Engineer with safety glasses works on commercial vehicle engine in lab setting.
Turning up the heat on particulate emissions.

Advanced sensor cleans up diesel emissions as standards tighten. 

Regulations around cleaning up diesel engine emissions are becoming more stringent around the world, and meeting these standards is increasingly challenging. Although demand for gasoline and electric vehicles is increasing, light- and heavy-duty diesel vehicles are still part of the landscape, and as such, the call continues for better diagnostic and filtering tools. Delphi Technologies works to make all our technologies enable cars and trucks to drive cleaner, better and further. And our newest particulate matter (PM) sensor with direct temperature sensing capabilities is no exception.


How it works.

Before discussing our state-of-the-art PM sensor technology, let’s first think about diesel particulates and how PM sensors work.

The function of the PM sensor is to indicate when the diesel particulate filter (DPF) needs to be replaced. The DPF handles a lot of the dirty work, trapping the particulates (better known as soot) inside its walls. Any sort of breach or malfunction in the filter leads to soot being released into the air. The key to reducing these escaping particulates is to pinpoint exactly when the filter is about to, well, stop filtering. And that’s where the sensor comes in.

The sensor sits downstream from the filter in order to read particulate levels in the exhaust. Soot particles present in the exhaust cause increased conductivity in the sensing circuit inside the sensor. When the sensor hits a certain conductivity threshold, it tells the engine management system that the filter is in “failure mode” and needs to be replaced.


Timeline showing diesel exhaust flow


The problem with older generations of PM sensors is that they rely on non-direct methods of detecting a bad filter. These methods, such as differential pressure sensing, are not effective enough in detecting failing filters to meet increasingly stringent regulations. 

So rather than continue to settle for guesswork, we designed a sensor that directly detects soot particles in the exhaust, and determines when a filter needs to be replaced more accurately and efficiently. How? By integrating resistive temperature technology directly onto the sensor. 


How we made it better.

Even though it seems intuitive to put temperature-sensing technology directly on the sensor, it wasn’t as easy as it seems. 

To start, let’s think about this in terms of scale. These particulate emissions are extremely tiny. They’re so tiny that 3,000 of them stacked on top of each other would be as thick as a sheet of paper! Therefore, the sensors must be precise enough to actually detect the particles. Manufacturing such precise technology requires the latest and greatest laser-cutting technology, and designing it requires emission-expert engineers. Good thing we’ve got both. 

The solution we created uses a resistive temperature device (RTD) integrated into the sensor’s design. Leveraging special conductive metals and low levels of current, RTDs use changes in voltage, or electrical resistance, to gauge changes in temperature. RTDs have been long used in industrial and consumer technology applications and are a proven, accurate means of tracking temperatures. 

By integrating the RTD, we can now measure the sensor’s temperature directly without relying on indirect vehicle inputs, so it can clean the sensor more efficiently after it finishes with soot detection. It helps us meet plausibility diagnostics requirements and also improves the accuracy and speed of soot detection. 

To put it simply, Delphi Technologies’ PM sensor is more accurate and efficient than previous generations in controlling particulate matter being released from diesel engines. It’s cleaner, better, and will allow vehicles to go further by meeting rigid emissions regulations.   

Graphic with PM sensor snaking around multi-colored text.