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Banana plugs|Simple and accurate resistance measurement with a multimeter

Banana plugs|Simple and accurate resistance measurement with a multimeter
07 Jan 2022

Measuring resistance with two wires is very convenient, but introduces measurement errors. This error can be almost eliminated by using a multimeter with 4 wires and separate source and measure terminals. Unfortunately, adding extra leads and connections increases the complexity of the measurement. You'll need to connect additional leads, and may have to replace clips and probes when going from voltage to resistance. Now, there is a new concept that enables you to make 4-wire resistance measurements with just two leads. Why use 4 wires to measure resistance? Managing two leads is challenging enough, especially when measuring small components in tight spaces. If you want to inspect small solder joints, soft connectors or chip resistors with four leads, then you have a real challenge. Switching lead configurations may require changing banana plugs, resulting in incorrect measurements. It also takes time to change from voltage probes to Kelvin leads and back again. Why use 4 wires to measure resistance? Using two wires to measure voltage has little effect on measurement accuracy. The typical input impedance of a voltage input on a multimeter is 10 megohms, so the very small current flow in the leads and the resulting drop in lead voltage are negligible. The effect of series lead resistance on the current measurement is also not significant. Unfortunately, in resistance measurements, lead resistance can cause a significant drop in accuracy. When measuring resistance, the multimeter switches the current source into the measurement loop. A current is driven through an unknown resistance and the voltage measured by the multimeter drops. If there are only two leads, as shown in Figure 1, the source current takes the same path as the measured voltage drop. The measurement lead is not a perfect conductor and has its own series resistance. By driving current through the measurement leads, you can see not only the voltage drop in the unknown resistance, but the voltage drop across each lead. Therefore, you are measuring the combined resistance of the positive lead, the unknown resistance, and the negative lead. If 4 leads are used, as shown in Figure 2, the source current measureme

Precautions for multimeter | multimeter test lead kits

Precautions for multimeter | multimeter test lead kits
24 Dec 2021

Here I introduce the precautions for using the multimeter: Take the pointer table mf47 as an example, other pointer tables are similar. 1 First of all, you need to know what you want to measure. Select the switch knob to the corresponding position as shown in the figure below. 2 When selecting the range, if you don’t know the voltage or current to be measured, you need to use a long range and then decrease in sequence (it is best to rotate the pointer of the pointer meter to the middle position of the meter head for the most accurate reading) 3 Do not change the range with power when measuring current and voltage 4 When measuring the current, observe the direction of current from + to -. The red test lead enters the black test lead out. Please do not connect it in parallel with the load or it will burn the meter easily. 5 When measuring resistance, it is not possible to perform live measurement, because the internal battery powers the meter head to drive the pointer to rotate when measuring resistance. If a live measurement is equivalent to using external electricity to supply power to the meter head, it is easy to burn the meter head. 5 When measuring the resistance of the pointer meter, you should first connect the test leads to the manual zero adjustment, and reset the zero when changing the range (the digital meter is not used) 6 When using a digital meter, if the measured reading only displays 1 at the highest digit, and the others are not displayed as over-range, the higher range should be used to decrease sequentially.] multimeter test lead kits