Intellijel µScale 1.0 - Manual (Page 4)

APPENDIX A - CALIBRATION PROCEDURE
In order to accurately calibrate a µScale module you will need the following items:
• Digital Multi Meter (DMM) accurate to approximately +/-1mV and 4 significant digit display
(e.g. capable of displaying a value like ‘2.003V’)
• Variable voltage source preferably with an output range of 0-10V
• Small slotted screw driver for turning the trim pots.
Step 1: Measure the output of your voltage source with your DMM and tune it so that it is exactly 10V. You may also be fine with a
lower voltage (e.g. 5V) and use a source like the output of channel 2/3 on a Makenoise Math module or a Doepfer A138C with no inputs
patched in.
Step 2: Whatever known fixed voltage you have, patch it into the “IN” jack of µScale.
Step 3: On the µScale PCB you should see five separate trim pots as labelLED in the above photo. Look for the one labelLED “Scale
Input CV” and connect the ground probe of your DMM to pin 1 and the positive probe to pin 2. Adjust the trim pot until your DMM reads
exactly half of the input signal. (E.g. if your fixed voltage source was 10V, then the DMM should read 5V)
Step 4: With the voltage source still connected to the “IN” jack, make sure you have no note selected in the current scale. This will
result in the µScale outputting the equivalent of 0V on Output A and Output B jacks. Take a patch cable and plug it OUT A. Connect the
DMM to the other bare end of the patch cable so that the ground is attached to the shield and the positive lead to the cable tip. Adjust
the “TUNE A” trim pot until it reads 0.000V on the DMM.
Step 5: With the same connections as in Step 4, move the patch cable to OUT B and adjust the TUNE B trim pot until it reads 0.000V
Step 6: Move the patch cable back to OUTA and press note C (button #1) on the active scale. This will create a 1 note scale which
allows one to easily tune the octave width in 1V/Oct tuning. The DMM should now read somewhere close to the fixed voltage source (it
may be an octave below due to the SETTINGS menu settings related to shift and due to the jumper setting). Adjust “Width A” until it is
a whole number value (e.g. 10.000V).
Step 7: Move the patch cable to OUT B. Go to the INTRVL menu and choose a value of “1”. Since the scale is one note, the interval
value (if the SETTINGS menu---> MODE is IN-SCALE) represents the number of octaves above the fixed voltage that OUT B will be
(where every octave is 1V). So if your fixed voltage value was 5V, then an interval value of 1 would result in an output voltage of 6V on
OUT B (1 octave above 5V).
Again all you are mainly concerned with is tuning via TUNE B so that the output is a whole number value (e.g. 10.000V)
Step 8: You can test the outputs by changing the voltage reference value over the entire range. You should see both outputs jump in 1V
increments. You may see variations of +/-0.002mV at each stage due to non-linearity in the DAC and output amplifiers.