Hello.
I'm currently working on a coating part, measuring resistance.
I have two questions, so I came up with a 1:1 question like this.
please answer about my question.
1. It is often said that 4 probe points are advantageous for low-resistance measurement and 2-probe points are advantageous for high-resistance measurements.
I know, but I'm curious as to why. I did a little search, but it was because of the error rate.
I know. Please explain in an easy to understand way.
2. Also, since 4 probes measure sheet resistance => R(s) = ro/t, as the sample coating thickness increases, the sheet resistance decreases
lowers. However, when measuring the current sample thickness, the sheet resistance tends to increase even if the sample thickness increases.
I'm curious as to why this is happening.
1. Suppose, for example, that you are measuring a resistance of about 0.1 ohms. However, if the lead rod cable resistance of the tester is 0.01 ohms, an error of 10% already occurs here. In the case of a general tester, the reason why the two lead rods are shorted and the resistance value is 0. In order to eliminate this error, there is no choice but to use the 4 wire probe method.
That is, a constant current flows through one side and the voltage across the resistor is measured with the other side. Since it is driven by a constant current source, the voltage generated from the voltage across the resistor becomes V = IR regardless of the cable resistance, and the input resistance of the voltmeter can ignore the cable resistance. can .
The second question is difficult to understand without seeing it in person. Obviously, sheet resistance is inversely proportional to thickness.
Make sure you don't miss any variables. There must be something else .