HV power supply - Characterization
Measuring the linearity of a power supply deserves its own post and they’re out there. In this case, I was only worried about how linear the mapping was from 10-20kV. With a well engineered supply like this, I confirmed that the linearity in the middle of the output range was a non-issue. This HaD Arksen post covers some of the other voltage spikes and ripples I checked for in my HV output. Luckily, any transient signals I was worried about were smoothed out by the control electronics inside.
The article also accurately describes the quality of the Arksen variable power supply I was using to set the control voltage from 0-10V. The most inaccurate link in my system was actually the display on the Arksen which was off by 10% at times! From then on, I always had a Multimeter in parallel to display the “true” input voltage
Syringe pump calibration
Before getting into fluid units, I followed the same process as calibrating a 3D printer axis to lock down the linear dimensions. I jogged the syringe pump 10 steps and measured the distance in mm. Took this measurement 3-5 times and updated the conversion factor already in the machine. Then I did the same with 50 step increments to refine the measurement.
Ideally when I jog a unit of one in my printer software, I would like it to be 1ml. This would make any flow-rate math simpler in the future. The easiest route was to measure the graduation markings on the syringe. It can be argued whether or not this is the most precise and accurate method but I told myself to worry about if it stopped me from producing fibers.
I could have tried something like extruding a volume of water and measuring its mass but I did not spend enough money on a scale to trust any gained accuracy. Disposable syringes have a rubber seal which can tend to be somewhat jerky (hysteresis) and this limits the precision I can hope to achieve. Glass on glass syringes are precision ground and what you use when you need smooth motion in your pump. I think they’re used to handle higher pressures for life science applications too?
In the end, it didn’t stop the show