SVAN A DESCRIPTION OF GROUND VIBRATION FUNCTION. SVANTEK Sp. z o.o. WARSAW, July 2014 SVANTEK

Transcription

1 SVAN A DESCRIPTION OF GROUND VIBRATION FUNCTION SVANTEK Sp. z o.o. WARSAW, July 2014 SVANTEK

2 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 2 Note: The ground vibration mode may require FFT analysis and Wave recording options to be activated in instrument to fully comply to DIN standard. To activate options the payable code is necessary. Part 1. General configuration of instrument. 1) Perform instrument calibration 2) In measurement function select Ground Vibrations 3) Enter menu Input / Measurement Setup Start Delay is the delay after pressing the Start button before instrument starts to measure. Integration Period is time for which results will be averaged. For example if 30 seconds is selected, PEAK value in main results will represent the highest value obtained within 30 seconds of measurement. Selection of Integration period: INF (infinity) measurement runs until STOP is pressed.

3 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 3 Cycle number defines how many times integration time will be repeated. Selection of Inf mean that instrument will repeat Integration Periods until Stop is pressed. Logger step is the period of integration for time history results which is the second available integration step. If 2s is selected then PEAK value in time history will represent the highest sample value from 2s. Spectrum enables frequency analysis used for defining the significant frequency. Next step is Channels Setup configuration:

4 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 4 Channels setup allows to configure 2 independent profiles. General setup allows to configure independent weighting filters (acceleration, velocity or displacement) in each of 3 vibration channels and configuration for sound measurement in fourth channel. Range should be selected in accordance to expected vibration levels m/s2 and 316 m/s2 are names standing for LOW and HIGH. The range actual values depend on the type of sensor used. In case of overloads in the signal the range should be set to higher value. Filter represents weighing used in selected channel. Typical settings for effect of vibration on humans in buildings uses Wm weighting (in accordance to ISO ). The 4 th channel allows to record sound in the full frequency band (20kHz) in accordance to Class 1 IEC Range 105dB and 130dB stands for LOW and HIGH ranges. In case of overloads in the signal the higher range should be selected. Usage of 3 profiles allows to define independent weighting filters that will apply to measured sound signal simultaneously. 4) Channels Setup/Ground Vibration settings

5 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 5 Band defines frequency band for the Profile 2 results. In case 175 Hz selection the results and frequency analysis will be performed within range of 175 Hz. Filter stands for weighing in vibration channels (1-3). Typically VEL1 filter is used for evaluation on effects on structures in velocity units. Depending on the self-noise of used sensor it may be more appropriate to use VEL3 filter (number stands for cut-off frequency). 5) Enter Logger Setup to define which results will be recorded to time history. Sample screens below show activation of recording in Channel 1 of RMS and VDV in profile 1 (Wm weighting) and PEAK velocity (VEL1 weighting) values in Profile 2 and short LEQ values in Channel 4 (all profiles selected). Selection of Vector in Auxiliary logger will enable recording of Peak Vector calculated from vibration channels (1-3).

6 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 6 6) Enter Wave parameters to enable Time Domain Signal Recording to USB disk. Note: USB disk should be connected to the instrument. It is necessary to format USB disk as FAT-32 prior to usage. The maximum wave file size is 4GB due to the FAT-32 format. Wave format Extensible is created by Microsoft. The majority of programs accept PCM format. Wave samples are recorded as velocity if ticked. Write Mode Safe defines the level of security of recordings to USB disk. 7) Enter FFT Setup to define its parameters: In order to save FFT spectrum for each logger step select logger RMS.

7 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 7 8) Auto-save in order to record Main Results the auto-save function has to be activated: set to NUMBER. NOTE: Auto-save files are additional type of files written separately to the time history (logger) files. In case of short integration period auto-save function will not be possible to use. Minimum Integration period for auto-save function in ground vibration mode is 30 seconds. Part 2. Triggers To enable triggers enter menu Input/Trigger setup/measure Trigger Selection of trigger Level+ will record until the signal stays above the threshold level. Source VEC/SND indicates that triggers are based either on vector from 3 axis or noise level in the 4 th channel When triggers are set press Start in order to begin. The red icon in the top bar will indicate that instrument is waiting for triggrer in order to start recording.

8 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 8 Part 3. Working with data files in SvanPC++. SVAN 958a records two types of files: - Main Results (begins - contains results for each integration period if auto-save is enabled - Buffer files (sometimes named as logger file or time-history files), contains short results integrated with logger step

9 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 9 Main result file contains spectra for the integration time period: Along with the results:

10 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 10 Buffer file (logger results) contains info on time history. In case trigger were used time history will contain breaks and values for the periods when conditions triggrer were met. In this guide logger has been set to record spectrum FFT thereofe for each logger step the spectrum has been recorded. SvanPC++ enables to synchronize both views and display related spectrum to the logger values:

11 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 11 Part 4. Compatibility with DIN standard. Following table is a the basis of the standardized measurements at building foundation: The table is also shown as a graph where poits are connected by straight lines indicating values for each frequencies for example, for dwelling (line 2) at 16.5 Hz it is 6.6 mm/s

12 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 12 The basis of the standard is PEAK measurements: Following standard we need to find Peak and define significatnt frequency using FFT with Hanning window. To find significant frequency and the signal character we follow App. D of the standard:

13 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 13 Appendix D: So called event is between to dashed lines and it is presented in enlargement on the next graph.

14 SVAN 958A DESCRIPTION OF GROUND VIBRATION FUNCTION 14 Standard uses FFT with Hanning window for the time of the event: The FFT indicates significant frequency in this example 16.5 Hz which should be compared with Table 1: