User`s manual

Biaxial Displacement Follower User’s Manual Version 1.4, April 19, 2004 IM1013

Page

Calibration

Resistors and capacitors have been selected to make the full-scale values on the time constant selector fall within ±5% of the

value indicated. To calibrate the outputs further, it is necessary to move the target or sweep the tracker orthogonal to the

plane of view and at a known velocity, making the output voltage proportional to the velocity or acceleration. The chart

below shows some key frequencies for checking the velocity and acceleration outputs.

Setting

Displacement Output

Frequency

300ms 1.06 Hz

100ms 3.18 Hz

30ms 10.6 Hz

10ms 31.8 Hz

3ms 106 Hz

1ms 318 Hz

0.3ms 1060 Hz

0.1ms 3180 Hz

0.03ms 10600 Hz

Displacement Output Voltage: 4.0V P-P

Velocity Output Voltage: 4.0 V P-P

Acceleration Output Voltage: 8.0 V P-P

System Noise

Since the Velocity/Acceleration unit is a differentiator, its output voltage increases with frequency at the rate of 6 dB/octave

at the velocity output, and 12dB/octave at the acceleration output. The noise input to the differentiator is random with

essentially a flat power spectral density to the filter cut-off frequency. Thus, if the 5100 filter switch is set at

OFF

, and the

time constant selectors are at 300ms, the outputs will be the noisiest. To obtain the best signal-to-noise ratio, set the 5100

output filter to the lowest frequency possible without distorting the displacement waveform. Also, use a lens that is close to

the full-scale displacement expected. Always start at the 0.03ms setting and work back until you obtain approximately a

10V P-P signal. This prevents the output signals from becoming clipped or the amplifiers overloaded.