calibration

Rocketlogger Calibration Information

Requirements

• One Keithley 2450 SMU
• Two SMU probe cables
• RocketLogger test leads

Process

1. Select the 'Calibration Measurement' option in the web interface
2. Capture the following sweeps with the RocketLogger: Voltages, Current Low 1, Current Low 2, Current High (both)
   • General SMU settings:
     • Two wire measurement
     • Voltages:
       • Source Voltage and Measure Current
       • Voltage Range: Auto
     • Currents:
       • Source Current and Measure Voltage
       • Voltage Range: 2 V (fixed)
       • Current Range: Auto
   • Sweep Settings (Menu -> Source -> Sweep)
     • Type: Linear Dual
     • Definition: Points
     • Points: 101
     • Source Ranging: Auto
     • Source Delay: 250 ms
     • Once all the settings have been input (see also below), press generate, go to home and press trigger to start the sweep
   • Channels:
     • Voltages (all V channels at same time):
       • Select all V channels
       • Sweep: -5 V -> 5 V -> -5 V
     • Currents:
       • Source Limit: 2V
       • High (both I channels at same time):
         • Sweep: -100‌ mA -> 100 mA -> -100mA (the 1A range of the SMU is not too great, so we don't use it)
         • Force High Range on the RocketLogger
       • Low (both I channels separate):
         • Sweep: -1 mA -> 1 mA -> -1 mA
3. Perform the calibration in Matlab (see rl_do_cal.m)
   • Set the correct files in rl_do_cal
   • rl_do_cal(0) (set create_plots to 1 to plot the residuals and pareto optimal error figures)
   • Copy calibration.dat to /etc/rocketlogger on the BeagleBone (via the /home/rocketlogger directory)
   • Calibration file format [TBD]

Hints

• Before triggering the sweep, SMU output has to be on (to avoid noise on the measurement). There should also be a step between the initial measurement and the first calibration level -> set the SMU output to 0 before triggering.
  • Alternatively you can start a sweep and then push the ON/OFF button twice to stop at another level.
• The Matlab script tries to detect the weird peaks caused by the SMU ranging, they should not cause any problems.