Bruel Kjaer Calibration Exciter type 4290

USED.. good condition in original wooden case.

The Calibration Exciter Type 4290 is an electrodynamic vibration exciter designed to vibrate accelerometers or small components at variable frequency in the range 200 Hz to 50 kHz. This range, with reliable acceleration control up to 30 kHz, makes the Calibration Exciter a useful reference device in high frequency vibration work.

The Exciter consists of two separate parts, a cylindrical permanent magnet and a small compact moving element with built-in control accelerometer. When the moving element is placed onto the core of the permanent magnet, the drive coil is situated in the radial magnetic field produced by the magnet. Suitable suspension is obtained by simply inserting a disc of foam nylon between the moving element and the magnet core. (This type of floating suspension has no transverse resonance in the frequency range of the calibration exciter.) The suspension resonance occurs at 30 to 100 Hz. Small dimensions, extreme compactness and rigid construction, give the moving element an outstandingly high first resonant frequency: above 50 kHz. The built in control accelerometer, which has a mounted resonant frequency around 60 to 70 kHz, follows exactly the movement of the table, and the output signal is used to control and monitor the acceleration at the table surface. The exciter will be driven by a sine/noise generator through a power amplifier. The maximum force output which is around 3N (0.675lbf) peak is obtained with a power of 2.5W. The acceleration level obtained with a typical 30g accelerometer is of the order 1ms–2 (0.1g) which is sufficient for calibration of piezoelectric accelerometers. The calibration exciter can be used in environmental test chambers in a range from 0 to 80°C (32 to 176°F).