MEAM.Design - MEAM 247 - P3: Stirling - Testing Procedure & Data Format

Testing Procedure

1. Open RealTerm (Start > Programs > GM Lab Software).

2. Make sure USB cable is connected to computer.

3. Connect battery and check for GREEN power LED.

4. Select ‘Port’ tab.

5. Change ‘Baud’ to 9600.

6. Change ‘Port’ to 7.

7. Select ‘Capture’ tab.

8. Specify an output file.

9. Click ‘Start Overwrite’ open output file.

10. Select ‘Send’ tab.

11. With engine running send any number to request data (RED Led will be lit while data is sending).

12. Click ‘Stop Overwrite’ to close output file.

13. Verify transmission was successful by checking for an RPM at the end of the output file.



Output Format

<time-stamp 1>, <angular position 1>, <pressure 1>, <temp hot 1>, <temp cold 1>
…
…
Repeated for 10 revolutions of flywheel
Output rate of approximately 2 kHz
…
…
<time-stamp n>, <angular position n>, <pressure n>, <temp hot n>, <temp cold n>
RPM: <measured rpm>



Data Details

NOTE: ALL VALUES ARE GIVEN IN HEXADECIMAL

<time-stamp> Each time unit is 256 μs
<temp hot>, <temp cold> 0 – 1023 correspond linearly to the measured voltage between 0 and 50 mV

See the thermocouple reference sheet for voltage output to temperature conversion.

<pressure> 0 – 1023 correspond to the measured pressure between 0 psi and 50 psi
<angular position> 0 – 1023 correspond to the angular position of the flywheel between 0˚ and 359˚. At 0˚ the Piston is at Bottom Dead Center.



Matlab Hints

The function hex2dec converts hexadecimal values to decimal.

The function textscan may be useful for automatically parsing the log files. Note however that you will want to delete the RPM line at the end of the file to make the format consistent throughout the file.

For example, Libert has provided us with this helpful code:

fid = fopen(test_file_name); %open file
data = textscan(fid,'%s %s %s %s %s','Delimiter',','); %scan text into 5 columns of data
fclose(fid); %close file
t = hex2dec(data{1,1})
pos = hex2dec(data{1,2})
pres = hex2dec(data{1,3})
temp_h_mv = hex2dec(data{1,4})
temp_c_mv = hex2dec(data{1,5})