Ohmmeter is one type of electrical measuring tools used to measure an electrical resistance in an object or an electrical circuit. This tool consists of an analog or digital screen, depending on each type, which is equipped with a needle to show the results of the measurement scale.
The function of the ohmmeter is to measure the amount of electrical resistance that occurs in an object or circuit which will be used as power by the ohmmeter itself. The power will resist the flow of electricity that flows in a conductor.
In addition, the ohmmeter also serves to locate the fault in an electrical circuit. By detecting through other components such as cables, switches, fuses and others.
The way an ohmmeter works is quite simple, which is by generating a current flow from within this tool. Ohmmeter will measure the resistance that occurs between the two objects measured by this tool. The end of the cable is red for the positive pole and black for the negative pole.
When current flows from a component or circuit, the ohmmeter will begin to measure the voltage drop that occurs while measuring the resistance value.
There are two types of ohmmeters, namely:
1. Analog Ohmmeter
In analog ohmmeter calculation model is more manual and simpler. There is a needle that will show the number of the measurement results. To read it, you need to see which scale is designated according to the selected switch.
2. Digital Ohmmeter
Digital ohmmeters have a scale in digital form. Of course, the measurement results shown will be more detailed and accurate. You can also read the results immediately. However, there is a drawback that it is difficult to check the unstable current voltage.
Ohmmeter has several parts, here are the parts of an ohmmeter:
1. Mechanical Adjustment Screw
Mechanical adjustment screw is a screw that serves to adjust the pointer in the scale. Before using an ohmmeter, usually the pointer needs to be calibrated first so that the measurement is precise and accurate.
In addition, there are several other functions of calibration, namely:
- Maintain the condition of measuring instruments and materials being measured in accordance with their specifications.
- Determine the deviation that occurs from each measuring instrument.
- Keep measuring instruments accurate when measurements are made.
- Minimize errors that can occur due to deviation of the measuring instrument needle.
Here’s how to calibrate the ohmmeter:
- Pay attention to the Measuring Limit on the ohmmeter scale
- Connect the two ohmmeter probes, then the needle will go to number 0 or close to number 0
- Turn the mechanical adjustment screw using a min screwdriver until the needle is exactly at 0
Calibration must be done every time the range selection switch is moved. This is because the resistance in each measuring instrument is different when the range switch is moved.
2. Scale
Scale is a scale indicated by an ohmmeter. There are two types of scales, analog and digital. Scale shows the resistance that has been measured by an ohmmeter with several quantities indicated by the pointer.
For analog type ohmmeters you need to be observant to see where the needle is. Adjust also with the selected switch. As for digital ohmmeters, the numbers displayed are definite and also more detailed.
3. Pointers
The pointer is a scale pointer. This needle will move according to the amount of resistance that enters the ohmmeter. This pointer, of course, is only available in analog ohmmeters.
4. Zero Ohms Adjustment Knob
Zero ohms’ adjustment knob is a button that functions to adjust the meter needle so that it is at 0. When you press this button, the pointer will be at 0, this is useful for determining whether the pointer in the ohmmeter is still good or not.
5. Selection Switch
Selection switch is a switch that serves to determine the measurement scale.
6. Positive Probe
The positive probe is the handle of the ohmmeter and the cable that serves to connect the positive pole of the ohmmeter with the positive pole of the measuring object. This probe has a red handle and wire.
7. Negative Probe
Similar to the positive probe, the negative probe is also the handle of the ohmmeter and the cable that serves to connect the negative pole of the ohmmeter with the positive pole of the measuring object. This probe has a black handle and wire.
Some of the parts above are common parts contained in an ohmmeter. The more expensive and sophisticated ohmmeters certainly have some additional features.
Because the ohmmeter is an important type of measuring instrument that is often used, it is necessary to carry out maintenance. You need to do the following things so that the ohmmeter remains durable and can be used anytime.
- Do not use an ohmmeter while a large amount of electricity is still flowing.
- Calibrate first before taking measurements, especially after changing the selector switch on the ohmmeter.
- Keep away from objects that can damage the ohmmeter components such as sharp objects and magnets.
- Store in a safe and dry place.
- Turn off the ohmmeter when it is not in use.