Here is a DIY resistance decade tool for testing and calibration. Because it can substitute into a circuit with all standard value. This ideal is cheapest that use resistors and wires only.

In each experiment, a resistor needs to involve at all times, and Often unable to find the required resistance. This problem will solve with “DIY Cheap Resistance Decade Circuit”.

How it works

This variable resistor is not “the normal potentiometer”. It is a very high accuracy, and tolerate low current. We need a “decade resistor” in the image below. It can be selected resistive good, honest, and reliable.

Figure 1: Extech 380400 Resistance Decade Box

The way it works is very simple, is organized as a series resistor. The first set resistors have four resistors include with 1, 2, 3 and 6 ohms. The set 2 and 3 to series will add value up 10 times and 100 times is 10, 20, 30, 60, 100, 200, 300, 600 in sequence. As shown in Figure 2

How to application

For example, resistance is 39 ohms. Use a copper alligator clips to connected the resistors 3, 6 and 30 ohms in series as Figure 2. And If you Require the resistances as a decimal fraction. Such as the 5.2 ohms. But we have a 2.2 ohms resistors. Just connects in series with the 3 ohms resistors only.

The advantages of this decade resistors are cheap. Select the desired setting is simple and accurate. Without using the meter to adjust the resistance. Tolerate high current (Depending on power tolerate rate that you’re using). The disadvantage is that the Wasted space If the installation is not good, it makes the resistor shorted together.