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ventilation hole on microphone preamplifier

Technical Note
Why are there small holes on the preamplifier?
Vent holes allow for equalization of the external pressure. This also impacts the low frequency specification. If the preamplifier vent hole gets covered or sealed, the microphone will not work properly.

A microphone holder can block this vent. A short preamplifier has very little surface area to clamp onto, so there is a higher probability of blocking the vent. This is why a second vent hole on a different axis was added to PCB short preamplifier 426A07 (1/4") and 426A13 (1/2")
PCB DC/AC coupled signal conditoner

Technical Note
What is the use of DC coupling on a ICP Signal Conditoner (Amplifier)?

AC coupling is normally used in ICP Signal Conditioner to block the DC signal of the power supply (to the transducer). AC couping is by means of high pass filter, which inevitably affects the time constant of the measurement circuit.

When DC coupling is used, the DC signal is eliminated electronically inside the signal conditoner. Without the high pass filter, the time constant (DTC) is solely contributed by the sensor itself; and can be very long, for example, 100 second. That can be used to measure a step force signal quite accurately.

Example : an 100 N force is measured with a force transducer with 100 s time constant (DTC). In 10 second (10% of DTC), the measured force decays 10%. In 1s (1% of DTC), the measured force decays only 1%, so accurate force reading can be made in short time after the force applied.

Learn more about PCB DC/AC coupled Signal Conditioner 482C24

HBM : Stress & fatique measurement

Applicaton Introduction
Fatigue Test of Materials and Structures

Driven by the need to increase the energy efficiency of vehicles and machines, lightweight construction of mechanical parts and components need to go close to the fatigue life limits of established or new materials. Nevertheless, for safety relevant structural components such as vehicle axes and wheels, a fatigue failure during operation must be excluded by all means. Likewise, a fatigue failure of critical functional components such as crank shafts or connecting rods leading to a defect of the entire vehicle or machine must also be avoided.

Learn more about fatique and durability test by HBM

Product Profolio
Class 1 Sound Level Meter
Noise Dosimeter
Noise Analyzer 1/1, 1/3 Oct
Permannent Noise Monitoring 
NC, NR, STI, Reverberation Time
Outdoor Microphone
Noise Mapping
Data Acquistion System
Sound Calibrator
Audiometer Calibration System
Acoustics Coupler
ISO 10816-1 Vibration Meter
Vibration Analyzer
Vibration Data Collector
Vibration Monitoring System
Vibration Transmitter 4-20 mA
Vibration Indicator
On-line Vibration Monitoring
Vibration Switch

Modal Analysis System
Vibration Controller
Vibration Testing System

Shaker, Exciter
Vibration Calibrator
Ground Vibration Monitor
Impact Hammer
Pressure Transducer
Strain Gage

Load Cell
Force Transducer
Torque Transducer
Displacement Transducer

ICP Signal Conditoner
Bridge Signal Conditoner
Measuring Amplifier

High Voltage Testing
High Speed Electrial Power Measuring System

iTestMeasure Co. Ltd.
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Featured Products : 831 Sound Level Meter; Vibro M Vibration Meter / Analyzer
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