Technical Reliability and Validity of the CSA Accelerometer: Should We Recalibrate or Re-Think?

Purpose To study the mica- and inter-instrument reliability and validity of the Computer Science & Applications (CSA) Model 7164 accelerometer, along with the nature of the analogue filter in the device with sinusoidal movements in a mechanical setting.

Methods Six CSA units were tested with 17 different frequencies (0.5-4Hz) on three radius settings (0.022-0.049m), yielding 51 different acceleration settings (0.1-19.7 rrvs^-2).

Results Intra-instrument reliability was relatively good (mean CV of 4.4%), although questionable on extreme values of acceleration (<1ms^-2 and >16ms^-2). Analyses on inter-instrument reliability revealed both overall systematic bias and acceleration- specific differences between units, approaching unit error magnitudes of 20% from the mean of all 6 units. The correlation between CSA output and acceleration (Le., validity) was significant but the relationship was clearly nonlinear. Applying equations to cancel the frequency-dependent filtering restored this linearity (r2 = 0.97).

Conclusion The CSA exhibits reasonable intra-instrument reliability but large unit differences call for unit-specific calibration or alternatively statistical adjustment. Linearity between CSA output and acceleration is achieved only by correcting for movement frequency filtering.