Type 4505-A is a piezoelectric accelerometer, which provides low sensitivity to extraneous environmental effects, a feature achieved through the ThetaShear® design. Type 4505-A has a top-mounted Microdot (10 – 32 UNF) connector for attaching cables and a 10 – 32 UNF-2 A mounting stud on its base. The piezoelectric element used, is the PZ 23 lead zirconate titanate element.
Features
- Low weight
- Low sensitivity to environmental factors
- High resonance frequency
- Electrically insulated for ground-loop protection
- High transverse resonance frequency > 20 kHz
- Operating temperature range – 54 to + 230˚C (– 65 to + 446˚F)
Characteristics
This piezoelectric accelerometer may be treated as a charge source. Its sensitivity is expressed in terms of charge per unit acceleration (pC/g).
The ThetaShear design involves a slotted cylindrical stanchion holding a central seismic mass, flanked by two piezoelectric plates. This assembly is clamped rigidly by the cover. To ensure optimum accuracy and reliability, no bonding agent other than molecular adhesion is required to hold the assembly together. The ThetaShear design provides for a combination of highest measurement stability, excellent sensitivity-to-weight ration and low sensitivity to extraneous environmental effects.
A remarkable feature of the ThetaShear principle is the fact that the transverse resonance frequency is always outside the 10% frequency limit. This ensures minimum interference from orthogonal vibration components in the useful frequency range of the accelerometer. The ThetaShear design also provides excellent immunity to other environmental effects such as base strains, magnetic sensitivity and acoustic fields.
Cabling
When using miniature accelerometers, the cable can affect the measurement result because of forces exerted by the cable on the accelerometer’s connector. This causes amplitude irregularities in the output from the accelerometer at frequencies up to approximately 200 Hz. However, this problem can be reduced by using a flexible cable. To effectively reduce the problem at low frequencies, it is recommended that you clamp the cable. One way of doing this is to make a small loop in the cable close to the accelerometer (maximum diameter 30 mm) and to clamp the cable beside the base of the accelerometer with mounting wax or double-sided tape. This also reduces the possibility of dynamically induced noise being generated by the cable.
Calibration
The sensitivity given in the calibration chart has been measured at 159.2 Hz with an acceleration of 10 g. For a 99.9% confidence level, the accuracy of the factory calibration is ± 2%.
