APPLICATION NOTE: Laser Triangulation Sensors - MTI Instruments ...

MTII’s laser triangulation systems have software adjustable low pass filters for easy
adjustment in the field.
Figure 6: Amplifier Output Noise with 20kHz Low Pass Filter
Figure 7: Amplifier Output Noise with 100Hz Low Pass Filter
MTII’s laser sensors also provide displacement values in digital formats. Digital output
resolution is calculated by dividing the displacement range by the processor bit rate. For
example, a sensor with a 2000 micron range would have a resolution of 2000/2E16, or
0.03 microns for a 16 bit system. If using a 12 bit converter the resolution would be
worse at 2000/2E12, or 0.5 microns.
v.) Bandwidth
The bandwidth, or cutoff frequency, of a system is typically defined as the point where
the output is dampened by -3dB. This is approximately equal to an output voltage drop of
30% of the actual value. In other words, if a target is vibrating with an amplitude of 1mm
at 5kHz, and the bandwidth of the laser sensor is set at 5 kHz, the actual output would be
1mm X 70% = 0.70mm. So, it is important to set the system’s frequency response higher
than the expected target motion. All of MTII’s laser sensors have adjustable filter
settings. The appropriate filter should be selected for the application to prevent any
attenuation of the output. MTII’s Application Engineers can assist in selecting
appropriate filter settings.