Q&A Forum
Hi Guys.
Having speed sensor stability issues, been battling this for a while. The sensor is in a Sun dyno, Hall sensor on correct wheel with 24 teeth. Sensor cable is shielded, connected at 'Your Dyno' end only. Latest firmware installed, running on RPM input 1 with correct number of teeth entered. Oscilloscope readings of the square wave input into 'Your Dyno' look good and are stable. Graphing the speed input during a run shows very erratic speed measurements, resulting in poor control of the electro brake. The erratic readings happen with or with out the brake on. Tested the cable - okay. Ran a new unshielded cable away from the chassis - same unstable result. Tried connecting the shielded cable to ground at both ends of the cable - one end to controller, other to chassis - this changed the square wave so it only pulled down 0.5V to approx 4V instead of all the way to 0V. Tried changing the software filter - only difference was when set to 10 the signal went away entirely.
Any ideas or suggestions would be appreciated.
Hi, do you have the original sensor and the original cable or something else?
Also, send a raw log file to me (jostein@yourdyno.com) and I can take a look.
Thanks for the reply Jostein. Sensor is a new GT101. Will get log file organised in the next few days.
I had a lot of similar issues with mine. Erratic speed signal and would not read anything over 3500rpm. I went through a couple of speed sensors and different trigger wheels.
What fixed mine was rubber mounting the Yourdyno.com box. I had it solid mounted to the control box I use which has some grounds for other sensors and things tied to it. Not sure how you have your's mounted or setup but that was an issue for me.
Thanks for the reply @james-meyers. I had read your post prior to asking. The controller we are dealing with is wall mounted beside the PC, approximately 3m from the chassis. The Hall sensor is however solid mounted to the chassis. Is this how yours is installed?
Hi Jostein, Raw log file attached.
Video of speed sensor behavior with vehicle at constant speed.
Yes, my speed sensor is solid mounted.
I checked the log, @madmartynz. The RPM signal is all over the place, I have never seen that pattern before.
Here are some ideas:
- Wrong dimensions on the trigger wheel
- Uneven distance between teeth. The trigger wheel needs to be perfectly even, and of course no missing teeth
- Too large distance between sensor and trigger wheel
- No or inadequate shielding of the RPM cable, too long cable
- Something wrong with the sensor
Cheers
Hi Jostein. Thanks for the reply. We have checked most of this already. What is the maximum length cable that can be run to the sensor?
Hi Jostein@admin
- Have tried 2 different trigger wheels, one 24 tooth and 1 triggered off the bolts on the end of the electro brake
- Tooth distance checked, both are even
- Distance between GT101 & wheels checked, 1-2mm as per spec
- Tried 2 different shielded cables and 1 unshielded cable
- Reduced the length of the cable down to 1m after relocating 'Your Dyno' controller.
Result still the same, unstable speed reading. I have 2 videos I will email to you with scope view of the GT101 input vs speed output - too large to attach here sorry.
Hi,
Yes, with that log file, it is not surprising that the readings are unstable. The raw data is full of noise.
You need a proper trigger wheel so the 24 tooth is the way to go (no missing teeth).
I suppose you have seen the need for a resistor on some earlier versions of the hardware box, see bottom of this page: brake/Roller RPM sensors - YourDyno.com
Your data does not really look like that is the problem though, the readings are generally following the correct RPM, but extremely noisy. You can try if you did not already.
1m cable length is of course very short. I have seen bit of noise at 10+ meters.
I can send you a YourDyno RPM sensor. If it fixes the problem then buy it, otherwise let's keep searching. First send me a picture of your trigger wheel setup.
Hi Jostein@admin. Pic of first trigger wheel attached. It is 24 teeth and is as per spec for the Honeywell Hall effect GT101 sensor. The cable to this sensor was 12m long, it went the length of the dyno, then up the wall to the controller. We relocated the sensor to trigger of a set of bolts (on the brake) on the opposite side of the dyno, moved the controller directly above it, and rewired it with a 1m cable. Same result, unstable speed signal. We then replaced the sensor with a brand new one. Same result, unstable speed signal. The fault is intermittent though, did you receive the second video I sent through?
Hi Jostein@admin. Managed to compress the 1st video file enough to upload. The run was immediately before the Dyno-run2 video. No setting changes were made, the sensor was not altered. The square wave on the PC oscilloscope below the 'Your Dyno' screen shows a stable and clean square wave input, same as dyno run 2 video. There is a step change in what the speed sensor is reading part way through the video, with no change to the square wave input. The square wave speed input is being measured at the terminals of the 'Your Dyno' controller.
Is there anything else we should be checking?