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DIY Pressure Transducer question and build probably soon

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3 years 10 months ago #40097 by John Curtis
Hey folks, have any of you built your own pressure transducers? I’m going to tackle a build soon and thought I’d see what you guys have used for yours along with possibly some captures and any input you have before I jump into it.

I’ve noticed on some builds you don’t see all 4 cycles. On the two builds shown in the videos below you can see everything a WPS500 would show, maybe not with the voltage and resolution but enough to diagnose for sure!

Here’s what I’m planning on copying


And here’s a similar one in use

Making Pressure Differential Sensors (PDA Sensors) for pressure pulse diagnostics.
Currently servicing Central Texas.

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3 years 10 months ago #40099 by Dtech494
For the small investment it is worth trying and making your own transducer.
Some of them do not give the best transitions or resolutions. So it may be hit and miss. Often if you AC couple you get the best signal to display.
Input voltage and scaling on your display can also make a difference.
Some transducers are designed better for displaying rapidly changing pressures.
But if you make a harness and use that 3 pin connector (GM TPS ) style connector then you can easily swap them.
You will likely find having a 300 psi and 100 psi one to be useful.
The 100 psi one displays running compression better while a 200 or 300 psi one is better suited for cranking compression.
For vacuum waves a GM map sensor works excellent (with a 9v battery supply)
A GM fuel tank pressure sensor makes a good tail pipe pulse indicator (with a 4.5 volt battery supply.)
Or a peizo buzzer closed in a container makes a good tail pipe pulse tool.
I've made all of the mentioned and had them work sucessfully all be it each
suited for their own individual purpose.


A
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3 years 10 months ago #40102 by Matt T

John Curtis wrote: I’ve noticed on some builds you don’t see all 4 cycles.


Those were probably 0-XXX gauge pressure transducers which output zero at atmospheric pressure. Called psig in English units.

What you need is a transducer that's for 0-XXX absolute pressure. 0 absolute is hard vacuum so it'll output a little under 15 psi of voltage at atmosphere. Easy math example a 0-5 v 0-150 psia transducer will output about 0.5v at atmospheric pressure.
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3 years 10 months ago #40110 by John Curtis

Dtech494 wrote: For the small investment it is worth trying and making your own transducer.
Some of them do not give the best transitions or resolutions. So it may be hit and miss. Often if you AC couple you get the best signal to display.
Input voltage and scaling on your display can also make a difference.
Some transducers are designed better for displaying rapidly changing pressures.
But if you make a harness and use that 3 pin connector (GM TPS ) style connector then you can easily swap them.
You will likely find having a 300 psi and 100 psi one to be useful.
The 100 psi one displays running compression better while a 200 or 300 psi one is better suited for cranking compression.
For vacuum waves a GM map sensor works excellent (with a 9v battery supply)
A GM fuel tank pressure sensor makes a good tail pipe pulse indicator (with a 4.5 volt battery supply.)
Or a peizo buzzer closed in a container makes a good tail pipe pulse tool.
I've made all of the mentioned and had them work sucessfully all be it each
suited for their own individual purpose.


A


This is very insightful!

Making Pressure Differential Sensors (PDA Sensors) for pressure pulse diagnostics.
Currently servicing Central Texas.

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3 years 9 months ago #40444 by juergen.scholl
To get a useful waveform the sensor's update rate will be paramount!

Although you might get specs on the sample rate in my experience more often than not these specs, especially from the cheap e-bay offers, are unrelated to reality and this will result in choppy, worthless captures. The result is hit and miss, I found one out of 4 tried sensors somehow useable...

To get good vacuum waveforms with absolute values you can employ a MAP sensor. This could be the sensor already on the engine or one you prepare to be used on engine that do not feature a MAP sensor originally.

This works fine if your scope allows you to zoom in on the crest portion of the waveform on top. If your scope can not do this then ac-coupling will allow you to get a waveform that will reflect relationship correctly.

An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.

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3 years 9 months ago #40456 by John Curtis
I actually decided to put the build on hold unless I can find a good quality sensor that matches the speed of the WPS500. I seen the specs on PICO website and I have been searching to try to find one that matches. I do like the idea of using a MAP sensor.

Making Pressure Differential Sensors (PDA Sensors) for pressure pulse diagnostics.
Currently servicing Central Texas.

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3 years 8 months ago #41432 by Paul Marchant
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