Real Time Analyser Nor-840
Features:
Dual channel measurements in true octave and third octave bands 0.1Hz-20kHz frequency range in both channels in dual channel operation True A- and Lin spectral weighting networks in both channels Easy-to-use single-level menus and direct key control Large colour VGA display Microphone, line and charge inputs Powered from 12Vdc 80dB dynamic range Internal memory for up to 32000 spectra Internal 3.5" MS-DOS compatible floppy disk drive IEEE-488, Centronics and RS-232C interfaces Multispectrum measurements (level vs. time) Internal signal generator (optional) Internal reverberation time calculations (optional) Sound intensity measurement capabilities (optional) True 1/12 and 1/24 octave filters (optional) 800 lines dual channel FFT (optional) Maximum Length Sequence (MLS) for measurements of level differences and reverberation time calculations (optional) Handy unit for field use
Introduction
The dual channel real time analyser Nor-840.	The Norsonic dual-channel Real-Time Analyser Nor-840 has been developed to meet the requirements of the most experienced acousticians. To achieve this, our designers have used the latest available technology in order to provide an easy-to-use analyser. The battery operated Nor-840, has a bright, back-lit 10" colour LCD screen. The operator accesses all set-ups using dedicated push-keys to open logical menus. All setups are therefore selected using only single-level menus -- there is no need to navigate through multi-level menus!
Easy-to-Use Menus
The operation of the Nor-840 is optimised for quick and easy use. To obtain this, all operations required during the measurement sequence are made by direct use of dedicated keys. All set-up selections are made by use of single-level menus. Menu example. In the menus you may select the appropriate field by pushing the arrow-keys, and then selecting the required setting using the DIAL on the front panel. Alternatively, the PREVious and NEXT keys may be used instead of the DIAL. To speed-up the use for an experienced user, all selections may also be made by a numerical key sequence. For the non-experienced user, a HELP description is available for any field in any menu.
Signal Inputs and Outputs
The signals to be analysed use different input sockets for each channel. The inputs sockets are on the left side of the analyser to prevent dirt entering the sockets when the analyser is used in a rough environment, and in order to prevent cables masking the front panel. Fig. 1 The panel of sockets for connecting transducers to the analyser. Microphone preamplifier input. The 7-pin LEMO-socket supplies 0,28 or 200 V microphone polarisation voltage as well as 120V supply voltage, and may also supply 12V heating for the preamplifier. It is compatible with the Norsonic Preamplifier type 1201, but other sockets, B&K type etc. can by supplied on request. The polarisation voltage is selectable using a three-step miniature-switch.The heating voltage is selected by a two-step miniature-switch. Direct input. Using standard BNC sockets, the analyser may measure any signal in the range 1 µV to 30 V. Charge input. Accelerometers (for vibration analysis) may be connected to the analyser via standardised TNC sockets. Intensity input. Sound intensity probes may be connected to the 18-pin LEMO socket. This socket also includes an RS-422 digital serial interface to be used with the Nor-840 Intensity probe Nor-240 and the remote control unit Nor-245. Signal output. The attenuated wide-band signal from any input may be fed to external instruments via the BNC output socket.
Input Selection
The signal input is selected by pressing the INPUT key on the front panel. In the menu, the operator selects between the different input sockets. There is also a choice of different analogue filters. All inputs have an additional 3-order Butterworth High-Pass filter with -1.0 dB points selectable to 0.63Hz or 20 Hz. In addition, a 2 kHz Low-Pass filter (3-order Butterworth) may be selected for the Charge inputs. Fig. 2 Signal input selection is made in the Input Selection menu which is activated by depressing the INPUT key. Measurement Gain Selection The measurement gain -- corresponding to the full scale setting -- is set by the GAIN 1 or GAIN 2 keys for the respective channel. The gain may be adjusted in 5 dB steps over the range +50 dB to -20 dB corresponding to a measurement range of 1 µV to 30 V with the 80 dB dynamic range. There is also an autorange feature for each channel. Fig. 3 The input amplifier gain setting which controls the full scale setting provides the setting value in dB as well as in absolute units.
Calibration
Calibration is done by means of the Calibration menu which is produced by depressing the CAL key. In the corresponding menu, the calibration of both channels may be selected between direct sensitivity and voltage sensitivity adjustment, or autocalibration by entering the calibration level and frequency. Fig. 4 The calibration menu. Note that you can set up the analyser for autocalibration (by keying in the calibrator's output level). You may also choose between dB and absolute (engineering) units. Finally the 0dB level may be set to 5×10-8, 1×10-6 or the well known 2×10-5 (20µPa) sound pressure reference level.
Analogue to Digital Conversion
The analogue section of the Nor-840 is located inside a separate enclosure inside the analyser. This design ensures excellent internal noise specifications. Similarly, the analogue and digital parts of the analyser have separate grounding systems. Following the analogue input sections with their gain, filtering and sensitivity adjustments, the Nor-840 has 16 bit analogue to digital converters. The ADC includes a 22 kHz 12th-order Chebychev anti-aliasing filter in each channel.
Digital Signal Processing
The Digital Signal Processor (DSP) used in the Nor-840 is a 32-bit version. In order to provide 20 kHz digital 1/3-octave filtering as well as both true A- and Linear-weighting networks in each channel simultaneously, there are three DSPs in the instrument. This powerful design ensures that the Nor- 840 measures all frequency bands as well as the true networks to the latest, most stringent Standards available (see the Specifications for details). The DSPs perform level or intensity measurements in either true 1/1- or true 1/3-octave filterbands. Optionally, the operator may select true 1/12- or true 1/24-octave filters. These narrowband filters have an upper limit imposed on their real-time performance depending on the selected filterband, averaging time, etc. If the instrument is updated to include the FFT option, the calculations are performed by the same powerful array of DSPs.
Measurement Setup
Before a measurement is started,your normally use the menus to setup the analyser as required. Alternatively, you may simply load a setup-file stored on the floppy, thereby getting the analyser ready in a few seconds. The analyser automatically enters the Analyser-Mode when turned on. Alternatively, the user may select the optional postprocessing internal PC by pressing the DOS key. Fig. 5 The Measurement Setup menu provides detailed control of the parameters to be used in measurement. Note the ability to do serial measurements in a real time analyser! From time to time you need to collect all the available output power of a building acoustics noise source into just a single frequency band to create a signal loud enough to penetrate the background noise level. Assuming the Nor-840 is in the Analyser-Mode, your next choice will be between digital filtering or the optional FFT calculation, followed by selection of normal level measurements or optional intensity measurements. Finally, use of the M.SETUP key displays the menu for selection measurement parameters such as bandwidth, time-constant, measurement period lengths, etc. The measurement period length is selectable in 1 msec steps from 4 msec up to 100 hours.
Measured Functions
For single level measurements, the following functions are measured for each individual frequencyband or spectral weighting network: SPL based on selected time-constant Lmin based on selected time-constant and period length Lmax based on selected time-constant and period length Leq over the period length SEL based on period length In addition, the true A- and Lin-networks measure the true Peak values.
Trigger Features
The measurement is started by pressing the START key. As long as the measurement is running, a red LED will be illuminated on the front panel. Alternatively, you may specify that the measurement should start in accordance with a certain set of trigger conditions. The trigger condition is set in the Trigger-Menu. For simplicity, this menu is activated by pressing the 2nd and START keys. Fig. 6 The Trigger Setup menu provides detailed control of the trigger conditions to be fullfilled before the measurement actually starts. Available trigger conditions are: Manual (unconditional) Level above a certain threshold in a certain frequency band Level below a certain threshold in a certain frequency band External Level exceeds a certain threshold in a certain frequency band Level drops below a certain threshold in a certain frequency band Clock Noise On Noise off The term frequency band should here be interpreted as to also include available spectral weighting networks (but not any user-defined spectral weighting networks)
Multispectrum Measurements
If you need to measure several periods in sequence (level vs. time at equidistant moments in time), this can easily be achieved in the Multispectrum Mode. Fig. 7 Multispectrum measurements log the time profile by making measurements at predefined, equidistant moments in time. In this way you will be able to later follow a certain frequency band or spectral weighting network as a function of time or you may inspect the spectrum at a given moment in time. Pressing the MULTI key (instead of the SINGLE key), the Nor-840 will display the setup menu for multispectrum measurement by a simple press on the M.SETUP key. This menu differs from the previous setup-menu with settings for the number of periods to be measured, and the possibility to select a limited number of pretrigger periods. You may also limit the number of functions to be measured in order to maximise the capacity of the available memory. Typically, the Nor-840 may measure more than 10.000 spectra for a single function in the multispectrum mode. Fig. 8 The Multispectrum Mode Measurement Setup menu provides detailed control of all relevant measurement parameters, including time resolution and which functions (called values in the menu) to measure.
Measurement Title
Each measurement may be described by a title which automatically will follow the measured data when transferred to other registers or mass-memories. The title is keyed-in using the ALPHA setting on the front panel, or by use of a standard PC-keyboard attached to the analyser. The maximum length of the title is 400 characters divided into 10 lines containing 40 characters each. The first 20 characters are displayed when viewing the measured results in a window with added information.
Display
The Nor-840 display is a 10.4" backlit LCD colour screen with excellent properties regarding view-angle and readability. The Nor-840 also includes a VGA colour output that can be connected to any VGA colour monitor. Unlike many laptop PCs, the VGA monitor and the internal LCD screen function simultaneously!
Viewing the Results
The Nor-840 can display different measurements at the same time, or the same measurement in different views. This is achieved by a very flexible display setup with individual setup-menus for the upper and lower result windows. Fig. 9 For presentation of the measured results you have four different display modes (here shown using frequency domain graphs). Upper left shows the default setting: Dual display with setup information. Upper right shows the Single display. Lower left shows the Single display with condensed setup information while the lower right shows the dual display without setup information. Any of the graphs (upper, lower or both) can be level vs. frequency, levels vs. time or either as tabulated values. In addition the two graps may be set to show the contents of different registers, so that while one shows the current measurement, the other may show a stored one. The display is controlled by three direct access buttons: The TYPE key toggles from dual window screen with added information, through single window display, with or without setup information, and back to dual window screen with or without setup information. The NUM key toggles between numerical or graphical screen both for frequency spectrum and level vs. time screens. The Lf/Lt key toggles between a normal frequency spectrum (Level vs. frequency) and a screen showing the measured levels versus the number of periods measured (Level vs. time).
Display Setup
The D.SETUP key enters the display set-up menu. Depending on the selected active window, the menu for the upper or lower window is displayed. Fig. 10 The Display Setup menu gives you full control of the displayed functions. Note that there is one such menu for each of the two graphs (the upper and the lower). Also note that the upper and lower graph may show any available function. Unlike many other analysers, the Nor-840 does not insist on having ch.1 at the top and ch. 2 at the bottom. You have full freedom! The lower line in the menu lets you copy the display setup to the other Display Setup menu, so that you don't have to start from scratch. In the Display Setup menu, you may specify different settings that control the pictures seen in the upper or lower window: Channel selection. Selects a view of channel 1 and/or channel 2, or the difference between the two channels, or the difference between one channel and a selected reference spectrum. Y-unit. The units along the y-axis may be set to dB or engineering units. Time Cursor. The time cursor used with the multispectra measurements is set to number of periods, relative time referred to trigger, or absolute time. Displayed curves. Up to three of the measured functionss for each frequency band (Leq, Lmin, Lmax, SEL, and Peak) may be viewed as graphical curves in the same window. Displayed (spectral weighting) networks. Up to 4 spectral weighting networks may be viewed together with the frequency bands. The 4 networks may be selected from: True A- or Lin-network, Summed A-, B-, C-, or Lin-network, User-specified summed W1, W2, W3 or W4-network. Numerical table. The contents of the 6 columns in the numerical table may be selected from those parameters available for the specified measuring mode. For level mode measurements this means Leq, Lmin, Lmax, SPL, SEL and Peak, as well as the N-Leq counter for averaged measurements. The difference between "true" and "summed" spectral weighting networks lies in the following: True spectral weighting networks are real filters. Summed spectral weighting networks have their values calculated from a weighted sum of all the frequency bands used. This means that summed A (based on e.g. third-octaves) and true A may yield different results if the summed A frequency range is different (typically smaller) from that of the true filter.
DIAL Selections
For speedy selections in menus and on the screen, the Nor-840 is equipped with a dial. This dial functions in parallel with the PREVious / NEXT keys and is coupled to that of the CURSOR, Y-MAX, Y-RANGE, X-MIN or X-RANGE keys currently selected. In addition, if a menu is displayed, the dial alters the setting of the preselected menu parameter in predefined steps.
Cursor Control
As the upper and lower windows have their own individual setup, they also have dedicated cursors. The cursor is controlled by the dial (or the PREVious / NEXT keys) in order to step from one frequency band to another. A relative cursor or harmonic cursor may be also be selected in lieu of the normal cursor. For obvious reasons the harmonic cursor applies to FFT only. When both windows display the same results graphically and numerically, the cursors may be aligned to the same frequency bands. Even if the two displays show level vs. time and spectrum respectively!
User-defined Spectral Weighting Networks
Some measurement tasks require results weighted according to pre-defined spectral weighting networks. Although the Nor-840 already includes the familiar A-, B-, C- and Lin- spectral weighting networks, it also permits you to predefine other spectral weighting network functions. Such predefined spectral weighting network functions are designated W1-W4, and are selectable in the Display Setup Menu. You may have a large number of spectral weighting network functions stored in the mass-memory, and recall different sets of networks from one measurement task to the other. One example could be to have the range of spectral weighting network functions for whole-body and hand-arm vibration measurements stored as a set and recall this set of functions when making human vibration measurements. Spectral weighting networks may be generated directly from a measurement, but you may also key them in by hand! These customised spectral weighting curves may be applied in three ways: as reference curves as a weighting function applied to the displayed spectrum as a bargraph showing the combined level of the measured frequency bands Fig. 11 The three ways of applying the user-defined spectral weighting functions: 1 as reference curve; 2 as a weighting function for the spectrum and 3 as a bargraph showing the combined level of the frequency bands used in the measurement.

Hardcopies

Documentation of the results is an important part of any measurement. Hence, the Nor-840 allows its user to have a selection of numerical and graphical documentation. A press on the PRINT key will immediately generate a numerical listing of the results, while the PLOT key generates a graphical screen-dump plot. Parameters to be printed are selected by use of the numerical table settings in the Display Setup Menu.

Internal Memory Capacity

The memory structure inside the Nor-840 has been designed with maximum flexibility in mind. The internal memory has the capacity of storing a multispectrum measurement consisting of up to 10.000 spectra. A multispectrum measurement consists of several spectra logged at equidistant moments in time. Illustration of this. The exact number of multispectrum measurements will depend on the ratio of dual channel/single channel measurements, the number of functions logged in each measurement, the bandwidth (i.e. the number of employed octave/third octave bands) used etc.

Transfer Between Registers

The data acquired (i.e. the measured results) are generally transferred and copied between the different registers and mass-memories by use of the COPY, MOVE or COMBine keys, although there are some practical restrictions. The LAST register contains the results from the latest measurement. Data can only enter this register from the transducer/line input sockets. The AVRG register contains data transferred by use of the COPY or MOVE keys from any other register. These data are automatically averaged with those data already residing in the AVRG register. Hence, this is the register used for making averages of different measurements. The COPY key generates a copy of the data to be transferred, while the MOVE key generates a transfer while it at the same time clears the register where the data resided before the transfer. When the COMB key is used to generate the transfer, the AVRG register automatically combines two spectra with different frequency ranges. Hence, intensity measurements made by probes with limited frequency ranges can easily be added. The AUX register automatically receives the data loaded from the 3.5" floppy-drive, or from the hard disk included in the post-processing PC option. Finally, the USER register is used for making changes or calculations on previously measured data. In this register the user may add or subtract spectra, and display in any suitable format.

Mass-Memory

Frequency analysis, and particularly multispectral analysis, easily produces large amounts of data. Hence, a practical analyser needs a large memory to store the acquired data for later use. Norsonic introduced the internal floppy-drive concept in the Nor-830 back in the eighties. A sensation at the time! Since such such things no longer are a sensation, but a necessity, the Nor-840 comes with an optional 2.1 Gbyte hard disk (as per June 2000) as well as a floppy disk drive. The exact size of the hard disk will depend on the time of delivery. On demand, the analyser stores the measurement files with a pre-defined name. For repeated measurement, this feature enables you to have all the measurement files stored sequentially.

User Defined Setups

In addition to all results stored in the mass-memory, the Nor-840 will store complete measurement setups. This way you will be able to set the analyser to any predefined set of settings by selecting the proper measurement setup file. By inserting a predefined floppy in the 3.5" disk drive before turning the analyser on, the Nor- 840 will automatically be initialised using this setup. This means that you may tailor the instrument to fit your current needs without having to run through a complete setup procedure manually.

Optional Post-processing PC

Today small and handy laptop and notebook PCs are available everywhere. So, why include a PC inside a measuring instrument? By having the Nor-840 equipped with the post-processing PC, there is no need for extra boxes and no need for sometimes complicated cables between the PC and the analyser. Simply enter PC mode by a push of a button, hook up a PC keyboard to the Nor-840 (if desired), and run your programs using data directly from the internal floppy-drive or hard disk.

Sound Intensity

Sound intensity measurements require the optional intensity extension. Intensity measurements may also be made as multispectra when required. Both direct reading pu-probes as well as pressure-gradient pp-probes may be used. Fig. 12: Intensity probe examples: To the left, the p-p probe Nor-240 and to the right, the (now discontinued) p-u probe Nor-216. The advanced display features enables you to view the intensity results in any suitable format, and by use of the optional internal PC different field indicators are calculated within seconds. We offer a special software program for this - the Nor-9614. Fig. 13: Example of the Nor-840 sound intensity display, her set up to display the instantaneous sound intensity level (upper graph) and the equivalent sound intensity level (lower graph).

Internal Signal Generator

A multitude of acoustic and vibration measurements require a sound source with a specific signal, such as octave band pink noise for sound reduction testing of building elements. The Nor-840 can be equipped with an internal signal generator that produces random or pseudo-random white, pink or bandpass filtered noise to be fed directly to a power amplifier through the BNC socket on the right side of the instrument. When equipped with the optional MLS extension, the signal generator is further enhanced.

Reverberation Time

Based on a multispectrum measurement used in combination with the internal signal generator (or an external impulse generator), the Nor-840 can measure reverberation time. The calculated reverberation times are stored as normal data, and may later be used by the post-processing PC to calculate room acoustical or sound insulation parameters. In order to simplify the instrument set-up for reverberation time measurement, this function is provided with a special front panel key to access the function directly. As an option the Nor-840 may be equipped with Maximum Length Sequence, a measurement mode which opens up for level difference and reverberation time measurements in areas with very high background noise level.

Fast Fourier Transform (FFT)

The optional FFT extension turn the Nor-840 into a fully operating dual channel FFT analyser. Calibration settings are shared with the real time (fractional octave) analyser part. All calibration takes place in the real time analyser mode to preserve consistency between the two modes. Fig. 14: Example of the Nor-840 FFT display The 801 line FFT is equiiped with rectangular, Hanning, exponential and a user defined cosine-tapered rectangular window functions. The upper frequency range can be varied in 6 steps from 25000 Hz down to 195.3125 Hz providing a frequency resolution of from 31.2500Hz down to 0.2441Hz. The fine frequency resoloution is available throughout the entire frequency range by means of the zoom function. All calculations of functions are based on measurements of the two autospectra and the cross spectrum. The following functions are available: Autospectrum Cross spectrum Autocorrelation Crosscorelation Coherence Frequency response H1 Frequency response H2 Weighted time Weighting window All spectra can be scaled in: PWR RMS PSD ESD The cursor functions include a reference cursor and a harmonic cursor to identify harmonic contents in the measured signal. For vibration measurement purposes an on-screen integration feature is available. Analysers equipped with the FFT mode has an extended signal generator offering multi-sine in addition the standard features. The idea behind this is to provide a signal whose frequency components coincide with the lines of the FFT spectrum. By doing this there will be no signal energy outside these lines and the signal will have a perodicity equal to the time buffer length. Hence rectangular weighting can be applied without introducing discontinuities at the extremes. The phase of each of these sinusoids has been adjusted to give a total crest factor much lower than that of conventional noise. The crest factor is approximately 1.3 (as opposed to a single sinusoid which has 1.4142).

Digital Interfaces

On the right side of the instrument, are all the digital interface sockets. The basic version of the Nor-840 includes the following digital interface possibilities: IEEE-488 parallel interface for both remote control and data readouts. RS-232C serial interface with selectable baudrate. The interface is alternatively used for the same purposes as the IEEE-488 interface. CENTRONICS parallel interface for direct access to a hardcopy printer. There is also a standard VGA colour output socket for connection to a standard VGA monitor. Unlike many laptop PCs, the VGA monitor and the internal LCD screen function simultaneously! The BNC socket is the output from the signal generator. This socket is included in all Nor-840 units even if the signal generator option is not installed.

Battery Operation

The Nor-840 can run directly off a 12 Vdc source. Hence, all units are delivered with a 230 Vac (or 115 Vac) to 12 Vdc external Mains Adaptor Nor-329A. For field use, Norsonic offers different battery packages, as the battery capacity is related to the weight of the battery. The standard solution is the Battery Case type Nor-330A which contains a 5 Ah rechargeable battery and a quick-charger. This combination gives more than 2.5 hours of continuous operation for the Nor-840 with 2 hours recharging time. Weight 3.2 kg. A LED indicator on the battery box indicates the remaining battery capacity. A 10Ah version Nor-332A giving approximately 7h of operation is also available. Charging time here is 15h. Weight 6.2kg. The Mains Adaptor type Nor-329A is used for charging the Battery case Nor-330A or the 332A. The charging may take place without disturbing the operation of the Nor-840. The battery box is detachable

Technical Specifications

Analogue inputs Number of channels: 2 (Single ch. version also available) Microphone inputs (2): 7-pin LEMO connectors are standard (B&K type JJ0723 on request) Preamplifier voltage: 120 V, 3 mA to each preamplifier Polarisation voltage: 0,28 or 200 V selectable, ±1% Direct inputs (2): BNC connectors Charge inputs (2): TNC connectors Intensity Input: 18-pin LEMO connector Maximum input signals: 120 V peak (Line and Mic. Inputs) Input impedance: 1 Mohm / 120 pF (all inputs) Input amplifiers Amplifier gain: -40 dB to + 70 dB in 5 dB steps Additional gain: 0-10 dB with accurancy and resolution < 0.1 dB for calibration purposes Measurement range: 0.03µV - 31.6 Vrms. Corresponds to SPL values from -20 dB to +150 dB with a microphone sensitivity of 50 mV/Pa Amplification error: Better than 0.2 dB (20 Hz – 12.5 kHz) Frequency range (AC output): 0.1Hz to 100 kHz with ± 0.5 d.B. 0.05 Hz to 200 kHz with ± 3 dB High-Pass filters: 3-pole Butterworth selectable at 0.63 Hz or 20 Hz (all inputs) Low-Pass filter: 3-pole Butterworth selectable at 2 kHz (charge inputs only) Hum and Noise: Mic. Input:< 10 dB (A), < 15 dB (Lin). Line input: < 0 dB (A), < 3 dB (Lin). Measured with Preamplifier 1201 and dummy microphone. Analogue outputs Wideband outputs (2): BNC connectors. The output signal comes directly from the input amplifiers Output impedance: Max. 10 ohm Output level: ± 10 V peak, 3.16 Vrms corresponds to full scale on display. Outputs are short circuit proof to ground and output current are in excess of 10 mA Analogue to digital converter Converter type: 16 bits linear Sampling rate: 64 kHz (15.625 usec) Filters and networks Anti-aliasing filter: 10-pole Chebychev low-pass filters Frequency range: DC to 27.6 kHz Passband ripple: < 0.1 dB Stopband attenuation: > 75 dB above 1.3 × cut-off frequency. Phase matching: <0.1° for 10Hz - 5kHz., <1.0° for 0.1Hz - 10kHz. Digital filters: 6-pole llR filters for 1/1- and 1/3-octave bands. The 1/3-octave centre frequencies are set with the factor 10n/3 Frequency range: 0.125Hz-16kHz for 1/1-octave bands (centre frequency) 0.1Hz-20kHz for 1/3-octave bands (centre frequency) Filter response: The 1/1- and 1/3-octave filters meet the requirements from EN IEC-61260 class 1 and ANSI S 1.11-1986 Type 1D, Order lll Weighting networks: The true A- and Lin-networks fulfill the requirements to EN IEC 60651 Type 0 and ANSI S 1.4A 1985 Type 0 for precision sound level meters Lin network: 25Hz-16kHz (-0.3dB) 17,8Hz-22.3kHz (-3.0dB) Calculated networks: A-, B-, C- and Lin-networks as well as up to 4 user defined networks may be calculated as a sum of the frequency band within the set frequency limitations. Level detector Detector type: Digital true RMS Resolution: 0.1dB in accordance with EN IEC 60651 and EN IEC 60804 Type 0, as well as ANSI S 1.4A-1985 Type 0 and ANSI S1.43-1997 type 0. Lineavity range: 75 dB (EN IEC 60804 type 0). Pulse range: 78 dB (EN IEC 60804 type 0). Accuracy (20 Hz - 12.5 kHz): + 5 dB above to 60 dB below F.S: <0.2 dB 60 dB to 70 dB below F.S: < 0.4 dB 70 dB to 80 dB below F.S: < 1.0 dB Time constants: Selectable in a binary sequence from 1/16 sec. To 8 sec. Plus I(mpulse). The 1/8 sec. As F(ast), the 1 sec. as S(low) and the I(mpulse) are in accordance with EN IEC 60651 Type 1 and ANSI S 1.4 - 1983 Type 1 Integration period: 4 msec. To 100 hours with 1 msec. Resolution. Crest factor capability: 10 dB crest factor margin at F.S. increasing to 90 dB at 80 dB below F.S. Display Display type: 10.4" bright, back-lit, TFT, VGA colour LCD screen. Picture resolution: 640 (hor.) × 480 (vert.) pixels (VGA standard). Display formats: One or two windows, with or without added information. Each window may individually present data from selectable channel and selectable parameter(s), as a numeric table, as a level vs. frequency graph, or as a level vs. time graph. Displayed range: Selectable to 20, 40, or 80dB. Graphical resolution: 0.1dB - 0.8dB depending on selected format. Numerical resolution: 0.1dB. Numerical range: -99.9dB to +199.9dB. Measurement storage Internal storage: Up 32.000 full frequency single channel spectra. Actual usable number will vary, based on used channels, used registers, used parameters and used frequency range. Floppy-disk: 1.44 Mbyte 3 ½" floppy-drive DOS compatible format gives approximately 250 single mode measurements, or 100 multispectrum measurements each having 1000 periods. Harddisk (optional): Minimum 2.1 Gbyte harddisk MS-DOS compatible format gives approx. 262 500 single mode measurements, or 105 000 multispectra measurements each having 1000 periods. Digital Interfaces Control: Almost any setting or any data readout may be done using the digital interfaces. IEEE-488: Meets the IEEE Standard 488-1978. RS-232C: Meets the RS-232C Standard for normal serial interfaces with handshakes. Printer: Graphic screen-dumps or numeric tables may be printed out using the Centronics parallel interface. Signal Generator Output: BNC connector Output impedance: < 10 ohm (±10 mA) Signal types: Random or Pseudo-Random noise. Spectra: White, Pink, 1/1-octave or 1/3-octave noise. Repetition rate: Approx. 28 minutes corresponding to 0.00006 Hz spectral line separation. Filters: The 1/1- and 1/3-octave filters meets the requirements from EN IEC 61260 class 1 and ANSI 1.11 - 1986 Type 1D. Output level: Selectable in 1 dB steps in the range 0 - 60dB relative to 1 Vrms. General Power requirements: 30 W. 11-15 Vdc. Dimensions: 34×21×35 cm (W×H×D) without battery case. Weight: 9.7 kg without battery (12.3 kg with Battery Case type 330A). Overall performance: The overall performance of the Nor-840 with a suitable microphone and preamplifier, such as the Norsonic Type 1220/1230 and Type 1201, corresponds to the Sound Meter Level Standards EN IEC 60651 Type 1, EN IEC 60804 Type 1, and ANSI S 1.4A - 1985 Type 1. The filter characteristics are designed after the most stringent criteria of the Filter Standard EN IEC 61260 class 1 for analogue and digital filters as well as the ANSI S 1.11 - 1986 Type 1D. The filter also meets the older IEC 225 Filter Standard.