5G50.51 - R vs. T in a Superconducting Disk
Demonstrate the resistance of a superconductor as it transitions through its critical temperature Tc. (Real-time plotting!)
Place the two Digital MultiMeters (DMM) stacked one on top of the other, and then the constant current supply on top. Plug in their power cables all to the same grounded outlets on the cart's powerstrips. Do not turn on their power yet. Place the labtop to the right of the DMMs and plug in its power cable. Set up the wooden schematic and alligator clip board in good view for the students. Set up a small styrofoam dish in front of the schematic and alligator clip board. Place the broken 4-probe apparatus in the styrofoam dish. Wrap the working 4-probe superconducting apparatus in a double layer of Aluminum foil (see video). This prevents leaking LN2 from messing up the temperature reading of the superconductor. Connect the yellow voltage probe wires (2,3) to the alligator clips labeled VOLTAGE. Connect the black power probe wires (1,4) to the alligator clips labeled CURRENT. Connect the Red and Blue Temperature probe wires to the alligator clips labeled Temperature, Red to Red and Blue to Black. Connect the USB-RS232 cables to the USB ports on the labtop and to the RS232 ports on the back of the DMMs. Connect banana cables to the front of the DMMs to the Voltage and Temperature probes on the back of the schematic board. Turn on just the DMMs. Open the laptop and Labview. Adjust settings to the DMMs or Labview if necessary (see below). Set up a camera to focus on the broken 4-probe apparatus in the shallow foam dish, and place a magnet of the surface of the superconductor. Set up the XY-Graph plot by Labview onto the projector screens.
Run the demo by hitting the start button in labview, followed by placing the Aluminum wrapped 4-probe device into a Styrofoam stand filled with LN2. Add LN2 to the shallow dish with the broken 4-probe device to demonstrate the Meissner effect in the camera view.
The DMMs used should have these settings automatically produced when turned on, if however they do not, you must use its tree based menu and adjust it to these parameters.
Address: 20, 21, or 22. Doesn't really matter, just not 31.
Settings: Baud rate; 9600: Data bits; 8: Parity; None
Open the file named "RVT Live plot". (See locations below)
Choose the correct COM Ports for the Resistance Meter and Temperature Meter.
**These parameters should be set up automatically but if they are not.**
Serial Settings: baud rate; 9600: Data bits; 8: Parity; None: Stop bits; 1.0: Flow Control; DTR/DSR: Termination Character; A: End Write on Termination Character?; True/ON: End Read on Termination Character?; True/ON: XON/XOFF Characters; XON; DC1; XOFF; DC3
Sample Frequency: 2 Hz
Controlled Current: 0.100 Amps
CONSTANT CURRENT SOURCE SETUP:
The constant current supply needs to be setup before any power is applied to the 4-probe apparatus in order to prevent burnout of the probe connections. 0.100 Amps is typically used but up to 0.400 Amps can be applied safely without damage.
DO NOT EXCEED 0.400 amps. MAX is 0.500 Amps.
With the power off, short the negative and positive terminals on the front of the constant source power supply with a really short banana cable. Turn on the power supply. Either a voltage or a current will be limiting the output. Adjust the current to 0.100 Amps and ensure that it is in current limited mode by the LED light indicator next to its dial adjustment knob. Turn off the current using the stop output button on the front of the power supply. Remove the shorting wire. Connect two banana cables to the front of the power supply and to the Current probes on the back of the schematic board. It is now okay to supply power to the 4-probe apparatus.
The working 4-Probe Superconductor apparatus are located in the dry storage cabinet inside a white carboard box. The broken ones to use for the meissner effect are located on the same shelf but in a open yellow container. The Black coated cables are the BSSCO variety (Tc = 110k) and the White coated cables are the YBCO variety (Tc = 90k). Choose the BSCCO type for a better meissner effect (actual meissner effect not simply levitation of a magnet), or the YBCO have sharper transitions to zero resistance.
The smart modem and RS-232 cables needed are located in a labeled box next to the superconductor dry storage dessicator down the thermodynamics aisle. The alligator clips and schematic board are inside this box too.
The HP Digital Multimeters are Located on the farthest back left shelf down the instrumentation aisle. You do not need their supplied cables.
The Constant Current supply power source is located on the shelf under the light sources and power strips.
Warning Sign, Cold Safety Gloves, LN2 Dewar, styrofoam cup insulating stand are located in the flame cabinet in the front entrance.
The Labview Program can be found in the shared S Drive -> Demolab -> DEMOMEDIA -> 5G50.51 - RvT -> Labview -> RvT Live Plot
A Laptop with Labview and a minimum of two USB ports is necessary. **
Run the demo by clicking on the run program button in labview. Add Aluminum wrapped 4-probe device into Styrofoam stand filled with LN2. Watch the live plot begin plotting RvT. Add LN2 to the styrofoam dish containing the non-wrapped 4-probe device with the magnet on its surface. **Do not fill too high with LN2, this will freeze the magnet to the surface preventing the meissner effect from repeling the magnet off the surface after its transition to its zero resistance state. **