Exploring the Value of the PXB’s VMCB Multichannel Function
The PXB is a robust tool that can be applied in a massive range of test scenarios from battery cycling and eAxle testing, to DC-DC power supply testing. The quality of the PXB along with its range of functions makes it an indispensable tool in lab environments for prototyping and initial product testing. This utility is further extended by its multichannel function, also known as virtual multichannel bus (VMCB), in which multiple PXBs can be connected and remotely controlled to scale testing to multiple devices under test (DUT). The VMCB function allows up to eight units to be connected to a PC; these eight units sharing a domain can be integrated into an even larger network to further multiply facility testing and make efficient use of plant space. This article discusses the difference between the VMCB function and multichannel power supplies, the benefits of the PXB in various test environments, and the specific benefits/uses of the multichannel channel function.
Multichannel Power Supplies vs. the PXB’s Multichannel Function
A multichannel power supply integrates multiple isolated power outputs (e.g., +12V, -12V, +5V, +3.3V) to drive electronic testing from a single AC input. Often applied in test and measurement use cases, these systems primarily provide multiple power-isolated channels in a small space. These power supplies specialize in testing complex DUTs that require multiple supplies to different circuitry and possibly at varying sequences (i.e., analog, digital, etc.). Multichannel power supplies are good options to supply common voltage rails in PCBs — different from the PXB’s VMCB function.
With the multichannel function, a single source controls multiple programmable PXB power supplies. This capability elevates the PXB bidirectional power supplies’ utility, enhancing its value in the test engineer’s repertoire.
The Utility of the PXB in Various Tests
The PXB is a bidirectional programmable DC power supply with regenerative capabilities. The bidirectionality allows the device to function as both a source and a sink (Figure 1), performing the functions of both the power supply and electronic load in battery cycling (charging/discharging) testing, DC-DC converter burn-in testing, or testing the regenerative functions of motors (e.g., eAxles). The on-site regenerative capability returns power to the local grid; when the PXB functions as an electronic load (sink), instead of dissipating the excess power as heat, it redirects the power to the local power grid. On a small scale, this capability saves a test lab a marginal amount of power. However, in scaled operations for a larger test facility, the power recycled can be substantial over time. This dynamic is further improved by lowering or even eliminating the HVAC costs that come with cooling off the radiative heat. The PXB can also simulate the internal resistance of a battery, fuel cell, or solar cell, making it a useful tool for testing automotive components such as eAxles or solar inverters.
The PXB’ additional benefits include performing complex waveform profiles with relative ease via the PXB’s built-in web server. A total of 30 programs can be created and linked for up to 10,000 steps (with all programs combined) to automate and remotely monitor tests. An internal data logger also records all measured data for further analysis. Overall, the PXB is well-suited for automated tests for DUTs that are typically challenging to test or are subject to a high level of regulation. These tests grow even more challenging when attempting to scale them up — automated testing can be difficult with many different complex sequences run over an array of test equipment. The multichannel function directly addresses this potential scale-up obstacle.
Figure 1. The various functions the PXB can perform and applicable tests that might benefit.
What is the Multichannel Function (VMCB)?
The VMCB function of the PXB allows users to connect one computer with up to eight units to construct a virtual multichannel power supply system, a function that:
- Reduces the number of communication ports and,
- Controls the multiple units of PXB together.
This function allows multiple DUTs to be connected concurrently for prototyping or product test scenarios, synchronizing multiple tests on different DUTs. To use this multichannel function, users can connect a PC to the PXB via a switching hub or a broadband router as shown in Figure 2.
Figure 2. To use the multichannel function, the PXB can be connected to a switching hub/broadband router, which is, in turn, connected to a PC.
The series VMCB function allows the PXB to be used efficiently for remote control and monitoring with 1-to-N and as well as N-to-M in large-scale networks (Figure 3). The LAN interface is LXI compliant, allowing users to control and monitor the PXB from a browser on a PC, smartphone, or tablet. The power supplies can also be managed from a different building. This function greatly scales the reach of production testing, controlling all automated tests from a single device.
Figure 3: The virtual group (with the same domain number) can be part of a larger-scale N-to-M network, extending the number of PXB tests that can be performed simultaneously on DUTs.
Commands can be sent from the PC to control the PXB by setting the following functions (Figure 4):
VMCB enable: Enabling virtual multichannel bus (VMCB) function (System → VMCB → Edit).
Master/slave unit: Setting up the master and slave units on the PCB connected to multichannel. The PXB unit set at the VMCB slave units are controlled by the VMCB master unit.
Domain number: PXB units that have the same domain number can be controlled as one VMCB network.
Channel: Channel numbers are used to identify each VMCB slave unit when they are controlled from the PC using commands.
Figure 4. The VMCB window can be accessed under “System” on the PXB to enable the multichannel function.
Benefits and Uses of the Multichannel Function
Synchronizing many PXBs to perform mass testing comes with benefits including:
- Simplifying control
- Ease of installation (fewer communication ports are used)
- Efficient use of plant space (PXB can replace multiple equipment)
- Lowering the barriers for setting up a production test facility (i.e., designing a test for a single PXB is easily scaled)
The multichannel setup ensures that test designers are using fewer communications ports to synchronize testing. This simplifies control and eliminates the challenge of setting up unique test benches. Instead, a single test setup can be programmed and executed across multiple PXBs at a distant location, accelerating the process from the ideation phase, design, and installation. The PXB performing multiple functions (Figure 1) allows designers to save valuable floor space.
Quality testing, or end-of-line testing in manufacturing facilities can benefit from the VMCB function as these tests are often simple functions performed repeatedly at speed. This ability potentially accelerates research and development (R&D) testing in which multiple DUTs can be tested simultaneously to quickly assess the behavior of different prototypes. The PXB can test the battery by easily performing charge and discharge cycles, and it mimics the behavior of a battery making the possible DUTs range from inverters to motors, and converters. These DUTs are prolific and are often used in highly regulated fields such as automotive, aerospace and defense, military, and medical industries, forcing components to pass stringent tests to be within compliance.
Massive testing labs for batteries can include thousands of cycling channels and hundreds of environmental chambers (Figure 5). These labs require a centralized method of control across devices to synchronize, thus simplifying testing. The PXB assists with the process of scaling up testing with minimal complexity, lowering the barriers for testing multiple DUTs.
Figure 5. The Idaho National Laboratory’s (INL) battery testing lab. Source: Wikimedia Commons
Conclusion
The PXB programmable power supply performs a slew of functions that make it a useful tool in an engineer’s test bench. However, scaling tests up for multiple DUTs can be a significant barrier to introducing test equipment from the lab environment to the production environment. The PXB’s multichannel (VMCB) function ensures the PXB can maintain its utility in larger-scale tests by controlling multiple PXBs via a single PC. The LXI compliant interface ensures users can control and monitor PXBs from a browser on a PC, smartphone, or tablet at a different location. This way, testing remains simple and relatively easy to set up.
