Thread: Discussion G sensor not reading correctly
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Old Jan 23, 2013, 09:11 PM
BobW99 is offline
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Thanks for the reply Bill.

OK I downloaded the Beta 10.43 and updated the V4 and g sensor firmware.

The Zaxis value is now reading .92 g now which is better. Would the g sensor firmware update have something to do with that or is it just sensor drift?

I tried the min/max RPM limiting and it works well in bench testing. Hopefully it will work well on track where the current draws are much higher. On track is where I have been having the problems. The RPM reported in Live model is 13500 RPM which is correct for the motor I am using.

When a log file is saved and then reloaded the g readings are still not there. The program doesn’t seem to be writing them to the .cdr file.

In one of the next updates I would like to see the Zaxis values available for display as well. Currently Zaxis cannot be selected in graphing module.

The optical sensor is still not reading correctly. Also the only way I can get the Speed calibration to accept new values is to close the program and restart it. If I make a change to the speed calibration parameters and just download the data from the recorder again the RPM and speed data is unchanged. Also the sample rate used to convert RPM to speed is different that the recorder data rate. I am using 50 hz sample rate and the graphed speed data looks like it is converted at 10 hz or less. I can send you a screen capture if you like.

To try and figure out what is going on with the optical sensor I downloaded the same data file from the recorder while changing the sensor position. The sensor is actually mounted on the drive shaft which rotates at spur gear speed.

The values used on the calibration sheet are as follows Spur = 75, Pinion = 46, Gearbox = 2.5, Tire dia = 2.48 in. The motor Kv=1850 and battery voltage = 7.5V. (approx motor RPM = 7.5x1800 = 13875 RPM)

First test - Sensor on pinion/motor Reported Motor RPM = 8447
Since no correction should be applied to the RPM this should be the actual RPM of the drive shaft where the sensor is mounted. The drive shaft speed should be around 13875 * 46/75 = 8510 RPM so the reported value looks good. Assuming this number is correct the second test was to change the sensor position on the calibration sheet to the actual sensor position on the spur.

Second Test - Sensor on Spur Reported Motor RPM = 5181
Using the 8447 RPM from the first test as the shaft speed the Motor RPM would be 8447 *75/46 = 13772 RPM. It appears the program uses 8447 * 46/75 =5181. So the pinion/spur ratio is inverted from what it should be.

Last question. I have an old hall effect sensor from a CDR V1 I bought 10 years ago. Will it work with the V4 logger? This method used to work fine so I think I will try it if the optical sensor won’t work.

Hope this makes sense.
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