Magnetic transducer for engine rpm on Cat diesel 3126

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Redmech
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Posts: 7
Joined: Wed Sep 07, 2022 3:08 am

Magnetic transducer for engine rpm on Cat diesel 3126

Post by Redmech »

Hi,

I have had my 4425A for a bit over a year, I have used it with great results for several different jobs. I'm going to try and attach a waveform I recorded. This waveform was taken on a Caterpillar 3126 HEUI engine. I have a magnetic transducer that is in flywheel housing, it would be reading solid metal until the hole that is used to pin the engine on cylinder #1 or #6 top dead center comes around once every revolution.

I have a couple WPS600C pressure transducers I plan to use on off road heavy mining equipment ordered. Once I have one I'd like to use the flywheel pickup on one channel, pressure transducer measuring engine oil that actuates hydraulic injectors, a channel to measure voltage to injector and that sort of thing, may also use pulse sensors in the intake, maybe measure injection actuation voltage to solenoid that controls high pressure engine oil pump (HEUI).

My quetion, how do I turn the info in this recording into easy to read engine rpm for in the future when checking other inputs? I took Adam Robertson's Pico course earlier this year at Vision KC, and will be taking more training at VisionKC next February/March 2024.

I work on a lot of Cat machines and once I get this figured out I will use the same process on many many other cat machines for many different tests.

I've read around on the math channel is cool thread a bit, trying to process this all. Every spike that the pico reads should be one engine revolution, and it is at TDC.

When I tried uploading file, it said attachment was too large, hopefully I get this figured out.

Thanks for any help everyone!!

ben.martins
Pico Staff Member
Pico Staff Member
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Joined: Tue May 16, 2017 1:02 pm

Re: Magnetic transducer for engine rpm on Cat diesel 3126

Post by ben.martins »

Hi Redmech,

Great to hear success stories with Pico in non-automotive industries. We know it would work but always nice to hear the win's!

It doesn't look like your waveform has uploaded. We have had some problems with attachments on the forum but they should be sorted now. Is it possible to try and upload again as it would be great to see the waveform. If not, can you upload to the waveform library?

The waveform you mention from the CAT HEUI engine is very similar to ones I have captured when supporting a customer for a 962H intermittent non start. We were looking at the timing sensors, injector current, IAP and fuel pressure.

You should be able to graph the crank sensor speed changes using the CRANK math function. We will be able to help more once we have the waveform. If it's saying it's too big can you save just the one buffer, Save current, and then try uploading again? Crank and frequency maths are those math channels which are really helpful especially when dealing with subtle misfires which don't register as a fault code but can cause power issues as seen here - https://www.picoauto.com/library/case-s ... ic-process.

Good to have you with us and if I have any CAT issues I know who to reach out too!

Kind regards

Ben

Redmech
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Posts: 7
Joined: Wed Sep 07, 2022 3:08 am

Re: Magnetic transducer for engine rpm on Cat diesel 3126

Post by Redmech »

Thought I would add couple screenshots of my first time using WPS600C pressure transducers checking hydraulic pressure reliefs of an implement pump on a Cat D11R carry dozer that has 63,000 hours on it. pretty amazing tool.
Attachments
Image 12-6-23 at 7.55 PM.jpeg
Image 12-6-23 at 7.57 PM.jpeg

ben.martins
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Pico Staff Member
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Joined: Tue May 16, 2017 1:02 pm

Re: Magnetic transducer for engine rpm on Cat diesel 3126

Post by ben.martins »

Great capture Redmech, thanks for sharing!

WPS600C is great isn't it! Adding a little filtering here will help clean that signal and you should start seeing the pulsations within the system. You should have nice even pulses based on the output of the pump. If you use the time rulers you can even work out the pump speed by the number of pulses.

One thing that stands out is the difference in amplitude between the main section and implement section. Is one pump louder than the other?

If possible I like to grab the engine speed at the same time as hydraulic measurements as this repeating the test next service can show whether the engine speed is changing with hydraulic load. The setup for this is already in the HD/OH guided tests with PicoScope 7 Automotive and we talk through it here on YouTube https://youtu.be/xcIKdkkLTqg?si=oM-Ai7eyxsFdQ9zA&t=225.

Given the sample rate and the timebase, I imagine this is quite a large file otherwise it would be a great one for the waveform library!

Thanks again for sharing.

Kind regards

Ben

Redmech
Newbie
Posts: 7
Joined: Wed Sep 07, 2022 3:08 am

Re: Magnetic transducer for engine rpm on Cat diesel 3126

Post by Redmech »

This particular pump is a two section gear pump. This machine has had an issue of cracking a fitting about once a week for the last 4-5 weeks, a -16 ORFS elbow, that sees 3,600 psi oil from the tilt section of the pump (channel 2). Depending on what functions the dozer does, when the blade is tilted rearward, the control valve uses oil from both sections, that is the first zoomed picture. I thought my zoomed in up and down pressure was the relief doing its job. Would filtering help this?

I have purchased the pico optical pickup that I will use for engine speed, or maybe tie into a speed sensor, the optical pickup is quick to setup, but not as informative as say flywheel ring gear, this is a production coal mine and I try to keep machines moving.

Pico is allowing me to do better Diag without having to be so intrusive. Just got get it figured out and hone skills.

Thank you Ben for the info. I’ll go do some looking at the guided test for this.

ben.martins
Pico Staff Member
Pico Staff Member
Posts: 534
Joined: Tue May 16, 2017 1:02 pm

Re: Magnetic transducer for engine rpm on Cat diesel 3126

Post by ben.martins »

Thanks for filling in pump details. I've seen this dual pump setup where both pumps can assist in a service. I'm sure Doosan/Develon use a similar technique in their excavators.

Filtering will just help remove some of those unnecessary frequencies. Please remember though to capture without filtering active, sometimes noise is useful!

The optical pick up is really helpful for getting that speed signal but as you say, a dedicated engine speed sensor will have more pulses per revolution which equals more resolution. Given the environment you find yourself in though speed and being as non intrusive as possible is key so the optical pick up will give you valuable information without being intrusive.

We're all hear to help so please don't feel you're alone. If you want any advice please use the forum and ask away! Alternatively, you can always contact support@picotech.com.

Kind regards

Ben

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