Rotary Chair Nydiag 200
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Conversion of Frequency to Acceleration
In order to avoid exceeding the maximum acceleration performance during higher frequencies of Slow
Harmonics Acceleration Testing, please refer to the following conversion table for observation of upper
limits:
Frequency
Acceleration @ Peak
Velocity 60º/s
Acceleration @ Peak
Velocity 50º/s
Acceleration @ Peak
Velocity 40º/s
Hz
º/s²
º/s²
º/s²
0.01
3.8
3.1
2.5
0.02
7.5
6.3
5.0
0.04
15.1
12.6
10.1
0.08
30.2
25.1
20.1
0.16
60.3
50.3
40.2
0.32
Not possible
100.5
80.4
SHAT test
For the SHAT test the frequency increases after each period. A commonly used procedure employs
oscillation frequencies of 0.01, 0.02, 0.04, 0.08, 0.16 and 0.32 with peak angular velocities of 50º/sec
at each frequency. The patient undergoes multiple cycles of oscillation at each frequency.
Testing the Sinusoidal Function:
Velocity °/s
–
peak angular velocity between turning points
Frequency Hz
–
duration of cycles between turning points/cycles
Frequency change
–
steady or changing period length for each cycle
Velocity change
–
steady or changing velocity for each cycle
Number of cycles
The various parameters of the sinusoidal test are difficult to test objectively. Apart from the number of
cycles that can be counted, only subjective assessment is possible:
1.
Velocity: does the chair move faster with increasing values for velocity? Compare values
20°/s with 50°/s
–
with Frequency Hz, Frequency change df and Velocity Change dv = 1
2.
Frequency: With velocity fixed at a given value, does the period length increase with
decreasing values for Frequency Hz? Compare
with values „0,10‟ and „0,02‟ in the
Frequency Hz
box and press “Start” –
at „0.10‟ the period should be shorter than at „0.02‟
3.
Frequency Change: values > 1 produce smaller cycles in terms of degrees rotated, whereas
values < 1 produce longer cycles in terms of degrees rotated
4.
Velocity Change dv: values >1 produce faster movements whereas values >1 produce slower
movements
5.
Cycles: check that the chair rotates the number of cycles ordered. One cycle is half the
pendular movement; i.e. from zero, acceleration phase and then de-acceleration into zero
again.