What is an Ohm Meter?
An ohmmeter is a specific type of electronic equipment that is primarily used to determine the electrical resistance of a circuit. The ohm is the unit of resistance. Calculating an object's electrical resistance involves determining how much resistance it has to current flow. Micro, mega, and milli-ohmmeters are a few examples of the several types of meters that are available, each with a distinct sensitivity level. The micro-ohmmeter is utilized in bonding contact applications because it can calculate extremely low resistances with great precision at particular test currents.
It is an electronic device that is used to measure electrical characteristics and parameters and it is of two general types:
Working in the second type is easier and more accurate considering that most operations of measuring and changing the range are automatic.
The quantities measured by the ohmmeter are generally as follows:
- Direct current DC and alternating AC amperes
- Voltage direct current DC and alternating AC
- Interruption and continuity of circuit
There are three main measuring methods, which we’re going to dive into:
The DC Direct Current Ampere Measurement Method
To be more explicit, an example of this method is the output current of the rectifier or the consumption current of the center.
This mode is used to measure the current passing through a circuit. In this case, the rotary selector switch of the ohmmeter is placed on the DCA-10 symbol, and the wires of the ohmmeter are placed in series in the circuit, the connection point of the ohmmeter wires on the ohmmeter inputs (COM) and (+10A). Make sure that the ohmmeter is connected in series in the circuit and that the passing amperage is not more than ten amperes. If it is connected in parallel with the ohmmeter circuit, it will be damaged.
The Method of Measuring AC Alternating Current Amperes
To give an example for this method, I could mention the city electricity. This mode is used to measure the current passing through an alternating current circuit such as the power supply path of the rectifier. In this mode, the rotary selector switch of the ohmmeter is placed on the AC A 10 symbol, and the ohmmeter wires are placed in series in the circuit where the wires are connected. The ohmmeter is on the ohmmeter of the (COM) and (+10A) inputs. Make sure that the ohmmeter is connected in series in the circuit and that the passing amperage is not more than ten amperes. If it is connected in parallel with the ohmmeter circuit, it will be damaged.
The Method of Measuring DC Direct Current Voltage
We can name the output voltage of the rectifier or the voltage of the center batteries as DC direct current voltage.
This mode is used to measure the voltage of a circuit such as rectifiers or batteries. Ohm meters usually have different ranges to choose from. In this case, the rotary selector switch of the ohmmeter is placed on the DC V-signal, on a higher range than the measured circuit voltage, and the wires of the ohmmeter are placed in parallel in the circuit, that is, they are connected to both ends of the device or battery to be measured.
The connection point of the ohmmeter wires on the ohmmeter is the (COM) and (mAΩV) inputs if the number one is shown. It indicates that the selected range is lower than the voltage value and a higher range should be selected and the selector key should be set to the upper range.
Working Principle of Ohmmeters
Ohmmeters operate on the principle that they have a needle and two test leads. The battery current can be used to control the needle deflection. To begin with, the meter's two test leads can be connected in series to determine an electrical circuit's resistance. Once the meter's two leads are shorted, it can be adjusted for the proper response within a predetermined range. The current in the meter will be at its highest when the needle reaches the highest point on the scale. Below is a circuit diagram for an ohmmeter.
The test leads of the meter must be disconnected after the circuit has been tested. The battery is depleted as soon as the two test leads of the meter are connected to the circuit. The rheostat will be changed when the test leads short. The resistance between the two test leads will be zero once the meter needle has been moved to its lowest, 0 positions.
Varieties of Ohmmeter
Based on its intended use, this meter can be divided into three categories: series-type ohmmeters, shunt-type ohmmeters, and multi-range type ohmmeters. Below is a succinct discussion of meters.
The component we want to measure can be connected to the ohmmeter in series when using a series-type ohmmeter. Through the parallel-connected shunt resistor R2, which uses D'Arsonval movement, the resistance value can be calculated. Both the battery and the R1 resistance can be connected in series with the R2 resistance. The two terminals A and B are used to connect the measuring component in series.
A shunt ohmmeter can be connected when the computational component is connected in parallel with the battery. This type of circuit is used to calculate low-value resistors. The following circuit can be assembled with the measuring instrument, battery, and measurement parts. Measurement components can be connected via terminals A and B.
The range of the multi-range ohmmeter is very high, this meter includes an adjuster that allows you to select the range of the meter according to your needs.
The Uses of an Ohmmeter
The ohmmeter can be used for the following things.
- This meter can be used to check the circuit's continuity, which means the circuit will become disconnected if there is an excessive or sufficient current flow.
- To test the electronic components, these are widely used in engineering electronic labs.
- These are used for debugging small ICs like PCBs and other things that need to be done in delicate devices.