Characterization tests - preliminary results

posted Oct 4, 2012, 6:44 AM by Tiberius Brastaviceanu   [ updated May 23, 2013, 9:17 PM ]

We have performed the first characterization tests on the Joint-type transducer. 



Two joint-type transducers
finished transducers

Stiffness measurements

Ivan and James have performed stiffness measurements. The graph below shows a linear fit of Force [nN] vs Displacement [um]. The Force is applied at the tip of the lever in a direction perpendicular to the axis of the optical fiber transducer, by attaching different per-calibrated weights. Displacement is the displacement of the tip of the lever under these weights. In this case, the lever is 22mm long. Weights were attached very close to the tip. We obtain for this particular joint-type transducer 197.35 nN/um.
First stiffness measurement of the joint-type transducer using calibrated weights attached to the lever. The result is 197.36nN/um for a lever 2.2cm long
Optical fiber/lever with weight attached to it


Optical fiber/lever with weight attached to it and the optical fiber
in  the relaxed position on top (two pictures superposed)



Displacement vs Voltage signal

NOTE: we realized that there was an error of reading on the micrometer. Ask Tibi to correct the data!!

[Experiment performed and analyzed by Tibi] In this experiment the transducer was pushed with a micrometer in 1um steps, in a direction perpendicular to its axis (pure bending mode of operation) and the voltage was recorded. 500000 samples were acquired at 126kHz and averaged for each data point on the graphs below. For all graphs the displacement needs to be multiplied by 10, i.e. 1 is 10 microns and 12 is 120 microns. 

Voltage [Volt] vs Displacement [10um]
Displacement Calibration curve, plotting voltage vs displacement of the tip of the optical fiber transducer. This was done on a joint-type transducer, 22mm long lever. 500000 points were averaged at 126000points/sec rate. The lever of the The position needs to be divided by 10, i.e. 1 is 10 microns, 12 is 120 microns...
For a 22mm long lever. The resolution is well above 1 micron. Almost linear on 600 microns 


Voltage [Volt] vs Displacement [10um]
Displacement Calibration curve, plotting voltage vs displacement of the tip of the optical fiber transducer. This was done on a joint-type transducer, 10mm long lever. 500000 points were averaged at 126000points/sec rate. The lever of the The position needs to be divided by 10, i.e. 1 is 10 microns, 12 is 120 microns...
For a 10mm long lever. The resolution is very close to 1 micron. Linearity on 40 microns distance.


This particular joint-type transducer exhibited a strong directionality and unwanted structures. We attribute that to the poor quality of the mirror (silver coating). Transducer 4 was used in this particular experiment.

20X picture of the mirror (on the tip of the lever) of transducer 4

The graph below is recorded with the same transducer but in a different orientation (a rotation around the axis of the transducer). In this case the lever is only 5mm long. On the ascending part we can see that the resolution is below 1 micron (every next point is above the previous one). The small shoulder in the middle of the ascending part is a real feature. See next graph. 


Voltage [Volt] vs Displacement [10um]
Displacement Calibration curve, plotting voltage vs displacement of the tip of the optical fiber transducer. This was done on a joint-type transducer, 5mm long lever. 500000 points were averaged at 126000points/sec rate. The lever of the The position needs to be divided by 10, i.e. 1 is 10 microns, 12 is 120 microns...
For a 5mm long lever. The resolution is under 1 micron. Linearity on 50 microns distance after the first feature.

The graph below illustrated the complexity of the signal. The orientation of the transducer was modified again (rotated on its axis). The lever  in this case is 5mm (distance between point of contact and gap). As the transducer is pushed in one direction the signal diminishes (contrary to the two cases above), reaches a minimum and increases again. the structure close to the minimum is NOT noise, suggesting that this is a real structure in the spatial intensity distribution of the light that reflects from the mirror. 

Voltage [Volt] vs Displacement [10um]
Displacement Calibration curve, plotting voltage vs displacement of the tip of the optical fiber transducer. This was done on a joint-type transducer, 5mm long lever. 500000 points were averaged at 126000points/sec rate. The lever of the The position needs to be divided by 10, i.e. 1 is 10 microns, 12 is 120 microns...

CONCLUSION
Need to better control silver deposition and to control the cleaving process, in order to obtain a perpendicular cut.

Free oscillations of a 22mm long lever of a joint-type transducer

[Experiment performed and analyzed by TibiThe picture below shows free (dumped) oscillations (in air) of the joint-type transducer. The oscillation period for this 22mm long lever is around 6.79ms.




Comments