srrcboy / 4-wire

4-wire (Kelvin) resistance measurement lab

4-wire

You and Your Wire

In the email I sent out I said you calculate the resistance yourself; however, this is wrong. Just use .015917Ohms as your theoretical resistance.

Program Information

• DMM1 - Address 1 (4-wire and voltage)
• DMM2 - Address 2 (current)

In the C# program you will notice a spreadsheet - this is where you should enter your data. The labels should be pretty self explanitory. It's in your best interest to copy your data in an Excel spreadsheet as well; just in case the program has an issue or if you don't plan on finishing in one sitting. Don't click on the upload button until you have all the data filled in the spreadsheet. This uploads ALL the data to the database with the correct labels and such. Also, the group ID is your groups letter assigned by West. For example, I'm group J.

Lastly, the "4-wire" button will run an automated 4-wire resistance and place the values in their cells on the spreadsheet. The "Power Supply" button will run the power supply automation and place the values where they should go. The program will detect which range you're in so you don't need to manually tell the program whether you're in a low, medium, or large current range. If you're out of range and try to run it, it'll give you an error. After you've ran the automation and collected all the manual data, copy and paste your data from your Excel spreadsheet in the correct sections on the C# spreadsheet and hit upload. This will put everything into the database with the correct labeling. This prevents idiots like Jon Covert and I from doing it wrong.

How to Measure in 4-wire Mode

To enter 4-wire mode, just hit the shift button then hit the Ohmmeter button.

Your leads should be hooked up as shown in the diagram on page 203 of the Agilent 34401A user manual. If you're confused, the HI and HI-sense are the red terminals towards the top of the DMM (HI-sense being on the left). LO and LO-sense are directly below those (LO-sense being on the left). Use the diagram to figure out how to make the measurement.

User Manual: http://cp.literature.agilent.com/litweb/pdf/34401-90004.pdf

How to Measure with 2 DMMs and Power Supply

Due to popular demand, here's an explanation on how to hook up the 2 DMMs. Imagine the wire is a resistor and you wish to measure the current and voltage of it. So, you'd place your volt meter(DMM1) across it and your ammeter(DMM2) in series with it. For example, the current can travel through the positive terminal of your power supply into the positive lead of your ammeter, out the negative lead, through the wire, and then back to the negative terminal of the power supply. Your volt meter would simply be measuring across the wire.

This is great and all but the power supplies cannot output the small and medium current stably. This means you should construct a simple resistor parallel circuit that will cut the current down. In my case I used a 1k and a 20 Ohm resistor with a voltage of 3V and current (from the power supply) of .5A. NOTE: You can get the smaller currents by setting the voltage low on the power supply. In the case of using a parallel circuit, you want to take the current from the 1k resistor (because the 20 is drawing most of the current). So, following the path of current, through the 1k resistor through the ammeter, through the wire, and back to the power supply. Once again, the volt meter is across the wire.

Before hitting the "Power Supply" button make sure your current is in range!

Database

• Server: iet2

• Username: EET321

• Password: EET321_S16

• Table: EET321_Lab4_S16

Understanding the Database

In the database you will notice there are a few items. Date/time, groupID, resistance, type, and info (optional). Under "resistance" are all the resistances; no matter what way you measured it.

Type:

• 2-wire
• 4-wire

Info:

• NP (No Pressure)
• LP (Light Pressure)
• MP (Medium Pressure)
• HP (Heavy Pressure)
• SC (Small Current)
• MC (Medium Current)
• LC (Large Current)

Licensing

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the license, or (at your option) any later version. For more information view the LICENSE file.