A digital multimeter is important in every garage and business. Because with this tool you can easily determine various measured quantities in one. Whether current, voltage, resistance or frequencies need to be measured, the multimeter can determine all of this. You can also easily check the functionality of transistors and diodes.
Depending on the application, you should pay attention to the safety standards of the devices. When buying, it is important to pay attention to the rated voltage and overvoltage category.
The most important facts in brief
- Multimeters can measure a number of parameters. Most meters are capable of measuring voltages, currents, and resistances.
- The types of multimeters are divided into handheld multimeters, bench multimeters, current clamp meters, and USB multimeters.
- To perform a measurement with a multimeter, first, the test leads are plugged in, then the measuring range is selected and finally, a connection is made with the measuring probes and the object to be measured.
What types of multimeters are there and which one is right for you?
In general, there are four different types of multimeters:
- Handheld multimeters.
- Desktop multimeter.
- Current clamp multimeter.
- USB multimeter.
Each of these types is better suited for a different field of application and thus has its own advantages and disadvantages in use.
Depending on the meter, the models have different functions, so you should be aware of what you want to measure with it before you buy. Each multimeter can at least measure voltage (volts), current (amps), and resistance (ohms).
In addition to these basic functions, there are other functions that depend on the model. The USB multimeter is an exception here, it cannot measure resistance.
Digital handheld multimeter
The handheld digital multimeter is part of the standard equipment in the household and in the professional field, because it can be used flexibly and, depending on the model, can determine many measured variables.
- In the house: checking the wiring, sockets, appliances.
- In motor vehicles (car/motorcycle): Checking the battery, alternator.
- Checking electrical circuits, radios, electronic components.
- Checking batteries, diodes, or transistors.
- Due to its compact design, it not only fits perfectly in the hand but is also easy to take along. In addition, it is particularly suitable for beginners because of the good operability and the large selection of entry-level models. A handheld digital multimeter is an absolute must in every toolbox.
- Battery / rechargeable battery necessary.
- No batteries/accumulator.
- Accurate measurements.
- Large display.
- Versatile in use.
- It has the shape of a pen and is primarily suitable for service due to its one-hand operation.
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Digital Clamp Meter
The special feature of the current clamp is that it measures currents without first having to disconnect the conductors. In addition, it can be used while a device is in operation.
- Measurement of leads in control cabinets.
- Measurement of conductors between devices.
- Detection of interference and leakage currents.
The design of a clamp multimeter differs from a conventional multimeter mainly in the measuring method. The currents are measured inductively by surrounding the conductor with a magnetic field.
- A battery/accumulator is necessary.
- No additional connections.
- No batteries/accumulator.
- Fast diagnosis of USB devices.
- Easy to transport.
- Very handy.
If you already have a good multimeter, there is the option to use a current clamp adapter on certain models.
A digital or analog handheld multimeter cannot be used with USB devices. That’s why there are USB multimeters, which are especially useful for quickly checking devices with USB jacks or USB plugs for faults.
Basically, this meter has a USB input and a USB output. The display then shows the incoming or flowing voltage (volts) and current (amps).
- Measure the capacity and power of a power bank.
- Check the USB port of a PC or notebook for function.
- Check the power of the battery of the smartphone/tablet.
- Checking an external hard disk for a defect.
- This meter has a very compact design, so you can easily take it anywhere. It is also especially suitable for beginners due to its ease of use.
- Measures only via USB.
- Not very accurate.
- No additional connections.
The USB multimeter is a cheap option for testing the function of all devices with a USB connection. However, you should not expect high accuracy with it.
The following factors are particularly important for a multimeter:
- Type of multimeter.
- Type of measurement (average /TRMS).
- Measurement category.
- Display (digital/analog).
- Display (Counts).
- Range selection (Manual / Auto-range).
- Measured quantity / Measuring range.
- Basic accuracy.
- Comfort functions.
Type of multimeter
The very first thing you should know is what type of meter you need for your project. Each type has its own advantages and disadvantages that you should be aware of. These make the multimeter more suitable for some applications than others. We have already described the different types in more detail above, whether handheld multimeter, bench multimeter, current clamp or USB multimeter.
To make your decision easier, we have summarized the most important information in the following paragraphs.
- Digital Hand multimeter
The handheld multimeter is the most popular type because it is very versatile and handy. This meter is used by both hobbyists and professionals.
- Digital Clamp Meter
A current clamp, also called a clamp multimeter, has a special design that allows the clamp to measure currents without first disconnecting conductors. It can therefore be easily used even during the operation of a device.
- USB multimeter
The USB multimeter is a special form of a multimeter. It can only be used with USB devices, i.e. devices with a USB socket or a USB plug. In this field of application, a normal handheld multimeter cannot be used.
This meter measures the incoming or flowing voltage and current and is therefore very practical, for example, to test USB ports for their function. Furthermore, it is easy to check the battery of a cell phone, for example.
Measurement type (mean value / TRMS)
The measurement type specifies the process by which the multimeter determines a measured variable. This process influences the accuracy of the device. There are basically two different types of measurement techniques: the mean value and True RMS (TRMS), where TRMS provides more accurate results.
- RMS (mean value) = “root mean square.
- TRMS = “true root mean square.
TRMS devices have in contrast to the devices which calculate the mean value of an additional chip built-in and are therefore more expensive. This enables accurate measurement of non-sinusoidal AC voltage.
- Measurement category
In order to increase safety, multimeters are divided into four measurement categories from CAT I to CAT IV according to their range of application. It should be noted that devices that are approved in a higher category can also be used for the ranges of lower categories.
- Display (Digital/Analog)
The display can be either analog or digital. Analog devices display the measured values with a pointer, whereas a digital display uses a display with a numeric display. Both visualize values, but in a different way and thus have certain advantages and disadvantages.
Analog measuring instruments have already been largely replaced by digital ones. They are used almost only in research and education. Their biggest advantage is that they can easily detect trends or fluctuations. Furthermore, they only require batteries for resistance measurements.
However, the analog display also has some disadvantages, which is why digital devices are very popular nowadays. Among the disadvantages are that only manual range selection is possible, the devices have a lower measurement accuracy, and it is easier to make reading errors.
In addition, it should be mentioned that a sensitive mechanism is installed, which becomes defective more quickly than a numerical display.
- Display (Counts)
Counts indicate how many digits the multimeter can show on the display. The more digits can be displayed, the more decimal places a value can have. A multimeter with 4,000 counts can display the range 0 – 3,999. This means that the greater the number of counts, the better or more accurate the display.
- Range selection (Manual/Auto-range)
With inexpensive devices, the measuring range must be set manually before use. Better multimeters offer a function where the range selection happens automatically: “auto-range”.
If you have a device with an “auto-range” function, you only have to set the measured quantity. This facilitates the operation enormously and is recommended for beginners or if you do not know the measuring range exactly.
This reduces the risk of making wrong settings and prevents a possible defect of your device. The automatic range selection function can be considered as a convenience function because it does not let your multimeter measure more accurately than with a manual selection.
- Measured quantity/Measuring range
The measuring ranges in the technical data of a multimeter indicate what the respective minimum and maximum value of a measurand can be. Values above or below this range cannot be determined by the measuring instrument.
An exact measuring range is specified for each measurand. Again, it is important that you know what you want to measure with the multimeter and the approximate range of these values before you buy it.
- A multimeter makes measuring errors. How large these are, is indicated with the value of the basic accuracy.
- This value is given in percent and should be as low as possible. This allows you to compare different multimeters relatively easily.
- The basic accuracy can be read in the datasheet of a multimeter.
Comfort functions do not influence the measuring accuracy or which measured quantities you can determine with your multimeter in any way, but they can make it easier for you to use and optimize work processes. That is why they are such an important purchase criterion that you should consider.
A multimeter can have the following comfort functions or extras:
- Display illumination.
- Auto power off.
- Storage bag.
- HOLD function.
- Illuminated connection sockets.
- Mishandling lock.
- Display illumination.
- If you work at night or outdoors, then you should consider choosing a device with a backlight when making your purchase decision.