Scoping portable requirements
25 October 2017
All products need testing, both in the design and development phase, as well as once they move into production – with different requirements at each phase. Another consideration sometimes overlooked is the need for engineers to test products post-manufacturing in the field.
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This article from Yokogawa Test and Measurement discusses how engineers can benefit from its new DL350 ScopeCorder, which is designed for use in the field to assist in the detection of quality and performance issues.
No electrical engineer likes to hear that a product they worked on is subject to a recall – or worse – a safety issue. But, it’s becoming more and more common as every product seems to contain increasing amounts of embedded electronics and circuits. When it happens, the product is usually returned to the laboratory to be examined, to identify the root cause of the issue so it can be fixed. However, in some instances, it’s much better to get out into the field – to understand the exact characterisation of the situation where and when the issue is encountered. Vehicles and large appliances are good examples of this.
Today’s automotive engineers face challenges in two key areas. Firstly, the detection and remedy of design and manufacturing issues, and particularly the need for rapid fault identification, so that solutions can be speedily implemented. Secondly, as electric vehicles are increasingly accepted as alternatives to fossil fuel, their propulsion and energy storage system performance has to improve in efficiency and effectiveness. Both these challenges require laboratory-quality instruments that can be used in the field to measure and record ‘real-life’ operational situations.
To undertake these types of investigations, engineers need to establish a similar testing environment to that found in the R&D laboratory – but in a production environment. The following factors need to be considered:
- the number of instruments needed (for instance, power analysers, vehicle bus monitors, multi-function oscilloscopes or data recorders);
- the precision, accuracy and sampling rate required to detect any performance anomaly;
- the battery capacity to power the instruments (however long they may take to run the tests);
- and how to use them in a production vehicle, rather than on a test platform.
A new way of thinking about mobile measuring instruments
To address these requirements, Yokogawa has developed a compact lightweight portable instrument that allows automotive engineers to make more accurate and precise measure-ments, and record them over long periods of time.
The DL350 ScopeCorder combines the features of a general-purpose oscilloscope with those of a high-performance data acquisition recorder, in a single, portable instrument. Unlike alternative portable measuring solutions, such as portable oscilloscopes or combined oscilloscope/multimeters, it adds exceptionally high levels of precision and accuracy to field measurements; isolated inputs for measurements at high voltage levels; and large-memory capabilities that allow long-term recording for many hours – even days.
Another key feature of the DL350, not usually offered by other portable instruments, is its plug-in modularity, which allows it to be configured to suit a variety of user applications. This flexibility is achieved by incorporating two slots, which can be populated with any of 18 different types of user-swappable input modules.
This means that four isolated 16-bit voltage inputs can be measured at speeds of megasamples per second (MS/s), alongside 16 temperatures or two separate CAN or LIN buses, each containing 60 signals. Changing a single module enables measurement at 100 MS/s with 12 bits and 1 kV of isolation. Meanwhile there are 16 logic inputs always available, with even more available by swapping in a further module. Up to 5 Gpoints of data per channel can be recorded directly to an SD card. This means that the DL350 can be used for continuous recording – for up to 50 days.
The DL350 is based on an A4-sized chassis and weighs under 4kg with a battery and 2 x 4-channel modules included (or 2.6kg without either). The built-in rechargeable battery provides three hours of continuous operation, which, when combined with either mains or 10 to 30 V DC power, provides the DL350 with a highly reliable power supply and worry-free recording for tests that are difficult or expensive to repeat.
Engineers have the choice of a simple level trigger, or enhanced triggers, on such things as pulse width, waveform period – and across multiple channels. For example, the wave window trigger is ideal for AC power-line monitoring, and enables voltage sags, surges, spikes, phase shifts or drop-outs to be easily captured (available for 40 to 1000 Hz waveforms).
The ‘CAN monitor’ function enables monitoring of CAN frame data as trends. The trends are displayed as waveforms, and can be compared with other analogue waveforms. Waveforms obtained from the signals in the CAN or LIN-Bus data can also be used as the physical value trigger source.
Measuring it all up
We are already seeing innovative applications of the DL350. In one example, a hybrid EV manufacturer is using it to check the performance of wireless charging circuits for electric vehicles, whose next generation will no longer need to be plugged in to charge – rather, owners will simply have to park in a charging bay. However, the better the alignment of sender and receiver, the higher the charging efficiency. The more deviation, the slower the charge – and it also has implications for the lifetime and performance of the battery. Using the optional GPS module to indicate the parking position, the DL350 monitors the variation in measured voltage and current when charging.
Using two lightweight portable DL350s, the manufacturer can map the transmitter and receiver to correlate data of the complete charging process and system. Because the DL350 uses Yokogawa’s IsoPro isolation technology, it isn’t prone to inaccuracies caused by the surrounding electrical systems, inverters, power supplies, and so on. Having a large memory and long duty cycle, the DL350 can record for the entire time it takes for the charging circuit to recharge the battery under test.
Another success has come with a motorcycle manufacturer, who chose the DL350 for its compact lightweight form factor, enabling it to be easily attached during long run durability testing, as well as for the flexibility of its modular design – which allows the instrument to be adapted to the test being carried out. Previously, they were using standard benchtop instruments, but the bike was then difficult to ride and therefore it was hard to recreate authentic conditions. In addition, the test bike required further adaptation to run different tests – or the use of multiple bikes for different tests.
With the DL350 ScopeCorder, engineers can now see precisely what happens to automotive systems in the field – the real-world production environment – rather than trying to simulate/emulate conditions in the laboratory, or build complex vehicle-mounted test rigs.
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