To verify the accuracy of the calibration of any sensor one needs to know how the sensor works. If you are referring to velocity type vibration pick-ups (sensors), commonly called "seismic" vibration pick-ups, they have a small weight suspended from the top of the sensor housing with a spring. There is a magnet (permanent magnet) on that weight and a coil surrounding the permanent magnet in the housing. When the sensor is "shaken" (vertically up and down) the permanent magnet moves and generates a small voltage in the stationary coil, the magnitude of which is a function of the movement of the permanent magnet/weight which is a function of the force caused by the vibration: more movement, more voltage.
The output is scaled, usually in millivolts/unit of measure (in/sec, or mm/sec, for example).
None of the velocity vibration pick-ups I have worked on had an ability to adjust the sensitivity of the output. So, this idea of "calibrating" velocity vibration pick-ups is incorrect. The best one can do is to find what's commonly called a "shaker table", which has the ability to generate a variable amount of vertical movement at some frequency, mount the vibration sensor on the table, and measure the output versus the applied movement ("vibration"). It's a pass or fail test--either the output is proportional to the applied movement of the shaker table, or it's not. There's no adjustment on the vibration sensor.
To test linearity of the sensor output, one usually applies several different "vibrations" from the shaker table and records--then analyzes--the sensor output to ensure it's linear.
But, there's no "calibration" to be done--presuming we are talking about the majority of velocity (seismic) vibration pick-ups.
If the turbine at your site uses another type of vibration sensor (proximity, or accelerometer) then one has to understand how the sensor works and then find the appropriate "simulator" to measure output. But, in both of these cases (proximity and accelerometer) I've never encountered sensors with adjustment, either. One can only check that the output is as per specification by applying a simulated input, and verify linearity. But, an adjustment cannot be made to the scaling/sensitivity of the devices.
Most device manufacturers have some information on their website about testing methods or criteria. And, if the don't--they usually have some descriptions of how their sensors work that can be used to devise a test.
But, to the best of my knowledge the overwhelming majority of vibrations sensors (of just about every common type) cannot be "calibrated" in the field like a pressure switch or temperature transmitter can be calibrated. There's no adjustment of sensitivity or zero or span or scaling--it is what it is. And, if a test determines the output is not linear or the device is not producing the specified output per input then it must be replaced.
Hope this helps!