|Current Location||Sensorica Main Lab|
This is a USB data acquisition device used in prototyping.
Location: CTS, SENSORICA lab.
Ask Tibi and Jonathan
Units are minutes because we consider it as an equipment which is recycled for different projects.
Is part of the pool of shareable
Custodian : SENSORICA
Manager : Tibi (Contact)
Manager : Jonathan (Contact)
|Record created date||Feb. 18, 2013|
|Record created by||None|
We don't know.
Assemble the piezo actuator prototype V3
creating prototype for PMMA joint-type transducer.
prototype the low cost tape sensor, will be taken by Matheus
Worked with Tibi and Jonathan testing the Mosquito enhanced driver
work on this prototype
Assist Nicholas with integration, optical side.
Executed the design, experimented and acquired some data
Work on Photonics for the LED Mosquito in visible
03, JUNE 2013
I discovered this new sensor by playing with the microfiber transducer.
Ideas were there before from discussions with Frederic about the constriction transducer. Frederic thought that the mechanism of the constriction transducer was leakage, and suggested to plunge it in water to see how the signal changes. The microfilament is a constricted optical fiber on a longer length, so the connection was easy to make, I plunged one microfiber transducer into water and it worked.
I also tested it to see a difference between water and alcohol, and it worked. I tested saturated salted water, and the signal difference with pure water was too small to make a conclusion.
I published the results in this video http://youtu.be/oA-0UgrdPBU
I believe that the working principle is leakage: the fiber is pulled to a smaller core, some light transferred into the cladding, which propagates if the fiber is in air. If the fiber is immersed in a fluid with higher refraction index some light escapes. We're measuring intensity fluctuations. So yes, it depends on the difference between the index of refraction of the cladding and the external media. Nothing out of the ordinary. There is some specific know how for the fabrication of the fiber, which has to be tapered and pulled with a certain geometry, the tip has to be melted to a ball and coated with silver (we're using our in-house low cost silver coating method) to send the light back to the detector.
I marked some time for documenting the work, communicating to SENSORICA and publishing it on social media.
I used 125/63.5 MM glass Infinicor300 Corning fiber, pulled with the microsplicer, voltage used 8.5V, max current. I pulled the fiber by hand using the manual micrometers on the device. One can diminish the voltage down to 8V. 7V is not enough to melt the glass fiber. At 8 one can do finer stretches.
The tip of the pulled micro fiber was melted to round it, and was coated using our inhouse wet silver coating method. Only the very tip was coated. I made 2 devices, 1 to 2 mm long, 40 and 20 microns diameter. Only the 20 microns diameter was sensitive when immersed into water.
I used the 850nm LED to test it, before it was improved with filter and amplifier.
TODO: try different diameters. It seems that the critical diameter is between 40 and 20 microns. Also try multiple constrictions to see if we can have a discrete level sensor.
June 17, 2013
See documentation in this doc
The setup was made before, there is another labnote for it.
June 17, 2013
Continued the work. See the Google doc for more details. Jonathan and Antonio were also involved.
We discovered that the analog out of the Labjack is limited to steps of 0.02Volts. We need 0.002Volts resolution, in order to test below 0.5um piezo steps. Jonathan will make a circuit for this.
July 18, 2013
Continued work on characterization. I am doing long acquisitions for precision tests. These results will be entered in the document in the Precision section.
August 01, 2013
Worked with Bing and Antonio on the Piezo. We have a problem with the assembly of the piezo controller. Jonathan made a new prototype and we tested it and it did not work. Frederic's prototype still works fine. We could not clearly understand why the second prototype did not work. The new boards for the product seam to be fine. So the problem is still a mystery.
August 05, 2013
Recreated the characterization setup, because Jonathan had taken the piezo driver prototype away for the fabrication. I modified the way the fiber is attached to the piezo stack.
August 06, 2913
Resumed characterization experiments. I worked on Precision. See more
The long-term stability problem prevents us from directly measure precision. I put a note in the doc and sent message to the team about it.
"This [long-term stability of the Mosquito] is a problem with the acquisition system and with the Mosquito in general that we need to address! We need to improve the architecture of the Mosquito by integrating a reference, which is divided from the signal to account for intensity fluctuations."
I entered the best data here.
One way around the stability is to measure the difference between 0 Volt and the x Volt, "x" representing an input voltage to the piezo controller, which will result in a motion step.
Data still needs to be processed.
Oct 23, 2013,
tested the 2 axis piezo system, driver and the actuator. Worked with Antonio and Jonathan. Produced the piezo manual
Before I start working on this project I review and restructure documentation - website and docs
I also communicated to SENSORICA about my work.
Project page link
Main doc link
There are a lot of docs that need to be updated around the Tape Sensor.
Optical Design - Tape sensor one in (glass) 3 out (PMMA)
with the melted glass fiber tip for a smaller exit cone within the gap.
Received the order from Thorlabs and assembled the optical fibers (3 out 1mm PMMA and 1 in, 125/62.5 glass) together.
It is not easy to assemble these fibers. I attached the together using a think metal wire. I also put them on a metal bar, but I am not too satisfied with that. Need another bar, probably with a groove in it. Also, the gap is not straight, the joint tube is a little too flexible.
The joint tube is a 2mm diameter transparent shrinking tube. No need to shring the tube around, it is tight enough.
I also prototypeed 7 fiber 250um diameter PMMA fiber, using a shrinking tube to hold them together. We already tried this structure using the 1mm PMMA fiber, and it is quite stable. I polished these fibers and it looks good.
I worked with Jonathan on the Tape Sensor.
I assembled the rod, from a cylindrical piece of wood, approx 1m long, which I had so buy. I made a groove in it using the Dremel.
I completed the prototype - glued the optical fibers in the groove of the wooden rod, sanded the rod and inserted it into the aluminum tube. Before inserting it into the aluminum tube we tested the prototype, and it seamed to work well. Some optical fiber preparation (cleaning) was required before connecting the fibers to the PDs and the LED. After the wooden rod was inserted into the aluminum tube I tested the device again. The sensor still works. We need now to find its axis. I also thought about the algorithm to extract the spatial information from the 3 intensities measured on the 3 PMMA collector fibers.
Jonathan helped mounting the PD on the circuit.
Microscopes were used for fiber preparation and for gap alignment inside the groove made in the wooden rod.
I continued to work on the demo for Zhu, which was dues on Friday - the day after.
I wrote the equations to extract spatial information from 3 intensities (need to scan the calculations and put them online!)
See document about the mathematical model and simulations
The LabView program (used for acquisition, data processing and display) required some modification, and the equation needed to be implemented - coded in the LabView program.
After these modifications I moved the setup on a different table that we chose for the demo, and wired everything.
I started testing the device and I encountered some problems. No spatial information could be extracted and the data made no sense within the model we were using.
I tried other ways to extract spatial information from the data, but things did not improve.
I discussed with Ivan and Daniel about the problem, and we realized that our model about the prototype was wrong. It turned out that compression and stretch of the joint were dominating the effects. The mirror tilting was was too small to be detected.
The 3 fibers ware applied off center within the aluminum tube. The intensity fluctuations with vending were max if the bending was done on plane containing the fibers. If the device was rotated fibers were 90 degrees no signal was detected.
So it turns out that this prototype doesn't work as expected, but this gave us other ideas about the hockey stick project (see smart sports equipment).