Required Materials

1. Photon
2. Breadboard
3. Multimeter
4. Minigrabber/banana plug cables for your multimeter
5. AD623 amplifier chip
6. 670 or 680 ohm resistor
7. Dial thermometer
8. Thermocouple Type T wire
9. Sharp knife
10. Wires
11. Container for boiling water
12. Container for ice water
13. Ice

Worksheet

You can find the worksheet here.

Procedure

Preliminary Setup

1. Fill your ice container with ice and water. This will serve as the ice bath for the experiment
2. Fill the 500mL Beaker to about 250mL
3. Start the process of boiling the water using your hot plate

Thermocouple Type T Wire Setup

(You should skip this setup since we have made the thermocouples for you in this lab, BUT PLEASE READ THROUGH IT SO YOU UNDERSTAND HOW THIS WAS DONE)

1. Take a sharp knife and cut down the middle of about 1 inch of brown wire shielding on the thermocouple wire. Do this for both ends. There might be a small groove that runs down the center of the thermocouple wire and this can help you guide the knife when you make your cut.

4. Make a note of which side you want to use for your active junction and which side you want to use for your cold junction. Maybe wrap a piece of tape around the brown shielding at one end of the wire to designate one of the junctions.

5. Remove about 2-3 inches of the brown shielding near the middle of your thermocouple wire. One way this can be done is to use your knife and cut around the perimeter of the brown shielding at either end of the portion of wire that you want to remove the brown shielding from. Next, take your knife and cut down the middle of the brown shielding in between the two cuts you just made previously. Now, the brown shielding can be removed.

6. Cut the blue wire in half and strip the blue shielding from both ends of the wire that was just cut. Your modified thermocouple wire is now ready to be used in this lab's circuit.

Circuit Setup

1. Insert the AD623 onto the breadboard. Make sure the AD623 straddles the central channel on your breadboard (all pins need to be isolated from one another)
2. Turn on the bipolar power supply on the bench and set the ground for each side. Set one side to output +5V and one side to output -5V.
3. Use the following circuit drawing (Figure 4) and pin-out diagram (Figure 5) to build the circuit. Connect the +5V power supply to pin 7 and the -5V power supply to pin 4 on the AD623 instrumentation amplifier. Be aware that pin 1 corresponds to the corner of the chip that has the small circular indent (Figure 6). Take note that pins 3 and 5 are connected to ground. Remember, you can always double check your resistor's value using the resistance measurement settings on your multimeter. You want to ensure that you have the correct value as that will effect the gain of your circuit. Record that value. Do not worry about making any connections to your thermocouple wire. Those will be handled in a future step.

5. Select both blue wires that were cut from the middle of the thermocouple wire. The exposed blue wire that is closest to the active junction will be plugged into the active junction pin of the AD623 (pin 3) and the exposed blue wire that is closest to the cold junction will be plugged into the cold junction pin of the AD623 (pin 2). The blue wire may be pretty thin and you may have trouble connecting it to your breadboard. You can try using your mini grabber cables and some wires to ensure a secure connection.
6. Connect the free wires that were connected to ground and the output pin of the AD623 (pin 6) to the appropriate connections on the multimeter. Your circuit for the multimeter measurements is complete. You can use Figure 8 as a reference.

Taking Temperature Measurements

1. At this point you will want to have your ice bath and boiled water ready. Place the cold junction inside the ice bath and have the active junction free.

2. Plug in your Photon and turn on your multimeter to the 20V setting. At this point, there should be a reading on your multimeter. This value should be around 0.13V. Record the voltage. If the voltages are slightly off, double check the twisted leads of the active and cold junctions. Try to get as many twists in as possible to ensure that the leads of the red and blue wires are touching
3. Try submerging your active junction in the ice bath with the cold junction. The multimeter should be reading 0V. If it does not, call your lab AI over. Record the voltage.
4. Once you have your boiling water ready, submerge the active junction in the boiling water. The voltmeter should be reading around 0.6V, but may be less if your water wasn't completely boiling. Record the voltage.

5. Take each of these voltages and divide by the gain of the circuit. The gain can be calculated using Equation 1 and the resistor value. Now compare these compensated values with the values shown in the table for a type T thermocouple to get a rough idea of the temperatures that you measured and ask yourself if they make sense.

$$ V_{out} = (1 + {100k \Omega}/{R_g}) \times V_{in} $$

7. At this point you may want to have some more boiled water ready in case it has cooled off and another ice bath in case the ice has melted. You will now use the Thermocouple.m MATLAB script to run through a few experiments. You will need to write your own part of the code to save your temperature recordings. You should try and conduct tests at a few different temperatures (ice bath, room temperature, boiling water, etc.) and make sure you acquire several data points at each temperature so that you can then take an average. While taking measurements with the Photon, you will also need to simultaneously take measurements with the temperature dial, as you will be making comparisons between Photon and dial measurements . Make sure you record all the dial readings. It is also a good idea to let the active junction rest at its new temperature before taking data. Don't forget to fill out the worksheet!