PDS Pressure Pulse Transducer

The sensor is meant for recording the forms of pressure pulsations in the intake manifold, crankcase ventilation system or engine exhaust system. This allows estimating alignment accuracy of the value train, defining if the clearance between the piston and cylinder wall is excessive, checking cylinder balance as well as detecting misfiring in the cylinder without taking an engine apart. 

Sensor Design

The sensor case is made of caprolon (polyamide), which makes it heat-proof and resistant to deleterious substances while being tough and light. Sensor’s connecting tube is made of brass and can be connected to rubber tubes between 4-7 millimetres in diameter. A soft cable with a high density braided copper shield to minimize noise pickup so you can get high accuracy of the measured signal. 

Waveforms samples

Video Tutorials

Diagnosing a valve timing with the help of the PDS pressure drop sensor and automotive oscilloscope, connecting the sensor to the engine, oscilloscope tuning, waveform recording while idle running and cranking. I’ll demonstrate all of this with an example of a Subaru Impreza.

A review from the GADGETS playlist for PDS pulse transducer

A review from Back Alley Diagnostics for PDS pulse transducer

A review from Mechanic Mindset for PDS transducer, Lx4 sensor and TL-mix4 test lead

Discovering where the pulses in the coolant tank are coming from with the help of the ROTKEE Pulse Sensor and the PicoScope 4425A. By Mechanic Mindset

Sensor Operation Principle

While working an engine produces a series of pressure pulsations in intake and exhaust manifolds. This happens because intake and exhaust valves open and close in a certain sequence, redistributing the streams of fuel air mixture and exhaust gas. Every time an exhaust valve opens and burnt gases come out of the combustion chamber, there’s a high-pressure pulse in the exhaust system. Procedure of similar nature takes place in the intake manifold as well. A lot can be inferred from the pressure in the crankcase. Pressure pulsations in there indicate bleed-off piston rings.

The sensor consists of a film with piezoelectric crystal plate, which interacts with the pressure in the measurable area. As the pressure rises, the plate bends. When the pressure is back to normal, the plate resumes its shape. As piezoelectric materials produce an electric charge while undergoing deformation, electric voltage occurs on the surface of the plate, which is virtually proportional to the material pressure.

One of the sensor’s features is that it can be used for displaying dynamic pressure. It can’t measure static pressure, because as soon as pressure becomes static, piezoelectric ceramics ceases to deform and therefore stops producing electric charge. Meanwhile, the charge stored on the plate bleeds to zero due to losses in the material or meter. In practice, it makes no difference to diagnostics though, as while an engine is working, the pressure constantly changes in all systems indicated. Using piezoelectric ceramics as a measuring element allows significantly reducing sensor’s price without affecting measuring accuracy. Another advantage is that there’s no need to use an external power source. This is what makes this technique universal and able to be used on any internal combustion engine, as a depression sensor requires no tuning control while in use.

The sensor is compatible with any oscilloscope.