Sentelligence Technology

Introduction

Over the past five years Sentelligence has developed a flexible platform technology that can be applied to a wide range of fluid condition and quality monitoring for automotive, mining, and industrial applications. The primary technology is a universal optical platform that measures the spectral or optical response of the fluid and correlates this to specific properties. The sensor components are solid state and are selected to perform in the rigorous conditions encountered in commercial engine, transmission and hydraulics applications, under normal extremes of temperature and vibration. The primary optical function monitored is light/energy absorption in the visible and near infrared regions of the electromagnetic spectrum. Extensions can include light scattering and optical emissions, such as fluorescence. Both additional forms of measurement are useful diagnostics for the characterization of specific fault conditions and/or the presence of undesirable materials. In their primary intended use the sensor devices interact directly with the medium (fluid) that is being monitored. Alternative configurations are possible where the measurement is made indirectly or after some form of chemical modification of the interacting medium. This can extend the role of the sensors into the measurement of reactive gases and vapors, such as carbon monoxide (CO) and NOx.

Intelligent Sensing…the Concept

The company name, Sentelligence, is derived from the terms defining the functionality and fundamental principles of the sensing devices – that is “intelligent sensing”. All the sensors have onboard data handling functions that provide full sensor control, data acquisition, data pre- and post processing, communications, and fault and condition diagnostics. In the case of the condition diagnostics, the term condition relates to the fluid. For this type of measurement the sensor monitors specific signals and trends. For example; in the oil condition monitor the sensor keeps track of events such as oil changes and top-offs (see Figure 3b). However, it also tracks the trend in terms of rate of change and direction (see Figure 3c). Both trend rates and changes to trend rate, as well as to deviations to the normal trend direction are highly diagnostic and can be correlated to a number of performance conditions, including abnormally high fuel consumption and also adverse conditions such as filter plugging and/or dispersant failure. More discussions on this will be covered later. In a second scenario, as in the sensor configured for urea monitoring for diesel engine SCR systems for NOx reduction, both trends and specific signals are diagnostic. The trends are of concentration, which ideally should be within the prescribed 30% to 40% urea content range. Whereas specific signal responses can be equated to the use of the wrong fluids; which could range from water, to coolant, to even fuel…all being highly diagnostic. Sentelligence sensors are designed for maximum functionality and flexibility (programmability).

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Core Sensor Technologies

The key to the Sentelligence sensor technology is the combination of selected opto-electronics to provide the desired optical or spectral response within a given application and/or fluid environment. Almost any change in properties or fluid performance can be correlated to these optical/spectral responses with a suitable selection of sensing components (for wavelength and/or responsivity). These are combined by the optimized coupling to an optical interface, which is designed to meet the needs of a specific application and/or operating environment. Generally, the optics are non-conventional and highly optimized to ensure efficient coupling of the key optical components with the sensing element and the fluid. In the standard sensors the wavelengths considered range from the short-wave visible (around 400 nm) to the end of the short-wave near infrared (around 1100 nm). Combinations of wavelengths, and optical response characteristics provide a raw output that can be processed and correlated with changes in fluid condition and chemistry. Not all responses measured are the same, and light emission (fluorescence) and light scattering (nephelometry/particulates) can be evaluated with the common optical layout of the main optoelectronic components. As noted in the introduction, this is not necessarily limited to direct spectral responses, and optical/spectral response changes induced in a secondary phase can be used for vapor/gas, as well as specific fluid systems, such as for pH measurements.

Figure 1: Functional layout of the Sentelligence Optical/Spectral Sensors

A generalized layout of the Sentelligence optoelectronic sensor is provided in Figure 1. This provides a functionalized schematic for the sensors, where the optical interface and the optoelectronics are customized for individual applications. The customization is based on the selected wavelengths and the selected geometry/dimensions of the interface. In terms of the standard configuration, up to four wavelengths can be independently monitored by the coupling of the source to an independent set of optical detectors. Individual wavelengths can be differentiated by position and/or modulation frequency. The optical interface can accommodate more wavelength if desired, with a possible maximum, based on current geometry of eight. This is more than sufficient for even the most sophisticated applications. Most applications are handled by the default of four wavelengths. The sensor also features a reference detection system that monitors the source emissions from the opto-head, prior to the optical interface – an important factor for certain photometric measurements.

Figure 2: Diesel Oil Condition Sensor

The data acquisition and signal conditioning is handled by the on-board electronics, as well as the data processing and fluid condition assessment. Figure 2 is an example of one of the Sentelligence optical sensors, designed for diesel engine oil condition monitoring. This sensor monitors the presence and rate of formation of the insoluble combustion products (primarily soot) as dispersed in the oil. The level of the insoluble contaminants can be correlated directly to oil condition, as well as other related oil parameters that are linked to oil lifetime and usages, such as base number and viscosity (for a defined lubricant system). These parameters alone provide an important on-vehicle condition metric. This is a true real-time measurement and important trend information is provided by comparisons to normal versus abnormal sensor responses for different operational conditions and performance parameters…including fuel consumption and oil additive functionality (dispersant dropout). The latter can occur at severe levels of contamination, including coolant contamination which can coagulate the insolubles (soot) and the additives. Examples of the diagnostic detector responses are provided in Figures 3a,b,c.

3a

3b

Figures 3a (top) sensor fluid performance indicator and 3b (bottom) the predicted normal sensor response

3c

Figure 3c example sensor trend diagnostics

In figure 3c, the normal trend rates for the oil condition response are designated by R₀ to R₂, with R0 being the norm. R_A is an abnormal trend, being higher than predicted, and would be diagnostic of over-fueling and/or a higher than normal rate of fuel consumption. A lower than normal rate, R_C may or may not abnormal, but a sudden change in rate change might be indicative of a change in performance or a change in engine operating parameters. Note that it could be a situation where the engine is running lean, which can lead to higher than normal NOx. The more important rate change are those represented by AC_S1 and AC_S2, where the norm is to a positive rate change. No rate change or more significantly a negative rate change are both indicators of undesirable situation…such as high levels of dilution (possible fuel dilution) or loss of insolubles, which is not normal and could be indicative of an unacceptable contamination or the consequences of high levels of contamination.

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Meeting the Needs of Specific Sensor Applications…

The Sentelligence sensors are fully programmable. The electronics include a boot loader which enables sensors to be reprogrammed and recalibrated, as required. In the case of the condition monitoring versions of the sensor they can be set up to handle the various scenarios depicted in Figures 3a-c. Note that these are defined for a diesel engine, but similar or comparable scenarios can be defined for other forms of engine combustion (gasoline and natural gas), liquid fuels, transmission fluids and hydraulics. Likewise, for certain systems, specific contaminants can be defined, as indicated earlier for the urea sensor. In examples such as fuels, this can include water and asphaltenes. For systems such as coolants, certain reactive species may be monitored, such as certain inhibitors, or the bulk acidity (nominally as a change in monitored pH). Currently two forms of the sensor are in the final stages of development, leading to deployment. Customization to meet the needs of specific applications is quite practical and because of the platform design, a practical measurement system can be tested for concept within a few months. For certain applications this can be emulated prior to any reconfiguration a simple laboratory model.

The current fluid sensors can be adapted to a wide range of liquid media applications. As noted, with minor modification they can be adapted to monitor certain gases and vapors. Examples can include oxygen, carbon monoxide and the reactive NOx gases. The principles of signal handling, signal conditioning and data extraction can be extended within a platform-style concept to make base measurements beyond the current optical/spectral detection. Applications of spectral measurements derived from electrical property measurements and electro-magnetic measurements can extend the applications beyond those currently defined for the optical sensors. In the latter case, a technology has been identified to monitor the onset of wear. Sentelligence is planning to include a wear detection sensor in its portfolio of sensors in the near future. Example current and target applications for the Sentelligence sensors are listed below in Table 1.

The Sentelligence sensors are designed for low-cost high volume production. They have the potential to address areas of application not covered by Table 1. End users and OEMs interested in other areas of application should contact Sentelligence for an assessment.

Table 1: Current and Projected Fluid Sensors – Functionality and Application

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