Hello, I am having serious issues with temperature stability with my eVOLVER unit. During temperature calibration at room temperature per the wiki instructions, the water vials are not reaching an equilibrium temperature, and are continuing to slowly climb up to >27 C, despite all the heaters being turned off. This trend is confirmed by an external thermometer and has continued for almost 24 hours now. Can anyone please advise? Thanks in advance.
I replied to the email privately, but just including the response here incase others have the same issue:
I regret to hear that you’re dealing with some issues. More screenshots or information would be helpful for debugging. More is better. Here are some questions to help debug:
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Does the serial communications work? In other words, does it work when you start and stop stirring? Or actuate the pumps from the GUI?
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You said the temperature is climbing, to what? 50C? Or something lower? Does it stabilize? How does it behave if you set the temperature manually in the setup screen (not in the calibrations). This will tell me if there is feedback at all in the system or is there something wrong with the temperature sensors.
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what us the raw readings you see on the vials? Hit the RAW button on the setup screen to toggle to raw readings.
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Do you see the proper response? See below. If not, the signal isn’t going through:
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What is the room temperature of the lab? There is not active cooling on the sleeves so if the room temperature is high then the sleeves will be around that value.
Confirmed the communications are working. See screenshot above for raw readings.
I am not sure what the temperature is climbing to, only that it is steadily increasing by about 0.01 C every minute or so, as measured by an external thermometer. This has been continuing since yesterday so hypothetically the temperature could hit 50 C if we left it over the weekend, assuming the trend continues.
A further note: we have our eVOLVER setup inside a vinyl anaerobic chamber which has limited airflow. The ambient temperature in the chamber is currently 24.7 C, so the eVOLVER vials are still running considerably hotter than the environment. It could be, however, that the lack of external ventilation is sealing in the heat generated by the eVOLVER and causing the warming trend. Do you have any further suggestions?
Update: left it over the weekend and the temperature did eventually come down. It now seems to fluctuate around 25 C within about a 1.5 C margin, but in the short term it still does not reach an equilibrium (i.e. the reading changes by a tick every minute or so.) Ambient temperature in the chamber is stable so I am discounting external factors. I’m going to complete the calibration and report back on how it does at higher temp settings.
Update #2: Temperature instability is worse at higher temps. Despite leaving it overnight, the fluctuations are both faster and much wider, with the reading between 40-45 C and changing about every 10 seconds now. As such it is impossible to get a good calibration curve. Any further advice would me much appreciated.
OK update here. The temperature instability is the external reading, not the thermistor itself. The temperature reading was taken too close to the magnets. One tip was to tape the wire to the thermal couple so that it cant reach all the way to the bottom of the vial. Also, use more liquid (~e.g. 30 mL) in the vial so that the probe can sit farther away from the magnets. It would take longer for the temperature to reach equilibrium but should be ok since the liquid should be well mixed.
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