Five things you want your DMM to support in 2021
Digital multimeters (DMMs) are among the most widely used pieces of electronics test equipment today, used in everything from electrical testing for the home, laboratories, field service, to bench instruments, Internet of Things (IoT) and sensor testing, factories automated setup and much more. DMMs are traditionally used to measure electrical values. Even the cheapest DMMs today, with basic resolution, typically may support features like auto ranging and a back-lit or color display. In addition to mandatory voltage and current (AC/DC) measurements, they may support measurements of resistance, temperature, frequency, and capacitance.
Technological advances have increased the demand for DMM functionality, especially for units used in lab benches. For 2021 and beyond, these are the five features you definitely want to consider in your digital multimeter:
● Cloud connectivity: the ability to seamlessly export data outside the unit without the use of USB sticks, but directly streaming data to some cloud repository and Interactive virtual dashboards for clear data visualization.
● Large sensitive displays and touch-screen interfaces on the unit.
● Programmability, to allow the unit making decisions based on data locally acquired, and mostly to speed up execution of complex actions including the control of other satellite units.
● A comprehensive software suite to control the unit from the laptop and create automated reports.
● A fast digitizer for the capture of transients without missing any data.
Next: DMM with cloud interface
1. Digital Multimeters with Cloud Interface Capabilities
DMMs were traditionally hand-held devices which displayed electronics testing information only on the device screen. There was no way to easily share this information with other people or push information to the Internet. State-of-the-art DMMs, like that shown in Figure 1, use a simple embedded app to connect to the Initial State IoT data streaming service, which can monitor and log data streams directly from the DMM instrument. Users can set measurement thresholds and receive email and text alerts when a threshold is reached directly from the dashboard.
Figure 1. Dashboard and Cloud data sharing make signal analysis portable from instruments to mobile devices
Initial State software-as-a-service platform integration gives the DMM remote monitoring capabilities, and also real-time interactive dashboards for data visualization, triggering and the ability to share data—all without the need for a PC or external software. The remote access feature allows users to monitor and analyze electronic data from the DMM remotely in any browser including on mobile devices anywhere in the world. This capability is available also for multi-channel DMMs, the so called “data loggers”, like the DAQ6510 which supports scan cards for multiple signals monitoring.
Figure 2. Tektronix Keithley DMM6500 DMM with Initial State Internet and Cloud Capability
2. Large displays and Touch Screen interfaces
Modern DMMs have large touch screens and interactive dashboards which make it easy to view multiple lines, use virtual buttons, and have electronic signals displayed on the DMM screen clearly visible also in factory floors, where units are often more distant to the operator than in the lab.
Figure 3. Large Touchscreen Interface with oscilloscope “like” signal analysis
The “pinch and zoom” characteristic of a touch screen display makes these highly complex devices as simple to use as an everyday mobile phone, and extremely familiar for new generations of engineers.
3. Programmability in Modern DMMs
DMMs have traditionally used the Standard Commands for Programmable Instruments (SCPI) programming interface as uniform and consistent language for the control of test and measurement instruments. Previously, this was the only programming method available on a DMM. However, modern DMMs need programming flexibility to automate measurements to save time and mostly to meet demanding throughput requirements.
Figure 4. Functionalities and measurements setup should be accessible either from intuitive UIs and from API and functions to program
Modern DMMs often allow users to write their own code in languages such as Python to control the unit. In addition, DMMs may include factory installed applications which let users customize the user interface, change the display or how information is automated. The DMM shown in Figure 2 contains an embedded microprocessor and includes a Test Script Programming (TSP) scripting language which allows users to enter control commands and write test scripts than can be downloaded and stored inside the instrument itself.
4. Comprehensive Software Suite and Interaction with Other Units
Modern DMMs now include expanded capabilities for other electronic measurements, including capacitance, temperature (RTD, thermistor, thermocouple), and diode testing with variable current sources. The DMM shown in Figure 1 is supported by a software application called KickStart. Kickstart is an Instrument PC Control Software that allows users to configure, test, and collect data from multiple instruments (including DMMs, power supplies, SMU instruments, dataloggers, sensitive units like electrometers and even several models of Tektronix oscilloscopes). Users can control up to eight instruments at the same time and retrieve millions of readings from each instrument. The software contains plotting and comparison tools that help discover anomalies and trends.
Figure 5. Tektronix Keithley software suite control panel allowing full bench control and measurements reporting
Users can save test configurations and export data for additional analysis or to share test updates. The key thing with these evolved software suites is that they are regularly maintained and improved, and the licensing modeling allows the use of a floating licence as well as annual license purchases as a more affordable alternative to a perpetual licensing purchase.
5. Fast Digitizer
When selecting the right DMM for you, resolution and accuracy are the main parameters to consider. Resolution is the level of detail that is measurable and displayed on the DMM, typically a number consisting of an integer and a half such as 3 ½ up to 7 ½ digits. The resolution of a DMM depends on the embedded ADC (analog-to-digital converter) used and on the maximum number of its counts during a full conversion. While DMMs with high resolution typically have high accuracy, these two specifications are not the same. Accuracy depends on digitizer accuracy, but also on noise level, stability of internal references and tolerance of all the electronic components used to design the DMM itself among other qualities.
But the speed of the digitizer matters as well. A fast digitizer–is an essential feature to consider when choosing a DMM. Some Keithley modern DMMs integrate a –1-MS/s) 18-bit digitizer that provides an oscilloscope-like view of the signal being measured and allows users to capture fast transients, typically needed in the IoT space, combined with high accuracy and resolution.
Figure 6. Fast Digitizers on modern DMMs can help tracking rapid signal changes
A fast digitizer can capture the current power drain in all the states of an IoT product from the low power sleep mode to the full power transmit mode and load current burst. Capturing a profile of the load current allows the user to calculate an average drain current value, which is key to assess battery life based on the capacity of the battery powering the IoT device. Example of using DMMs in multichannel complex factory testing environments DMMs, when combined with switch systems, can offer precision measurement capability to a large number of channels. These high channels or high capacity DMMs are often referred to as DataLoggers, and instead of serving labs they are used mostly for assembled product manufacturing testing. Let’s take the basic example of temperature scanning, one of the common measured physical parameters. Temperature measurement of devices typically involves taking measurements in an environmental chamber with thermocouples, using the plug-in switch modules that have automatic cold reference junction compensation for thermocouple measurements.
Figure 7. Dataloggers mainframes can embed multiple channel mux and scan cards for tracking processes and signals in the industrial environment
The DAQ6510 is essentially a DMM supporting a selection of plug-in switch modules and a wide range of functionalities offering all key five features mentioned above, including Cloud datastreaming, support of KickStart Instrument Control Software, resolution, fast scanning, and a touch screen interface.
Digital multimeter (DMM) test instruments have been used for decades to measure electrical values. DMMs have now moved into the digital age with features such as cloud streaming and interactive dashboards, touch screen interfaces, programmability, remote software control and fast digitizer features. Using older DMMs may hold back engineers from testing at the speeds and with the flexibility they need for today’s increasingly complicated devices. From connected homes and buildings to advanced automotive solutions and wireless communications, new DMMs can help drive digital product innovation.
Andrea Vinci is EMEA technical marketing manager) at Tektronix. He is responsible for the Keithley products portfolio. He holds a MSc in electronic engineering from the University of Padova and has more than 20 years’ experience in the electronics and T&M industry.
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