A combination of high sensitivity, low mass and small dimensions make Types 4506, 4506-B, -B-002 and -B-003 ideally suited for triaxial modal analysis measurements of composite structures that require multiple measurement points, for example, automotive body and power-train measurements, or modal analysis on aircraft, trains and satellites.
The slots in the accelerometer housing allow easy mounting on five sides using inexpensive plastic clips that fit easily to the test object.The family of DeltaTron Accelerometers Types 4506 are miniature triaxial piezoelectric accelerometers housed in robust titanium with a single integrated Microtech compatible connector.
Anwendungen
- Structural analysis measurements
- Multichannel modal analysis measurements
- Modal measurements for automotive body and power-train applications
Merkmale
- ID (TEDS) "Smart Transducer Interface" IEEE P1451.4
- Five mounting surfaces
- Easily fitted to different test objects using a selection of mounting clips
- Robust titanium housing with integrated titanium 4-pin connector
- Compact, patented OrthoShear® design giving high sensitivity/weight ratio. The unique uni-mass construction ensures that all axes have the same point of reference
- Connects directly to DeltaTron power supply (ICP® compatible). The DeltaTron® principle allows the use of inexpensive cables
- Low output impedance enables the use of long cables
- Built-in low-noise preamplifiers with ASICs for a dynamic range exceeding 100 dB (100 mV/g sensitivity)
- Electrically insulated for ground loop protection
Design
Normally, triaxial accelerometers consist of three individual accelerometers mounted in a single housing and positioned so that vibration can be measured in three mutually perpendicular directions. This approach sets limits to reducing the size of the accelerometer and also means that the three axes have different points of reference.
The OrthoShear design used in Type 4506 is built around a common seismic mass. This uni-mass design results in a very compact triaxial accelerometer where all the axes have the same point of reference. The design also ensures accurate and consistent measurements, even when the accelerometer is exposed to complex vibration patterns. The seismic mass is surrounded by a piezoelectric ring which is surrounded by four individually suspended, curved plates. Because of the suspension pins, different sections are exposed to shear forces for different directions of acceleration.
By appropriate summation of the signals, the outputs for the X, Y and Z axes are obtained. The assembly is clamped together by the outer ring. The preamplifiers, suspension pins and Microtech-compatible connector constitute an integral part which is hermetically welded to the titanium housing. Type 4506 is internally insulated from the housing. The risk of ground loops, which can be particularly troublesome in multichannel measurements, is therefore reduced considerably.
Frequency Response
The following information on frequency response is included on each accelerometer’s accompanying calibration chart. However, Types 4506 B, 4506 B002 and 4506 B 003 have this information built-in electronically (TEDS) as well.
The upper frequency limits given in the specifications are the frequencies where the deviation from the reference sensitivity is less than 10%. It is approximately 30% of the mounted resonance frequency. This assumes that the accelerometer is correctly mounted onto the test structure – a poor mounting can have a marked effect on the mounted resonance frequency.
The lower frequency limits and phase response are determined by the built-in preamplifiers. The lower frequency limits are given in the specifications for deviations from reference sensitivity of less than 10%.
Increased measurement accuracy can be achieved by dividing the actual measurement with the individual frequency response.
The calibration chart includes the individual TEDS values that, together with a general formula, best fit the measured frequency response. The expression can be used for frequency response compensation in the specified frequency range.
Calibration
Each Type 4506 is individually calibrated and supplied with a comprehensive calibration chart. Long-term stability and reliability are ensured by artificial ageing during the production process. Field checking and system calibration are straightforward using Brüel & Kjær’s hand-held Vibration Calibrator Type 4294.
Subsequent Calibration
Brüel & Kjær manufactures a range of equipment for frequency response, sensitivity and system calibrations.
