Automotive Weekly Waveform #7 - Variable Reluctance (VR) Sensors
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- čas přidán 5. 08. 2024
- Let's grab a variable reluctance sensor signal waveform this week. This are most commonly use as crankshaft sensors but can also be found in camshaft positions sensors, transmission speed sensors and vehicle speed sensors.
Variable reluctance sensors are normally a two (2) wire sensor and they produce an AC sinewave signal. Some sensors have a floating ground or have a bias resistor and the sinewave will be centered between 1-2 volts and other sensors have the sensor ground connected to the engine and they will be centered at zero (0) volts.
Cranking amplitude should normally be between 800mV and 1.2v and idle amplitude will normally be between 10-20v. The amplitude can exceed 50 volts if the engine speed is increased.
The best signal can be gained by connecting the scope between the sensor's + and - terminals but if you scoping multiple items on a scope with a shared ground the connect the scope ground the battery- or the engine and then connect you scope channel lead to the sensor's + terminal.
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EXCELLENT , EXCELLENT , EXCELLENT,,,,,,,,,, I AM MAKING UP A USB FLASH DRIVE WITH ALL OF THESE EXCELLENT TESTS.
Let me know when it’s done buddy.
as a relatively new picoscope user I've taken the liberty when I do maintenance/repairs on cars to take 20 minutes to gather known good waveforms. I actually tell my customers that I'm doing this for their benefit so that if (when?) their car comes back I've got data to utilize. I haven't had 1 person say don't do this, but I do always ask. I'll be honest the first few times gathering data took way longer than I wanted but after a few it becomes easier of course. Practice makes perfect here and now I've got lots of stored waveforms for cars I work on. I think of these captures like just getting a new tool for the box. It's an investment.
That is the perfect mindset to have.
Looking forward to this weeks assignment.
Awesome. Can’t wait to get to work!
THANK YOU SIR , SIMPLY AMAZING !!!!!!!
Thank u sir👍
QUESTION: Are the “teeth” on the spinning cam magnetized? This may be why the waveform looks like it does.
Most, if not all, VR sensors do not use a magnetized cam trigger wheel. The magnet is in the sensor and the magnetic field flexes and the steel trigger wheel passes by. This flexing field in what induces the voltage into the coil of wire wrapped around the magnet inside the sensor.
Many of the 3 wire Hall effect sensors is a magnetic trigger wheel.
@@ThePracticalMechanic Thanks for the quick reply!! Good to know.
Hi.., i found my car after long off, CKP signal at N1+/- pin in ECU only 1.5VAC on started, engine crank but won't start, no fire on spark plug, also the pin of rpm meter no rise move at all... unless i reset the ECU (release batt or EFI Fuse), the CKP signal on N1 is 3.3VC on started, and the car will start and run normally without any problem... and will happened again after long off the engine, i already replace the CKP sensor and batteries with the new one, but it is not solving the problem.... any advise will really appriciated, thank you.
i have very few foreign cars what american cars usually have 2 wire. also can the older like chevy with points and condensor be captured on scope and tell dwell time thanks
I believe the 2 wire wss on chevys are sine wave
@@Baitmakerz yea the two wire wheel speed sensors are vr sensors. Many of the ford truck crankshaft position sensors are also VR sensors.
Where is a decent place to get known good waveforms? I know pick has a library but I can't install picoauto so no access to their library. And is it necessary to unplug the vvt solenoid when testing cam sensors?
There are several places to get known good waveforms. You should slowly build your own library, join a Facebook group that is specific for known good waveforms, diagnostic network and iATN are all great places for known good waveforms.
When testing camshaft sensors I don’t unplug the VVT solenoids. I only unplug them if I am performing a correlation test and the known good waveform is noted for that test condition.
@@ThePracticalMechanic ok that makes sense, I had a tech tell me to always unplug the vvt and I wondered about it for awhile. So thanks for that.