To All,
I currently have 12 on-line accelerometers and will be adding 36 more shortly. How often should these be checked against a shaker table for proper operation and values. We were fortunate enough to have budgeted for a PCB hand held unit and we check accelerometers semi annual.

Also, how far out of range from spec can an accelerometer be before false values corrupt the trend line. During the most recent audit I found one to be .178 short of the calibrated 1g at the predetermined frequency (159.3) of the shaker.
Any Thoughts’

My experience shows the spectra will tell you if there is a problem. If you are doing it for ISO then you have to follow the manufactures recommendation. I haven't checked lately but that use to be once per year on ceramics and every five for crystal.