Abstract: The AD73360 is a highly versatile programmable three-phase power test integrated circuit designed for industrial meters and multi-input systems. This paper discusses the design and implementation of a multi-channel data acquisition system built around the combination of ADSP-BF531 and AD73360, specifically tailored for use in power load control terminals.
Keywords: Data acquisition; Power load; AD73360; ADSP-BF531
Introduction: The power load control terminal serves as a critical monitoring device located at the user end. Its primary responsibilities include collecting data, controlling user loads, and facilitating communication within the power load management system. As the backbone of such systems, it not only receives remote commands from the load management center but also executes local power and load control based on predetermined power consumption targets. Additionally, it relays users' power consumption statistics back to the center.
The accuracy of data acquisition in these terminals is paramount, directly impacting overall system performance. For periodic electrical parameter measurements, simultaneous sampling is essential for precise real-time signal analysis. Beyond just measuring voltage and current levels across each phase, the system must also assess the phase relationships between them. Consequently, the ability to simultaneously sample multiple signals is crucial. In our development efforts for this terminal, we opted for the digital signal processor ADSP-BF531 as the core of the system architecture. Simultaneously, the AD73360—a 16-bit analog-to-digital converter—was chosen as the central component of the system's front-end stage. Practical experience has shown that the AD73360 excels in analog front-end operations for power parameter measurements, offering both precision and stability.
1. Introduction to AD73360: The AD73360 is a sophisticated, general-purpose 6-channel 16-bit precision serial analog input front-end processor manufactured by Analog Devices (ADI). It functions as a three-phase power testing IC for industrial meters or multi-input systems. Each channel includes a signal conditioner, a programmable gain amplifier (PGA), an analog sigma-delta modulator, a sampler, and a serial port. Given its internal PGA and dedicated analog front end, it can handle small-scale sensor signal acquisition directly. Although sigma-delta ADCs typically don't demand high-precision analog circuits, converting standard signals into differential signals is often necessary before acquisition. Fortunately, the AD73360 features a signal conditioning module on its front end, allowing inputs to be either single-ended or differential. This reduces the number and complexity of peripheral circuits needed.
The AD73360 is particularly well-suited for industrial control applications requiring simultaneous sampling. It performs excellently in both large-signal and small-signal scenarios. With six analog input channels capable of simultaneous sampling, these channels operate independently without CPU intervention. This setup minimizes phase errors caused by differences in sampling times. The sampling rate per channel can be easily configured via control words at 8 kHz, 16 kHz, 32 kHz, or 64 kHz, making it ideal for three-phase power operational parameter measurement and control systems (simultaneous three-phase voltage and current sampling).
Moreover, compared to parallel interfaces, the AD73360 employs a six-wire industry-standard synchronous serial interface to connect to the CPU. This simplifies hardware connections, reducing printed circuit board space while minimizing electromagnetic interference, thus enhancing system reliability and stability.
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