How do I know that the reading is correct and accurate?

The best way to check if the readings are correct/accurate is to use a calibrator. Calibrator is a device that produces known vibration, typically at one of few different frequencies. The Digiducer (or any accelerometer) can be mounted on such a calibrator and readings are taken. Results are compared to what calibrator is set to. This is how we check the accuracy of the system.

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So far, there has not been found accelerometer that has incorrect calibration form the factory (Modal Shop), so there has not been a need to change calibration in the header of the accelerometer.

If the client is using an external ICP accelerometer connected to digital ICP ( 485B39 ) then the process is different. The ordinary accelerometer ICP accelerometer is attached to the calibrator, then the signal is digitised with the 485B39 and readings taken by our app. In this case, the user can enter in our app whatever sensitivity will give them the correct reading. Default is 100mv/g.