Temperature Control Limitations/Expectations

[KarstenSkogs]

Continuing the discussion from Pioreactor 40ml released!:

@sharknaro

Hi @KarstenSkogs,

In our experiments, we have been diluting 2-12 mL cold reagent. However, we never experienced long response time, in fact it was immediate in most of our experiments. One question I had in mind is whether you tried to modify the config.ini Kp parameters at the [temperature_automation.thermostat] and if you did, how was your experience?

In our case, modulation of the Kp parameters was a successful solution to modulate the response time.

Hi @sharknaro, I have moved this topic into a new thread to avoid hijacking things too much.

I did play around with the PID parameters, and it certainly helped move the heating output to 100% more quickly, but the issue was more about the total time between a temperature perturbation and the return of the temperature to the target (within a tolerance). I think the most standard term is settling time. This delay is a function of both the aggressiveness of the temperature control loop and the physical properties of the system, like the power the heater can dump into the vial at 100% output and the size of the perturbation.

I’m not entirely sure what to expect from the pioreactor on this front, so I’ve probably missed some documentation on the topic.

For instance, here, it takes almost an hour to move from ~28C to the target of 37C. Perhaps I messed up the installation of the heater or perhaps this is somewhat expected performance.

To more closely match our scale-up targets, I have also been attempting the aerate the pioreactor at around 10-30 vessel volumes per minute, and if this air is dry and at ambient temperatures, the heating output to maintain the target temperature can be close to 90-95% (and it is sometimes impossible). Under these circumstances, the addition of some cold reagent can lead to a long perturbation away from the target temperature.

To be clear, I don’t know if what I’m describing is normal, but at the time that I was chasing down the issue, I figured I was just asking a bit much from the system.

I made some prototype systems to preheat and humidify the input air, and that seemed to help a good deal, if anyone is in a similar situation, but if anyone has any advice, I’d really appreciate it.

[sharknaro]

Hi again @KarstenSkogs,

From what I can see, you’ve delved much deeper than I have. Although I do not have a clear answer to your question, I can give my response to some of the questions you asked.

@KarstenSkogs

it takes almost an hour to move from ~28C to the target of 37C

In our side, we heat generally from ~24C to 30C which takes ~0.5 hours. Hence, I do not think you messed up with the heater installation.

@KarstenSkogs

Under these circumstances, the addition of some cold reagent can lead to a long perturbation away from the target temperature.

I understand your struggle better now. What some of us are doing is to control the temperature of the environment by placing the pioreactors into the incubator. If this option is possible, it can help to reduce your settling time.