In addition to the oscilloscope, a digital multimeter (DMM) is one of the most important measuring and diagnostic tools in electronics and electrical engineering. It has a permanent place in the tool box of engineers, technicians, electricians, maintenance, repair and overhaul (MRO) departments, and IoT developers. If voltage, current or resistance needs to be measured or power/signal lines checked for continuity – a DMM provides users with the necessary electronic and electric circuit readings. The following article explains which aspects should be considered when choosing a DMM.
Applications
Depending on the model, digital multimeters are suitable for measurements in various applications. These include industrial, automotive, consumer electronics, communications, computer technology and the Internet of Things (IoT).
Before buying a DMM, users should know exactly when they want to use the device and how they can make use of the devices’ features. Depending on the area of application and measurement tasks, stationary benchtop and system multimeters or portable/handheld devices are possible solutions, such as the 100, 200, 400 and 800 Voltcraft series from Conrad Business Supplies.
Designing the Voltcraft series focused on a convenient, robust design and easy handling. From the entry-level models all the way up to models for professional measurement use, the Voltcraft series covers virtually all user requirements.
Knowing all CAT classes
When choosing the ideal DMM, it is helpful to know the different CAT classes. Depending on the application field, digital multimeters are subdivided into different measurement categories using CAT classes. Conrad Business Supplies offers devices for the following safety classes according to EN61010:
- CAT I devices: for measurements on devices that are either battery-operated or have a built-in transformer for galvanic isolation, for example repairing flashlights, transistor radios, stereos, conventional 12/24V automotive board electronics, etc.
- CAT II devices: for measurements on devices connected to the mains by a mains plug, for example household appliances or power tools.
- CAT III devices: for measurements in the domestic installation area and for permanently installed devices, for example sub-distributions and sockets.
- CAT IV devices: for measurements at the source of low-voltage installations and outdoor equipment, for example: measurements on main fuses, photovoltaic systems, motor vehicles with electric drives.
DMM basic functions
The 100, 200, 400, and 800 Voltcraft series of portable DMMs feature basic functions such as measuring voltage, current, and resistance in both DC and AC current/voltage environments.
Continuity testing is an additional function offered by some models. The continuity test is used to determine if two points are electrically connected. The DMM gives the user an audible signal to indicate continuity.
The diode test function indicates whether a diode works or not and selected models have an additional capacitance measurement function.
Advanced Voltcraft DMMs are equipped with even more features and measurement capabilities, for example, frequency and inductance. Measuring temperature, 3-phase rotation or duty cycle are also possible.
Entry-level VC 100 series
For all domestic and hobby measuring tasks, from entry-level up to CAT III 600V professional tasks – the entry-level VC 100 series with six models is design with these applications in mind. Depending on the requirements, devices with manual or automatic range selection (auto-range) are available. The auto-range function selects the best possible measurement range during a measurement providing the best resolution. Users can focus on the concise measurement making handling much easier.
VC 200 series sets safety standards
Safety standards are set by Conrad Business Supplies’ VC 200 series with five models optimised for training and education. Many of the features make the devices ideal for both hobbyists and professionals. Power consumption is reduced so that operating times of up to 6000h can be achieved with one battery. All models of the VC 200 series are equipped with an impedance switch. This allows a short-term reduction of the input resistance from 10MΩ to 400kΩ with the touch of a button in order to avoid incorrect stray voltage measurements.
As a special feature, all devices of the VC 200 series have a self-resetting 400mA fuse. Exceeding the current measuring range limits the measuring current and prevents blowing the conventionally-integrated fuse. In the education and training area, it is quite possible that the measuring range is estimated wrongly or that the connection was not carried out correctly. This would have necessitated replacing the triggered fuse incurring additional time and associated costs.
Also, the correct measuring jack assignment is shown on the display of all models depending on the type of measurement.
Counts explained
Depending on the model, the VC 200 series devices offer a display range of 2000 to 6000 counts. But what exactly does the term “counts” mean? It indicates the largest possible displayable characters on the display (0 included, it means 6000 counts = usual display range 0 to 5999). The larger the count, the better the display value resolution. Likewise, the measuring range goes further without switching to the next higher or lower measuring range. For example: 2000 vs 4000 counts. Measurement of 230.3V -> display with 2000 counts = 230V, display with 4000 counts = 230.3V.
VC-400 E – robust and IP65 protection
Three models are part of the extremely robust VC-400 E multimeter series, which is ideally suited for use in trade and industry. The IP65 dustproof and waterproof devices withstand a fall from a height of 2m. All models are rubberized and have many features that make the devices particularly attractive for electricians, fitters and service technicians.
VC 800 for professionals
The VC 800 professional series with five models is ideal for research and development use and covers all challenges. Robust and reliable, professional functionality, ergonomic shape and safety are the attributes that describe these professional DMMs. When it comes to safety, there is no better product than the VC 800 series.
Thanks to its special housing construction, the housing can only be opened for battery and fuse replacement if the device has been disconnected from all test leads. The integrated TLD function (Test-Lead-Detection) warns users of incorrectly connected test leads. For input voltages greater than 30V, a warning icon appears on the display. The VC 800 series is also equipped with an optical interface.
Measure asymmetrical voltages and currents with TrueRMS
Depending on the application, the DMM of choice should also allow true rms measurements (TrueRMS). This function measures unbalanced voltages and currents that deviate from the basic form of the sine wave. Such unbalanced voltages usually occur in power regulators such as dimmers, speed controllers, clocked switching regulators, pulsed chargers or electronic speed controllers in model making, etc.
Conventional average value measuring devices sometimes show very large measuring deviations in such special measuring tasks. Real rms measurements are possible, for example, with the Voltcraft VC 54 and VC 185 models, as well as all VC 200, VC 400E, and VC 800 models except for the VC 830.
Reliable measurement with factory calibration
As part of the quality assurance process, all Voltcraft meters are factory calibrated. This ensures the high quality and compliance to tolerance limits as specified in the technical data in the operating instructions. A certificate is not included with DMM. If required, all models can also be purchased as an ISO or DAkkS calibrated version with a certificate.
Conclusion
The range of digital multimeters is vast and covers simple entry-level models to professional devices. Conrad Business Supplies’ 100, 200, 400, and 800 Voltcraft Series offer features that users should consider when choosing the device that best suits their specific measurement needs.
By Harald Lehner, Head of Private Label Product Marketing, Conrad Business Supplies
