Plotting of QProcess output taking about 5 minutes to plot single value.

[d_stranz]

data_x and data_y in line 2 are local stack variables (I assume this is your class constructor) and have no relationship to the variables of the same name you use later.

In line 56, you increment x_position. I don't see anywhere where you reset its value, so once it reaches 60, it will continue to increase.

Otherwise, there doesn't appear to be anything in the code you have posted which would cause such delays. I would write a test program that strips out everything except the communication between your sensors and your monitoring program and see if that is where the trouble starts. No GUI, no writing to files, no plotting, just qDebug() statements to write what you receive to the console. And run it in the debugger, of course.