Evaluating measurements

Thread Starter


Joined Jan 6, 2004
I programed a PIC 18F to generate pulses going from 120 to 6000 Hz.

Measured the output with two frequencimeters (ME and WA) plus the reading from an analog TRIO scope.

In the Excel file I listed following values:

PIC: frequency expected at the PIC's output.
WA: frequency values obtained with frequencimeter WA.
ME: frequency values obtained with frequencimeter ME.
TRIO: frequency calculated from the readings (which also listed).

Readings approximated to 0.25 of a division. Scope is analogic so I had to actually read the divisions in the mask.

On the right I listed the differences between PIC value and the three instruments.

The x axis of the graphic helds PIC values. The curves, the three differences above.

My conclusions, rather limited, besides that all my instruments are of poor quality:

a) PIC could be not producing the expected frequency. (But MPSIM, with current software, allows to think that I am getting the best of it with values close to the Hz in all cases).

b) I am very bad at reading my scope.

c) Frequencimeter ME is worst than WA. (Both frequencimeters are of the type embeded in garden variety multimeters).

Do you have more useful / educated conclusions to make? I will appreciate that.

Attached file here