April 2020

that meet the key requirements for these systems. Converters in this category are specified with superior dynamic range and THD (typically +108 dB DR and ?120 dB THD), which is achieved across a bandwidth of dc to at least 80 kHz, combined with ease-of- use features such as analog input pre-charge buffers, integrated digital filters, and cross- device synchronization for multichannel phase matching, make these key components in the building of the highest performance CbM data acquisition systems. Power scaling features allow the same physical hardware to be tuned to meet specific power ceilings, where dynamic range or bandwidth can be traded-off against total power. And providing accuracy at dc as well as wider bandwidth allows the input channels to address the needs of temperature, strain, and other dc or low bandwidth sensing in the same platform, which simplifies the overall condition monitoring system architecture and complexity—a single platform for all CbM sensor types. Simultaneous sampling In CbM systems, simultaneous sampling is used to ensure the phase relationships between sets of time domain data is preserved. For example, where two orthogonally arranged vibration sensors are used, this allows the direction and amplitude of the vibration phasors to be detected. Ideally the phase delays through each sensor input path should be well matched and track over temperature. For CbM systems that require even more flexibility in their design for wider range in their sampling rate, bandwidth, or power scaling needs, SAR ADC products are also appropriate. These devices also offer high dynamic range and THD, and at throughputs up to 2 MSPS, and also incorporate ease of use features that reduce signal chain power consumption, reduce signal chain complexity, and enable higher channel density. Converters with higher input impedance modes broaden the range of low power precision amplifiers that can drive these ADCs directly, while still achieving optimum performance. To allow system builders to achieve the highest possible channel densities in more compact or distributed acquisition nodes, and to achieve faster time to market, signal chain ?Module products with higher levels of integration than ever before are being developed. These ?Module devices combine key components commonly used in data acquisition signal chain designs within a compact, integrated circuit (IC)-like form factor. The ?Module approach transfers the design burden of analog and mixed-signal component selection, optimization, and layout from 18 | Plant & Works Engineering www.pwemag.co.uk April 2020 Maintenance Matters Focus on: Condition Monitoring the design. To achieve low noise in the data acquisition chain requires not only low noise sensors and analog-to-digital conversion components, but also low noise power design. And achieving low power in the system also requires power components that efficiently take power from the battery or field wiring without adding to the complexity of the design. Connectivity needs will depend on the specific application environment. Many industrial facilities already have extensive wiring in place for process control or existing environmental sensing, such as temperature. However, much of this existing infrastructure may not be able to deal with the large amounts of raw data, or the data rates, required for extensive condition-based monitoring. The future of CbM Condition-based monitoring is an absolute need for large capital cost equipment such as for energy and oil and gas, where unplanned downtime has a direct impact on production costs. It is also becoming more and more important on the factory floor where it can be used as both a proactive approach to machine maintenance, but also a way to ensure machines are producing product in a consistent way in normal operation. As the value of these monitoring capabilities becomes more apparent, this technology will start to be applied across more and more of the machines that we use every day—no longer the preserve of wind turbines or paper mills, we will see CbM in trains, planes, and automobiles, and eventually in washing machines and even smaller appliances. Manufacturers of system components will integrate the sensor, or even the whole channel, into the component. Motors will come with vibration and current sensing included, and the same may become true for bearings and gearboxes. There will be self-contained sensor nodes that will report to your mobile device— deploy one on your garage door so it can warn you before your car gets stuck inside. To meet the growing need for sensing in these many different scenarios, equipment makers will need to take a platform approach, where a smaller set of platforms can serve a more varied set of needs. Measurement channels will need to handle different sensor types so that rack-based equipment can be re- tasked for different combinations of sensors. In smaller equipment, the systems will need to be adaptable to different power profiles so that the same monitoring node can be used in a washing machine or a battery-powered tool. For more information on condition-based monitoring solutions from Analog Devices, please visit: analog.com/cbm designer to device, which shortens the overall design time and system troubleshooting, as well as ultimately improves time to market. Housed in tiny packages, ?Module devices are well suited to distributed low channel count, compact CbM systems or for higher channel count rack- based systems. Sensors Providing high dynamic range, wider bandwidths, greater power efficiency, and higher channel densities in the data acquisition part of the signal chain alone only addresses part of the system design challenge for CbM systems. Traditional integrated electronics piezoelectric (IEPE) vibration sensors are large, bulky, and expensive, and are usually run off relatively much higher voltage rails than the data acquisition system. Common piezoelectric sensors use a ?24 V single supply, consuming upward of 2 mA, and are housed in heavy metal cases. Because the sensor supplies are usually provided by the data acquisition module, increasing the channel density in the box becomes a power density problem and a component density problem. Adding to this the need for wireless battery-powered acquisition nodes, the traditional piezo vibration sensor no longer meets the demands of these signal chains. MEMS vibration and inertial sensors are now meeting the requirements of these systems. The latest wide bandwidth MEMS devices have noise and bandwidth performance that is ideal for CbM applications, and they achieve this performance in tiny standard surface-mount packages with power levels that are 20 times lower than comparable IEPE sensors. The small size and power profile of these MEMS sensors allow very small multiaxis, battery-powered systems to be developed for permanent and constant condition monitoring. Power and connectivity Sensing the temperature, vibration, or noise of the machine and converting this to digital information is a key part of the monitoring task, but these details do not provide the complete picture. To build condition monitoring systems requires paying close attention to all of the analog, digital, and mixed-signal components in