any comment can be entered. - Page 41 8 8 Terminating the Application Terminating the Application Normally, the application software is terminated with the EXIT softkey (F5) at the top softkey level (see section 3, Operation Concept). Since at lower softkey levels the left-most softkey (F5) is assigned the BACK function, the application can be terminated from any softkey level by pressing the F5 softkey several times.
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