Multimeter - Multi-function measuring device for multifunctional measuring

Due to its versatility, the multimeter is the most important measuring device for electricians in many countries. But what exactly does a multimeter need to be able to do to fully meet your needs?

In order to provide orientation here, you will find out below:

• Which multimeters are available?
• Measurement types and ranges
• Measurement categories and meaning
• Check continuity with the multimeter
• Diode test with the multimeter
• What other functions are advantageous?
• What else characterises a good multimeter?
• Multimeter or clamp meter?
• Practical knowledge: How do you measure with a multimeter?
• Comparison of Wiha multimeters

Which multimeters are available?

Analogue multimeters

Multimeters have been around since the 1920s. Their history began in analogue form and analogue multimeters are still available on the market today. Mainly because the pointer display clearly visualises fluctuations and trends in the measured value. However, reading the analogue display can easily lead to misinterpretations. In addition, the devices are more sensitive than their successors, the digital multimeters. For these reasons, among others, the digital multimeter is the most important on the market today. The following information therefore also focuses on this type of multimeter.

Digital handheld multimeters or desktop multimeters

Most multimeters are mobile. They are compact and battery-operated. So you can carry them conveniently in your tool transport system. They are particularly practical if you frequently work at different locations. For the sake of completeness, however, it should be mentioned that there are also special multimeters for stationary use in workshops or laboratories. These are known as desktop multimeters. They normally run on mains power. The display is larger, which is why they are less compact than handheld multimeters. They also offer a very wide range of functions, which, however, exceed the actual requirements during electrical installation. A high-quality handheld multimeter covers all the necessary measurement types and ranges required for mobile use.

Measurement types and ranges

You expect a multimeter to cover as many measurements as possible. If you use your device professionally, this requirement is naturally greater than in the DIY sector. The device is in continuous use. You have to carry out measurements under a wide variety of conditions. And health and safety regulations place higher demands on your measuring device.

Even with inexpensive all-round multimeters from discount stores, you can usually measure voltage, current and resistance within certain measuring ranges. Your application possibilities are limited by the measuring range that your device can measure! This is the most important point that distinguishes one model from another. Large measuring ranges are particularly important in a professional environment. Read more about this below.

Furthermore, in addition to standard measurements, high-quality devices offer additional measurements such as frequency measurement, capacitance measurement or temperature determination.

Standard measuring functions

1. Measurement of voltage in volts

A multimeter must be able to measure the voltage in a circuit. Both under direct and alternating voltage. For home use, it is sufficient if the device measures up to 600V AC / DC. In the commercial sector, the measuring range should be as high as possible. Very good devices are designed for measurements up to 1000 V AC / DC.

To safely carry out installation work in the area of wallboxes or photovoltaic systems (single-family homes), for example, you need a device that is suitable for a measuring range of up to 1000 V DC.

2. Measurement of current in amperes

Of course, the multimeter must also be able to measure current. Also direct and alternating current. A measuring range of up to 10A AC/DC is standard on the market. In this context, you should know that a multimeter can usually measure high currents for a maximum of 30 seconds without any problems. A longer measurement will damage the multimeter.

Both inexpensive and high-priced devices cover lower measuring ranges in the mA (milliampere) range. However, if you want to measure even smaller currents in the µA (micro-ampere) range, you will need a higher-quality device. Such small measured variables are of particular interest to you if you work in the HVAC sector. During the maintenance of gas systems, it is necessary to measure ionisation currents. This is only possible if your multimeter can measure in the micro-ampere range between 3 and 7 µA DC.

3. Measurement of resistance in ohms

Determining the resistance is another measurement that you can make with any multimeter. In the multimeter, the measurement is determined indirectly using Ohm's law. Even entry-level multimeters are able to do this. It is therefore no challenge for most devices to determine how much voltage is required to conduct current through switches, cables or fuses. Or to check these components for defects.

If you want to measure very large resistances, pay attention to the limitation of the measuring range at the upper end of the scale. If the multimeter can measure MOhms, it is easy to check insulation resistances in fire protection or when testing the insulation on electrical systems, for example.

A measuring device with a high resistance measuring range is also required for testing photovoltaic modules. With 200 MΩ, for example, you are well equipped for this area

Additional measuring functions in high-end multimeters

1. Measurement of frequency in Hertz

If you frequently work with alternating voltage and alternating current, it makes sense to buy a multimeter that offers the option of measuring the frequency. If, for example, an AC motor is running at a different frequency than usual, this can be determined with your multifunctional measuring device. A large measuring range also sets the tone here.

2. Measurement of capacitance in farads

The measurement of the capacitance of a capacitor in a single-phase motor, for example, can be determined using a multimeter that measures farads. You need such a device if you work in supply engineering and maintain heating, ventilation, air conditioning and refrigeration systems.

3. Measurement of temperature in C°

High-quality appliances also offer the option of determining the temperature. A temperature sensor is supplied for this purpose.

Measurement categories and meaning

In addition to the measuring range, the measuring category plays a major role in device selection. They are also relevant for all electrical measuring and testing devices. The term "safety levels" is also often used. However, it means the same thing.

The measurement category indicates the area of application in the low-voltage network for which the electrical measuring and testing device is suitable. There are four categories from CAT I to CAT IV. In addition to the area of application, the maximum voltage for which the device is authorised is also specified. This is divided into three ranges:

• Up to 300V
• Up to 600V
• Up to 1000V

The measuring category / safety level of the device therefore briefly summarises the following information: For which application and under which maximum voltage the device may be used.

The measurement categories ensure safety during the measurement. Especially for you as the user. Failure to observe them exposes you to an increased risk of electric shock, electric arcs, fire or explosion, which can occur in the event of overvoltage.

The following diagram clearly visualises the scope of application of the four measurement categories in the low-voltage range:

Continuity test with the multimeter

One of the most important measurements in electrical circuits is the continuity test. Before commissioning an electrical system, this test is even prescribed by DIN VDE standard 0100-600.

The continuity test can be used to determine, for example:

• Whether a fuse has blown
• Whether there are short-circuited conductors
• Whether there are other interruptions in the circuit, e.g. because a solder joint is broken

During the test, the test device sends a small test current through the circuit to determine whether it is closed or open, i.e. continuous.

You can check the continuity quickly and efficiently using a multimeter, for example. Even the inexpensive DIY models offer this function. Higher-quality devices also offer an acoustic, loud signal that sounds without delay when the circuit has continuity. This means you do not have to read the result on the display and can concentrate fully on the measurement itself. There are also special devices on the market that only test for continuity. 

You can find all the information you need on the continuity tester category page.

To the Continuity tester

Diode test with the multimeter

In addition to the continuity test, the diode test is another important measurement that is frequently used in the everyday work of electricians. Diodes block the flow of current in one direction and allow it to pass in the other. The diode therefore has the task of conducting the current in one direction only. Diodes are used in almost all electronic devices. You can therefore detect defective diodes with a multimeter that also offers a diode test function.

What other functions are advantageous?

Autorange function

High-quality multimeters are equipped with automatic measuring range selection (autorange). With such devices, the multimeter automatically selects the measuring range. You as the user only have to set the measurement type. Your test device takes care of everything else. On the one hand, this is convenient. On the other hand, the function ensures accurate measurement results.

Note:

If the device does not have an autorange function: If you cannot estimate the measuring range with certainty, start your measurement with the highest possible measuring range. Then gradually reduce the range. This will ensure that you do not damage your measuring device because you have selected an unsuitable measuring range.

TRUE-RMS - effective value measurement

If multimeters have a TRUE-RMS function, the device measures more accurately if the sinusoidal shape of an AC voltage deviates from the ideal, i.e. if it is distorted, not typically sinusoidal or disturbed. The measurement results are therefore more meaningful and correct than with devices that only use an RMS function. The TRUE-RMS function is also abbreviated to TRMS. It is particularly important for all specialists in industrial electrics. You do not need this function for home use.

Data hold function

The data hold function saves measured values on the device. This is particularly useful if the measured value cannot be read directly because you are measuring in confined spaces. You can also often compare the saved values with other measured values.

Non-contact voltage measurement

Voltage can be determined quickly and easily without contact using multimeters with this function. This has the advantage that the test lead tips do not have to be inserted into the circuit. For example, you can detect live wires in the walls before drilling. Only a few multimeters currently offer this convenience. It is only used as an initial indication of the absence of voltage and does not replace the prescribed all-pole check with a two-pole voltage tester.

What else characterises a high-quality multimeter?

Fuses

Cheap appliances often only have a glass tube fuse installed. If the currents you measure are too high, this can be life-threatening. High-quality appliances are fitted with two fuses that blow if the currents are too high, thus interrupting the circuit.

Robustness

As mentioned at the beginning, multimeters are used more frequently in a professional environment. The more frequently the device is used, the more value you should place on its robustness. So look out for sturdy rotary switches, a high-quality rubber sheath and replaceable test leads with protective caps.

Display stand

Both hands are usually required for the measurement itself because the measuring probes have to be integrated into the circuit. A device with a stand is therefore practical. This makes it easier to read the measured values and reach the operating buttons.

Illuminated, large LCD display

If you often work in poor lighting conditions, illuminated displays are an important purchase criterion. LCD displays are also easier to read. You should also pay attention to the size of the display itself in terms of legibility.

Multimeter or clamp meter?

Like many other users, you may be asking yourself whether a clamp meter with multifunctional measuring options is a sensible alternative to a multimeter. The clamp meters available on the market today offer many comparable functions. They also have the advantage that measurements can be taken without breaking the measuring circuit. However, the indirect measurement technology of clamp meters also means that very small currents in the microampere or milliampere range provide less accurate measurement results. The cheaper the device, the less precise. So if you need a multifunctional measuring device for these small measuring ranges, you are better off with a multimeter.

When troubleshooting electrical systems, it is often necessary to determine current and voltage SIMULTANEOUSLY. However, unless you have a device with several channels, this is not possible. It is therefore worth supplementing the multimeter with a handy clamp meter for professional use. As mentioned at the beginning, this is also known as a clamp multimeter.

You can find detailed information on the clamp meter category page.

To the clamp meter

Practical knowledge: How do you measure with a multimeter?

Multimeters always have the same design and consist of three main components. They are very similar to operate:

Operating switch with measured variable selection

The rotary switch is the centrepiece of every multimeter. You use it to set the respective measurement type. The switches on autorange models are clearer, as there is no need to select the measuring range

Connections for the test leads

There are usually three connection sockets for the test leads. Very inexpensive devices only offer two connections. High-end devices sometimes have four, because they measure the amperage completely separately from other measured variables.

Test leads

Two measuring leads, in black and red, are connected to the matching coloured socket on the measuring device. The measuring tips are then integrated into the measuring circuit.

 You can find more information on measuring with the multimeter on our knowledge page:

 To the knowledge page Electrical Measuring Devices

Comparison of Wiha multimeters

Wiha offers two high-quality and precise multimeters. Both have large measuring ranges. One version is particularly versatile because it can also measure extremely low currents and very high voltages, for example. It is therefore particularly suitable for industrial applications. The following table clearly summarises all the features: