For many applications tactile measurements are not suitable or even not possible. For high or low temperature measurements e.g. no sensor system can be installed in the test chamber. Non-contact measurements are also of great importance for vibration analysis: Especially for small and lightweight components, the dynamics of the components is changed by the additional mass of the sensors to a non admissible extend.

DTSquare uses two type of laser based non-contact measurements:

Laser-Triangulation

Laser Triangulation is based on locating the hitting point of a laser beam, reflected by the measurement object, on the sensor head. The hitting point of the reflected beam varies with the distance between sender/receiver and measurement object. Triangulation sensors provide a resolution up to 1 micrometer and cover a frequency range up to 10kHz. For higher frequencies the deflections ar usually too small, so that laser-doppler-vibrometry is the more admissible method.

Laser-Doppler-Vibrometry

The measurement of vibrations with the laser-vibrometer makes use of the so-called "Doppler"-effect, which means that the wavelength detected by the receiver varies with the relative velocity between sender and receiver. The laser beam is sent at a fixed frequency by the vibrometer head, reflected at the specimen and received again by the vibrometer head. The relative velocity, caused by vibrations of the specimen can be detected by evaluating the frequency shift between sent and received laser beam.

Laser vibromety can be used up to very high frequencies of several hundred Kilohertz, and for the very small deflecions, which are typical for high frequency vibvrations. Based on it's functional principle, the vibrometer measures vibration velocities and is therefore less suitable for measuring long-term non-osciullating movements (drift effects). Laser vibrometry is especially well-suited for measuring multiple points in modal analysis.