Construction of the Full-Scale Tagger Microscope

Preparations for Construction of the Full-Scale Tagger Microscope

Current Work

• Determine an ideal process to assemble components of the fiber splicing unit.

• Optimize and document a reliable, repeatable process for fusing 2mm x 2mm square optical fibers using a fiber splicing unit.

• Work with James McIntyre to develop polishing, gluing, painting, and quality assurance procedures for optical fibers.

• Develop/refine a LabView program that controls a water heater and water pump based on water temperature.

A List of Specifications/Manuals for Items in Lab 405

Data Acquisition Hardware

Net Booter Quick Start Pamphlet

Net Booter User Manual

Water Pump

Water Heater

Three way sweat valve

Black Silicone Adhesive (RTV)

Ultra Black Silicone Adhesive (gasket maker)

Polystyrene

Pictures

From Summer 2012:

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  Preparing for construction.

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  Just before the shelving was erected.

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  Construction of the tank to be used in fiber bending.

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  Testing the strength of the tank.

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  testing...

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  Here it is easy to see the bowing from water pressure.

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  Tank with wooden supports.

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  Tank with support and insulation. Plumbing and hot water testing are the next goals.

LabView Program

During the summer of 2012, Ben Willis wrote a LabView program that would communicate with a NetBooter and ultimately control a heater and water pump. LabView also plots the temperature of water being heated, and plots the changing temperatures on a graph on the front panel. Before Ben left, he wrote a final report of his work on the program and in the lab in general. I have added a little to Ben's work, mostly housekeeping; deleting some non functioning commands, adding the equation to represent temperature based on voltage, adding an equation for a thermocouple, and connecting with the DAQ. I also plan to make a differential op-amp to allow the DAQ to read the inputs given by the thermocouple. In this way, we will be able to use a thermistor and two thermocouples to control the water temperature in both the straightening pipe and the bending tank.

I had found a lab manual from the University of Minnesota that gave step by step instructions for taking and recording temperature measurements using a thermistor, a DAQ, and LabView. After making the circuit and updating the LabView program it seems to be working within expected error.

The Lab Manual

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  The front panel of the LabView program.

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  Part 1 of the block diagram: The majority of this part of the program is to read the output given by the DAQ, translate it to a temperature, and plot the results.

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  Part 2 of the block diagram: The main purpose of this part of the program is to determine if the temperature read from part 1 is what was specified in the front panel, and to turn the water pump and heater on or off as appropriate.

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  A view of the LabView front panel that Ben and I created. The voltage and temperature are actual readings/calculations that have been made.

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  A view of the lab that inspired the thermistor idea. The numbers are a close comparison of the measured data in the previous picture.

Temperature Measurements

Along with the LabView program, another component of bending fibers will be to determine the temperature of the water and to make that information available to the program.

At first, I had thought that our best bet as far as reading/recording water temperature was to make a thermistor (as seen below).

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  A temperature measuring circuit that included a voltage divider, a resistor, and a thermistor.

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  This is the same circuit as to the left, except it is free of a breadboard and water resistant.

Although this thermistor is reasonably accurate, I feel that it would be possible to have (already purchased) thermocouples read the temperature instead. The signal from the thermocouple would need to be amplified in order to be read by the DAQ we are currently using because the thermocouple produces voltages in the micro range. Using an operational amplifier and the right resistors I am confident that I would be able to achieve a strong enough signal from the thermocouple(given enough time). The remaining hurdle in this endeavor would be to tweak the LabView program to use the temperature-voltage relationship equation of a type J thermocouple instead of a thermistor.

Some great resources for thermocouple theory and circuitry can be found here:

The Basics of Thermocouples

Thermocouple Application

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  I feel that this is a place to start if I am to accurately read a thermocouple. Included in the circuit diagram is cold junction compensation and signal amplification; two things that are a requisite to accurate measurements.

After reading the material above, I have found two (cheap) ways to read a thermocouple accurately:

1. Create something in the software that compensates for the room temperature factor at the cold junction. If we end up using the thermistor to read the temperature at the cold junction then we will be introducing the error from one temperature measurement to another. Although the thermistor will read the water temperature within acceptable error, adding more error into the calculation seems unnecessary to me.

2. Follow the diagram above and create a hardware approach to cold junction compensation. After determining the voltage output of a type J thermocouple at zero degrees Celsius, I can introduce that voltage at the cold junction site. By following the circuit above, I would probably be able to construct a circuit that would have cold junction compensation and amplification for the signal. My concerns for this approach involve time constraints and the intricacies of this setup.

Completed Work

• Clean and organize room P405.
• Hot water tank constructed - still awaiting testing
• Splicing unit collars redesigned
• A program was written to automatically control a heater/pump based on the temperature of the water.

Lab Journal

In the past I had kept my journal in a Google Document.