Creative Low Power Solutions for Field Instrumentation & Factory Automation

For more than five decades, Analog Devices has led the electronics industry in the development of analog building blocks for precision signal chains. A recurrent theme which has emerged more strongly in each successive decade has been the demand for low power operation without compromising the accuracy, stability and linearity for which ADI products are renowned.

Now, in ADI’s latest Precision Low Power Signal Chain, these capabilities come together, providing applications such as instrumentation for factory automation and industrial process control with the complete ultra-low power measurement solution that they need.

Saving Space as well as Power

The modern factory or process plant has an immensely sophisticated control system – the facility’s brain – to co-ordinate and regulate its operations. This brain at the center relies on a huge array of remote sensors – the system’s eyes and ears – to monitor the state of the processes running in the factory. These sensors typically measure parameters such as pressure, temperature, or flow rate. And in the latest artificial intelligence (AI) systems supporting functions such as condition-based monitoring (CbM), the sensors might be monitoring vibration or sound to detect the tell-tale signals of an impending machine malfunction.

These sensor modules are deployed remotely, as discrete units and require a communications interface to the main control system. Some field instruments are so physically remote that they are battery-powered, due to the distance from a power supply cable. Low power operation is essential to extend run-times before an instrument’s battery needs to be replaced. This translates directly into reduced maintenance effort and cost – a crucial contributor to improved factory productivity. Even in loop-powered 4-20mA solutions there is an increased challenge of developing a system that can operate effectively within the limited power available. 

Field instruments also tend to be small, enabling them to be squeezed in among pipes, valves, and other infrastructure.

An Adaptable, Integrated Signal Chain Platform

This requirement for power and space optimization inspired ADI to create its latest Precision Low Power Signal Chain (See Figure 1). The keys to the value of the signal chain are integration, power optimization, and adaptability. At its heart is the new AD4130-8, a highly integrated ultra-low power 24-Bit Sigma-Delta ADC which can perform biasing and excitation of many common sensor types such as pressure and temperature sensors, as well as providing high-resolution digitization of filtered analog signals. An on-chip FIFO buffer helps reduce the processing overhead on the host microcontroller, and integrated diagnostics detect when sensor inputs are absent or malfunctioning.

Integration of these functions into a precision multiplexed ADC reduces the total component count and helps the developers of field instruments to realize more compact designs.

At the same time, a Precision Low Power Signal Chain based on the AD4130-8 can deploy a range of power optimization techniques such as duty cycle control to minimize system power consumption.

Since the AD4130-8 based Power and Density Optimized Signal Chain is highly adaptable, instrumentation manufacturers can easily reconfigure/adjust their solution to build a family of products, which reduces development time and streamlines both inventory and production. The multi-channel AD4130-8’s internal sensor biasing and interfacing capability provides a direct connection to a sensors' measurement modalities such as temperature, load, and pressure making it easy to acquire data on these parameters.

Other modalities, such as flow are also readily supported with the addition of a minimal number of external components, making it an adaptable base design that supports a variety of different sensor types and applications.  Also included with Precision Low Power Signal Chains, is the appropriate power management components to maintain ultra-low power and accuracy.

Figure 1 - Configurable, Integrated, Power and Density Optimized Signal Chain

Ecosystem of Support Tools

When field instrument designs are based on Precision Low Power Signal Chains, developers can take full advantage of the array of tools and support tailored to it.  This includes the newly released noise and AC simulation tool from ADI’s Precision Studio. This tool quickly simulates the circuit's AC and noise performance, showing results in real time.  It will also generate schematic blocks based on user inputs (for example gain, level shift, and 3dB frequency).  Once the schematic is built and simulated, it can then be exported to our LTspice® simulation software for further fine tuning.  This tool is an example of how Precision Studio shortens the design time to an optimal circuit, by allowing quick iteration to meet the particular application's requirements.  

There is also a dedicated EngineerZone page for Precision Low Power Signal Chains to provide support for any questions system designers may have.

Single and Multi-Channel Signal Chain Options

The new AD4130-8 ADC provides the basis for a power- and density-optimized precision signal chain. ADI also provides other Precision Low Power Signal Chain options for applications which require only single-channel measurement, or which require different optimizations, such as for noise, or for handling biopotential signals.

This wide choice of low power signal chain designs, all supported by ADI tools, documentation, and evaluation software, means that designers of low power sensing systems have at their fingertips all the resources they need to quickly refine the base design, adjust for their unique conditions and create their solution.