Shock velocity logging problem

zhelinm
Posts: 1
Joined: Sun Jun 29, 2014 3:38 am

Shock velocity logging problem

Postby zhelinm » Sat Aug 09, 2014 9:37 am

Hi, have been trying to use the DL1 Mk1 to log shock displacement and using the maths channel to get the velocities. It seems that either I am having a lot of noise (wires to Penny Giles SLS130 series 100mm and Motec LPS 200mm) or the 12BIT ADC is creating this noise.

Logging is done at 100hz and with a 200mm Motec linear potentiometer for the rear shocks. The resolution I can get from the 12bit ADC is 0.0488mm. With each sample 0.01secs apart, I can potentially get a step velocity of 0.0488/0.01=4.88mm/s which is quite high in my opinion. I am getting this step velocity with vehicle at rest, so I am at a loss of what to make of the dynamic numbers.

I am trying to log the various velocities seen with different damping rates.

Is this an inherent problem that comes with the 12BIT ADC that we cannot do anything or is there some software walk around that we can use in Analysis 8.5?

I am considering upgrading to the Pro but with higher 1000hz, my problem will be amplified by 10x?

Could this be a sensor accuracy issue? Or could this be an internal voltage fluctuation issue? I am only using channel 1-4(5V) for the shock pots. Channel 5-7 are also fluctuating 0.04V every 0.01s with no sensors plugged in.

Plotting raw data with differentiation with time done, I am getting crazy spike velocities in excess of 3500mm/s. I am currently capping the maximum rate of change for raw data in order to limit the shock velocities to 600mm/s as a bandaid solution.

Anyone has any recommendations on how to resolve this issue? I am using the vehicle battery power which is not too stable itself.

1) Will the sensor be of any resolution concern? Penny Giles states that the SLS130 sensors have virtually infinite resolution.
2) Does the analog inputs fluctuate with no sensor connected? Is there a need to recalibrate? DL1 is on firmware v33 bootloader v5.
3) I am using the DL1 provided 5V and splitting it to all 4 channels. Is there a better way to do it?
4) The wires to the front 2 sensors are 2.5m and the rear wires are 4m long unshielded 3 core 20AWG wires. Is shielded wire required for this?
5) Any tricks within Analysis 8.5 to get some meaning data interpretation? I am tempted to use smoothing but it simply deducts away from the 100Hz sampling.
6) Does this mean 12BIT is not sufficient for shock velocities analysis?
7) Is there a need to use a separate 12V DC source to help in stabilizing voltages? I would assume the DL1 would have enough stabilization done internatlly on the 12V source?

Thanks in advance for any comments

Zach

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