A small 24 V centrifugal pump moves the water in the JOBO CPE2 bath. Five-probe logs before and after: heating speed barely changed, the bottles ran close together, and the bath now shows the thermostat’s on/off cycles.
The JOBO CPE2 produced locally steady readings, but different locations did not converge. The transfer test adds the process question: warm liquid entered the rotating drum, then its measured temperature fell. What this means for preheat, circulation, and Panterla’s readiness criteria.
A note on the name. “Panterla One” is the working name for this automatic film developing machine — nothing is finalized yet, but it’s the name used for the project going forward in these engineering logs. Summary. I tested direct heating as a replacement for the traditional water bath in the Panterla automatic film development machine. The prototype used a 24 V / 150 W immersion heater, approximately 500 ml of water, active circulation, a digital temperature probe, and closed-loop temperature control. The measured linear heating rate was 3.59°C/min, corresponding to an extrapolated 20→38°C heat-up time of 5.02 minutes. During a separate steady-state test, the recorded temperature had a standard deviation of only 0.033°C over the analyzed four-minute window. The experiment also exposed a separate problem: the control probe and external logger disagreed by about 0.3°C, showing why stability and absolute accuracy must be treated as two different engineering problems. ...
Precise temperature control is one of the hardest engineering problems in an automatic film developing machine. This experiment used 38°C as its reference, but the working temperature and tolerance must come from the selected chemistry’s instructions. For an autonomous machine, I needed to compare how quickly each heating approach brought the liquid toward that reference and how much its recorded temperature varied afterward. I compared five heating approaches in six configurations, including runs with and without active stirring. These are the original results; the later processor experiments linked below add process-container and transfer measurements rather than replacing this dataset. ...