Multimeter, Types, Functions, Working, Advantages & Disadvantages
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The majority of engineers and technicians in the electronics industry are familiar with the measurement tool known as a multimeter. Depending on their characteristics, multimeters come in a variety of shapes and sizes on the market. A multimeter is a crucial measurement tool that is used in every lab and engineering workshop. This device’s primary purpose is to measure the electrical characteristics of tools and industrial wiring. Multimeters are currently used for a variety of tasks depending on the situation, such as working with electricity, laboratories, power sources, and circuits. On the front of the multimeter, there are dials or rotary switches that can be used to select among the various electrical parameters. Overviews of various multimeter types are covered in this article.
What is a Multimeter?
Every electronic technician and engineer’s go-to piece of test equipment is a multimeter, which is an electronic instrument. Voltage, current, and resistance are the three fundamental electrical properties that a multimeter is primarily used to measure. In an electrical circuit, it can also be used to check the continuity between two points. This post primarily introduces the fundamentals of multimeters, including their uses and various types. Let’s look at each of these.
The multimeter can function as an ammeter, voltmeter, and ohmmeter, among other things. It is a portable device with positive and negative indicator needles above an LCD digital display with numbers. Electric motors, home wiring, batteries, and power supplies can all be tested using multimeters.
A display, a power source, probes, and controls are the multimeter’s primary components.
How to use a Multimeter?
Both analog and digital multimeters perform and operate in much the same way. This device has three ports and two leads, a red and a black probe. The red color leads are used to plug into specific ports as needed, while the black color leads are used to plug into the common port.
The instrument’s center knob can be turned ON after the leads have been plugged in to perform the proper function for the particular component test. For instance, the multimeter will detect DC voltage up to 20V once the knob is set to 20V DC. Set the knob on the multimeter to the 2V/200mV range to calculate low voltages.
You must touch the ends of each probe to the terminal ends of the components in order to get a reading from the meter. When used on devices and circuits to supply current or voltage that doesn’t exceed the meter’s highest rating, different types of multimeter devices are very safe to use.
We must be extremely careful when measuring, so avoid touching the metal bar ends of the tester when it is turned on to avoid receiving an electrical shock.
Functions of Multimeters
Depending on the model, these instruments are able to produce a variety of readings. Therefore, the most common uses for basic types of multimeters include measuring amperage, resistance, voltage, and checking for continuity. A complete circuit can also be tested as shown below.
- AC Voltage & Amperage
- DC Voltage & Amperage
- Capacity in Farads
- Resistance in Ohms
- The temperature in Fahrenheit/ Celsius
- Inductance Henrys
- Conductance in Siemens
- Frequency in Hz
- Duty Cycle
Some multimeter types allow the attachment of special sensors or accessories for additional readings such as acidity, light level, alkalinity, wind speed, and relative humidity.
Types of Multimeter
There are different types of multimeters like Analog Multimeter, Digital Multimeter and Fluke multimeter.
A moving coil meter is used in the construction of the analog multimeter, also known as the VOM (Volt-Ohm-Milliammeter), along with a pointer to show the reading on the scale. A coil that is wound around a drum and positioned between two permanent magnets makes up the moving coil meter. The magnetic field of the permanent magnets reacts with the magnetic field of the coil as current flows through it, creating a force that causes the pointer attached to the drum to deflect on the scale, indicating the current reading. In order to control the deflection of the pointer, it also consists of springs attached to the drum, which exert an opposing force on the drum’s motion.
The D Arsonval movement mentioned above can be used directly to measure DC. The current to be measured should, however, be less than the meter’s full-scale deflection current. The current divider rule is applied for higher currents. The meter can also be used to measure current in multiple ranges by using various values of shunt resistors. The instrument must be connected in series with the unidentified current source in order to measure current.
A resistor is connected in series with the meter to measure DC voltage, and the resistance of the meter is taken into account so that the current flowing through the resistor is equal to the current flowing through the meter and the total reading represents the voltage reading. The instrument and the unknown voltage source must be connected in parallel to measure voltage. Different resistors with varying values can be used for multirange measurement and connected in series with the meter.
The unknown resistance is connected in series with the meter and across a battery for the purpose of measuring resistance, making the current flowing through the meter directly proportional to the unknown resistance. The same principle is used to measure AC voltage or current, but the AC parameter to be measured is first rectified and filtered to produce the DC parameter, and the meter displays the RMS value of the AC signal. An analog multimeter has the benefits of being affordable, not requiring a battery, and being able to measure reading fluctuations. Sensitivity and accuracy are the two main elements that influence the measurement. The unit of measurement for sensitivity is ohms per volt and refers to the reciprocal of the full-scale deflection current.
A digital multimeter (DMM) is what we used most frequently. The DMM can carry out all tasks from AC to DC aside from analog. The figure shows two probes with positive and negative indications in black and red. In order to measure ohms, volts, or amperes, the user connected the red probe and the black probe to the COM JACK. Voltage, resistance, and diode testing can all be done using the COM and V jacks on the right side of the image. The two jacks are used when an LCD displays the measurement—volts, ohms, amps, etc.—that is being made. The overload protection shields the user and guards against damage to the circuit and meter.
The internal circuitry of the digital multimeter consists of a signal conditioning circuitry, an analog to digital converter, an LCD, a knob to select different ranges of the three electrical characteristics, and other components. Depending on where the knob is positioned, concentric rings on the PCB are either connected or disconnected. The section of the PCB is activated to carry out the corresponding measurement as soon as the required parameter and the range are chosen.
In order to measure resistance, current is passed through an unknown resistor from a constant current source. The voltage across the resistor is then amplified and fed to an analog to digital converter, where the output, which takes the form of resistance, is then displayed on the digital display. To measure an unknown AC voltage, the voltage is first attenuated to obtain a suitable range, rectified to DC signal, and then fed to an A/D converter as an analog DC signal to produce a display that shows the RMS value of the AC signal.
The unknown input is first transformed into a voltage signal, just like when measuring an AC or DC, and then fed into an analog to digital converter to produce the desired output (with rectification for AC signals). A digital multimeter’s output display, which shows the measured value directly, high accuracy, and capability to read both positive and negative values are its advantages.
Types of Digital Multimeter
Digital multimeters are available in three types.
The random digital multimeter can be built with a variety of teamwork features. This instrument is used to measure electrical resistance as well as voltage and typically has a large display. There are some devices that can measure humidity, duty cycle, pressure, frequency, temperature, etc. with advanced features. One of the most used and well-known instruments is the fluke multimeter.
The main purpose of this kind of multimeter is calibration, and it is used to calibrate currents, volts, and other electrical units.
The transient voltage is protected against by the fluke multimeters. It is a compact, portable instrument used to test diodes and measure voltage and current. The desired function can be selected using the multimeter’s multiple selectors. The fluke MM chooses the majority of measurements automatically. To take an accurate reading, the signal’s magnitude does not need to be known or calculated; instead, it is simply moved to the correct port for the required measurement. When connected to the incorrect port, the fuse is protected to avoid damage.
Clamp Digital Multimeter
The electricity flow is measured using a clamp digital multimeter. This multimeter, as its name implies, has a feature called clamp that measures amps whenever the probes measure volts. The reading of the voltage and the amps can be multiplied to adjust the power consumption in place of the watts. Different types of settings are an additional feature of this multimeter. While measuring, the appropriate feature is used.
This particular multimeter has fixed instruments for measuring current flow. This device significantly differs from the fluke variety because the fluke multimeter uses a clamp to measure current flow. Therefore, it is usually only advised for professionals to use this instrument.
The auto-ranging multimeter is the most expensive of all the different types of digital multimeters, but it is also the easiest to use. This multimeter has fewer positions and a knob in the middle. Therefore, it doesn’t automatically change to measure. This tool can be used in straightforward projects. This tool comes highly recommended for both amateur and home electricians. It typically only measures one component at a time.
Types of Multimeter Probes
The primary purpose of the various test probes found in a multimeter is to connect to the circuit being tested. The three most popular kinds of probes are crocodile clips, pointed probes, and retractable hook clips. A multimeter typically has two-color wires, such as black and red, that are used as leads or probes. The probe has a banana jack on one end that plugs into a multimeter and a probe tip on the other end that is used to test the circuit. In contrast to the black probe, which is used for -Ve, the red probe is used for +ve.
These probes have a probe tip on one end and banana plugs on the other. To protect them from the incredibly high current, most multimeters come with fuses. This fuse will stop the flow of current when the multimeter receives an excessive amount of current, preventing damage. Depending on whether they are measuring low current or high current, some multimeters have fuses that dictate where the probes should be placed.
The last port, designated VΩ, is used for ohms and volts. This port occasionally merges with the third, which is labeled mAVΩ after it. If there are four ports on the multimeter, the red probe can be plugged into the VΩ port to measure both resistance and voltage. The current can be calculated when the red probe is plugged into the mA port, and it can be measured in amps when it is plugged into the A port. For instance, the VΩ port on a multimeter can be used to test a transistor in addition to testing a diode.
Advantages and Disadvantages of Digital Multimeter
The advantages of a digital multimeter include the following.
- Measurement accuracy is high
- It includes auto polarity functions
- It gives an automatic o/p display.
- The measurement results of the meter can record and store in memory and synchronizes through a PC
- It ensures accuracy
- The meter reading accuracy cannot depend on the charging of the battery
- Resistance toward mechanical damage.
- Zero adjustments cannot be required
- Measuring ranges can be selected through manual or automatically
The disadvantages of digital multimeter include the following
- As compared to analog, it is expensive
- Through variations in measurement, this multimeter does not function properly. Finding one that fits your requirements exactly can be difficult.
Advantages and Disadvantages of Analog Multimeter
The advantages of an analog multimeter include the following.
- Power utilization is not required from the fixed power supply while measuring current and voltage
- Possibility of achieving measurements at below-30 ° С temperature
- By using this instrument, all measurements can be done simply.
- When high precision is not necessary, then quick operation through a large amount of measurement can be done.
- The signal level can be observed
The disadvantages of analog multimeter include the following
- These are expensive
- These meters are large
- They are susceptible to vibration or shock.
- Voltage polarity cannot be recognized
- Incorrect because of the earth’s magnetic field effect.
- The movement of the pointer is slow and it cannot be utilized to measure voltages through frequencies above 50 HZ.
- An unexpected change in the signal can notice through an analog multimeter more quickly as compared with a digital multimeter.
- Input resistance is less, thus a high error while measuring less voltage
- These are sensitive to vibration, mechanical damage.
Types of Multimeter Applications
Applications for different multimeter types include numerous electrical and electronic projects for component testing as well as use in a variety of measurement applications.
Temperature and Environmental Applications
- DMM internal temperature
- Low-cost weather station
- Peak to Peak and DC average measurement
- High and low-value DC measurement
- True RMS AC
- DC measurement
- Measuring resistance with constant voltage
- Micro ohmmeter
- Measuring resistance with constant current
Time and Frequency measurement
- Time measurement
- Fast frequency