Sensor Analysis Results Softpot Membrane potentiometer and AMS rotary sensor V:1.0

Reading this document This document contains information about the result of testing the Softpot Membrane potentiometer and AMS rotary sensors with the objective on using them in the 2014-2015 Omincoor project. The procedure we used to test them The results Conclusion

Softpot Membrane Potentiometer Test 1 Used a protractor and a multimeter to measure the resistance for different angles of pressure application. Test 2 The second time, I used the camera system to record the angle precisely while simultaneously recording the voltage drop across the potentiometer using MATLAB and an Arduino.

Test 1 Results and Data As for the linearity of the potentiometer, It is fairly good. But it simply isn’t practical when we put it in a time sensitive test.

Test 2 Results and Data These are the BEST results I got with the second test. The top plots are the potentiometer readings, the second ones are the camera system angle reading. As you can see, The readings are extremely unreliable.

AMS Rotary Sensor (AS50489) We tested this sensor with the help of the Tracking tools camera system and the chipKIT uC32 board. The communication between the sensor and the board was through SPI interface (Sketch include in GIT 9-Data Section). Then to been able to log the value on the PC we used a Matlab script to communicate with the uC32 via serial(Script include in GIT 9-Data Section). The digital angle calculation value of the rotary sensor was compared V.S the logs of the camera system, allowing us to test its resolution.

Results and Data Testing was done in a similar way to Test 2 for the membrane potentiometer. Using the camera system to measure precise angle while recording the corresponding reading from the sensor. Noise test – As seen to the right (sensor is red, camera is blue), the noise is comparable to the camera system noise.

Results and Data This is just one of many tests of tracking the angle reading of the sensor along with the camera reading data. As you can see, the curves are not exactly lined up ( I did my best to try and normalize them). This is due to the fact we had to start the camera recording and the matlab recording manually and therefore might not have started and stopped them at exactly the same time. But you can see that the reading from the sensor(in red) is fairly consistent with the changes in the camera readings. More plots on the next page..

Results and Data 10 degree decrements (camera sys. Glitching most likely lost view of trackable) 1 degree incraments

Conclusion The SoftPot Rotary Potentiometer is not a good sensor for our application. The AS5048A rotary sensor seems to have an acceptable resolution. The logs showed that it has a persistent noise close to +- 50 units (Error of ~ 0.3%) of its digital value output in steady state. If we are able to develop a digital filter, its utilization on the project could be considered.