Metroacúsica PXI System
Metroacústica PXI system uses software developed in LabVIEW language that works in conjunction with the hardware for signal generation and acquisition, consisting of a board specifically designed for sound and vibration applications.
The PXI system offers proprietary software for calibration of the following equipment:
- old sound level meters - software "IEC60651pxi.exe"
- new sound level meters - software "IEC61672pxi.exe"
- sound exposure meters - software "IEC61252pxi.exe"
- noise dosimeters - software "ANSI_S125pxi.exe"
- sound level calibrators - software "IEC60942pxi.exe"
- measuring microphones - software "IEC61094pxi.exe" (under development)
Our PXI System has a calibration certificate issued by INMETRO !!!
The system is based on the use of a PXI-4461 generation / acquisition board from the National Instruments manufacturer. This board has output 3 gains that generate signals from 10E-6 Vpk up to 10 Vpk with high accuracy, making it an excellent device to generate the normalized signals for the calibrations of sound level meters, noise dosimeters and sound exposure meters.
Its 6 output gains make it an excellent device for calibrating sound calibrators, measuring microphones, and it also can measure low amplitude signals such as self-generated acoustic noise.
Every software is an executable application and for programs to run correctly it must be used template spreadsheets. In these worksheets, some characteristics of the equipment to be calibrated, such as its measurement ranges and reference level, must be selected prior to the start of calibration.
The guideline document DOQ-CGCRE-052 of the General Coordination of Accreditation (CGCRE) of the National Institute of Metrology (INMETRO), provides a list with the recommended minimum requirements to be checked when calibrating some electroacoustic equipment in Brazil.
The software "IEC60651pxi.exe" generates the normalized signals for the following calibration tests of old sound level meters:
1. Linearity Level
2. Frequency Weighting (A, C and LIN)
3. Time Weighting (Fast, Slow and Impulse)
4. RMS Detector
5. Time Average (LAeq) - IEC 60804 test
The software "IEC61672pxi.exe" performs generation / measurement of the standard signals for the following calibration tests of new sound level meters:
1.Self-generated acoustic noise
2. Linearity level in the reference range
3. Linearity Level including range control
4. Response to tone burts (Fast, Slow, SEL and LAeq)
5. Frequency weighting (A, C and Z)
6. Frequency and time weightings at 1 kHz
7. Overload indication
8. C-weighted peak level
9. Long-term stability
10. Stability at high level
11. Acoustic test with the microphone attached
The software "IEC61252pxi.exe" generates normalized signals for the following calibration tests of sound exposure meters:
1. Level Linearity
2. A Frequency weighting
3. Response to short-duration signals
4. Response to unipolar pulses
The software "ANSI_S125pxi.exe" generates the normalized signals for the following tests of the calibration of noise dosimeters:
1. Level Linearity
2. Frequency weighting (A, C and Lin)
3. RMS Detector - ANSI S1.4 Test
4. Time weighting (Fast and Slow) - ANSI S1.4 test
5. Time Average (LAvg)
6. DOSE (%) - Stationary Signal
7. DOSE (%) - Pulse Signal
The software "IEC60942pxi.exe" performs the measurement of the standard signals for the following calibration tests of sound level calibrators:
1. Level
2. Frequency
3. Harmonic or Total Distortion
The software "IEC61094pxi.exe" is still under development and will carry out measurement of the standard signals for the following calibration tests of measuring microphones:
1. Frequency response
2. Sensitivity
For the elaboration of the Metroacústica PXI System the following documents were used as reference:
NI PXI 4461 Board Manual
NBR ISO / IEC 17025: 2005 - General Requirements for Competence of Testing and Calibration Laboratories.
IEC 60651: 1979 - "Electroacoustics - Sound Level Meters".
IEC 60804: 1985 - "Electroacoustics - Integrating-averaging Sound Level Meters".
IEC 60942: 2003 - "Sound Calibrators".
IEC 61672-1: 2013 - Sound level meters - Specifications
IEC 61672-3: 2013 - Sound level meters - Periodic tests
IEC 61252: 1993 - Sound Exposure Meters
ANSI S1.25: 1991 - "Specification for personal noise dosemeters".
ANSI S1.4: 1983 - "Specification for sound level meters".
Guide for the expression of measurement uncertainty - GUM, 2003, Third edition in Portuguese language.
VIM International Vocabulary of Metrology - Fundamental and General Concepts and Associated Terms, 1st edition Luso-Brazilian, 2012
DOQ-CGCRE-052 - Guidance for calibration of acoustic measurement devices