How Do Volt Ohm Meter Work?

If it happens that you are a hobbyist who often use the VOM tool on your projects, you might come to the point asking yourself about how does this magnificent tool work? Students taking up the field of electronics will also be asked by their instructors to conduct a research about how this tool works. Thus, it is the main subject of this article that will offer you a good explanation.

The primary core of the Volt Ohm Meter or VOM is the Electrical Meter, it is a small electromagnetic coil that carries the current that are to be tested. Along with this electromagnetic coil is a permanent magnet placed at the poles. This works by restoring the force or pulling back the two spiral hair-springs at the default level.

When current is applied on the coil, movement will occur and there is a positive sign that there is a presence of electric current flow. There are four characteristics of electrical properties that you can test with your Volt Meter and they are the Voltage, Ohms, Current and Resistance. Among them that you have selected, a flow of current will always pass through the coil to provide you the output.

In reading Voltages, a group of resistors are connected in series to the coil. They vary in values allowing you to make a selection range for voltage to be measured. The same concept is applied on the current except that the resistors are connected in parallel with the coil. Finally is the Resistance or Ohms, there is no supplied source of power unlike the Voltage and Current. This makes the reason that the VOM contains a Dry Cell battery. Exactly just like the Voltage principle, a series of resistors are connected to the coil to output the value of the tested circuit.

After reading this article, you might also come into doubt or curiosity on how does a DMM or Digital Multi-Meter work?

Digital Multi-Meters works exactly the same as the analog VOM but the differences is that most parts are electronically upgraded. The primary core of the analog meter was substituted with a voltmeter. The Meter-Scale has been substituted with graphic display that will show you direct results in the form of numeric numbers. And the same goes with the other parts which makes the DMM output a more accurate measurement.

How Do You Use a Volt Ohm Meter?

The Volt Ohm Meter is more commonly known as "VOM". It is a type of tool where you can use it to gauge electrical properties such as Resistance, Voltage and Current. There is another version of this tool which is known as the Digital Multi-Meter or DMM. However, it is still preferred that you make use of the traditional VOM especially when you are a student or hobbyist starting to learn the field of electronics.

So how do you use a Volt Ohm Meter (VOM)?

Before we can learn how to use this type of tool, you need to know the parts and their functions. Below are the basic parts that you will most likely going to make some adjustments before you can begin reading values from your circuits:

Test Probe

You will have two test probes that are distinguished in their Red or Black color. The Red Probe indicates the positive terminal while the black denotes the negative terminal. It is important for you to know on the part of your circuit the location of the ground since it is where you will most likely going to connect the negative test probe. Connecting the probes in reverse polarity could damage the equipment and it will no longer produce accurate results.

Scale Meter

The Scale Meter consists of numbers and series of gradations. This will provide you a reading result with two decimal places. Reading is done by checking on the meter-pointer on the scale. The pointer should fall under a certain range of level then count the series of gradations to the exact tip of the pointer. You may then multiply that value on the value of the Selector Scale that you have selected.

Selector Scale

On the middle part of the analog meter, there is a huge rotating knob and this is the Selector Scale. This is the first part of the tool that required adjustment before use. If you are going to conduct a reading about voltage then you need to turn the knob on that scale. Beside from the Voltage (DC and AC), you can also do a reading in Amperes and Resistances.

Zero Corrector

Just below the Scale Meter, you will find there a small rounded button. This is the Zero Corrector. It is used to adjust the meter-pointer to point at the exact starting level. Adjusting it will require you to use the flat screw-driver and you should be gentle when making your adjustment.

Zero Ohms Adjust

Reading resistances will require you to adjust the Zero Ohms Adjustment knob. It is simply a small rotating knob that you can easily find on your VOM. Normally, it is located on the lower right bottom of the Meter Scale. Before reading resistances, you need to make sure that the meter-pointer is set at the exact starting level. Failure to make this adjustment will result in an inaccurate values.

Steps in using the Volt Ohm Meter:

Depending on the type of electrical properties that you need to read, you must first adjust the Zero Corrector adjustment setting. It is often adjusted by the manufacturer but there are some instances where they are not. Take note, you cannot adjust it by hand where you need to make use of a flat screw-driver.

The next step is to adjust the Selector Scale. If you wish to read Voltages then you need to rotate the knob and select the option. There are two types of voltages which are DC and AC. The DC levels are used to measure "Direct currents", voltages with polarities. The AC levels is the opposite of DC and stands for "Alternating Currents". The same procedure applies when reading Currents and Resistances.

After setting-up those necessary adjustments, you may now hold your test probes with your hands and begin testing some areas in your circuit. Good luck...

The VOM and DMM Multi-Meters

The VOM and DMM are both multi-meter devices where it functions as a valuable tool in reading electrical properties such as Resistance, Current, Voltage and etc... Electricians, Electronic Technicians, Students (taking-up related technology courses) and hobbyist makes use of this tool on their projects. Without the use of VOM and DMM, we wont be able to conduct repairs on our broken equipment or devices. We also wont be able to make those wonderful projects and etc... Moreover, there are differences between these two type of tool which is what we are going to discuss on this article.

VOM

VOM stands for "Volt Ohm Meter". It is the traditional measuring device that are commonly used by an Electronic Technician. They are using it to diagnose any broken equipment to determine the defective component for replacement. The use of this tool requires some skills in reading the scale-chart.

DMM

DMM stands for "Digital Multi-Meter". It is the same tool as the VOM but the main difference on the output is that the DMM displays the values in direct numbers. The output can also be setup to four decimal places providing you with a more accurate result. However, the output is usually unstable especially on the last four decimal places.

Both of these Multi-Meter tool consists of two test probe. One is color Red and black is the other. The red probe indicates the positive polarity while the black is for the negative polarity. It is very important that you should always be aware on the part of the circuit where you make contacts with your test probes. Take note that the analog VOM meter cannot provide you negative readings unlike the DMM. Another important to remember when using the VOM is to avoid connecting the test probe in reverse polarity because it can damage the tool.

The VOM are recommended on those simple circuits since accuracy doesn't really matter and there is a huge range of level for the required output. DMM are used on highly sophisticated circuits that needs to output accurate measurement and such equipment are the Oscilloscope, Multi-Meters and other measuring devices that generate highly precise measurement.

There are advantages and disadvantages between these two Multi-Meter devices but there is still a huge debate on which of them are the best tool to use. I guess it's all up to you to decide whether to use one of them or simply both.