AnalogX for Shock Load Measurement

[DougK]

I'm trying to connect an AnalogX to measure the load on each corner using shock load donuts. On the workbench I connected the AnalogX to a RaceCapture Pro2 and connected a load cell amp to the AnalogX analog input 1 (blue wire). I have a voltmeter on the load cell amp output and it reads a steady 0.09V with no load and goes up when I lean on the load cell. However, when I watch the CAN channel in RaceCapture it varies a lot and does not track the input voltage.
Here is my setup in RaceCapture:
Can Bus: On
Can ID: 935444, offset 0, length 2, unsigned, mask 0, little endian, non-bitmode, 10 Hz
Formula: *1.0 / 1.0 -0.09
I set the precision to 2 with a min/max of 0/5 V.
I'm seeing values of 40 to 200, and no correlation to what is happening at the input. This is above the max value of 5V also.

Any ideas on what I should look at next?

Thanks!

Doug

[DougK]

I decided I was making this too complicated to start out, so I removed the load cell and load cell amp and replaced them with a potentiometer connected between the 5V and ground on the analog input side of the AnalogX, with the wiper going to the channel 1 input. I put a voltmeter on the pot and was able to watch the voltage go from 0.00 to 5.05 volts as I adjusted it. I set it at 4.12 volts on my voltmeter and left it there.

I changed the formula in RaceCapture to be x 1.0 / 1000 + 0.0 because I realized the units the AnalogX was sending were millivolts.

With the voltage at the input a steady 4.12 volts I could watch the RaceCapture channel vary from 3.07 volts up to 4.34 and back down, somewhat randomly, but it would not hold steady. Suspecting noise I put an oscilloscope on the input signal - it was clean.

Still struggling with this... anyone have any ideas?

Doug

[brentp]

Hi Doug, is this related to the other topic where you suspect the data offset was wrong? Is this still an issue?

[DougK]

Brent,

I think this issue is related to the other one I posted about the input order being reversed. When I changed the input offset (or when I changed which analog wire I connected my input to) the data displayed in RaceCapture tracked that on my voltmeter much more closely. That said, there is another issue I opened under the bug report section of RaceCapture - I cannot select offsets greater than 5 from the CAN channel mapping menu - they are off the bottom of the dialog , not visible, and cannot be made selectable. So, this particular issue about shock load should probably be replaced with the other ones.

Doug

[brentp]

Thanks, it's what I figured. I see you also resolved the CAN mapping issue in the other thread, too.