Temperature variation (w/MLX90632)

Hardware, PWM, and Optics
1

Hello everyone!

I’ve noticed some variation in the temperature of my Pioreactors (I’m using the Precision Temperature Upgrade Kit). It’s nothing extreme, but I find it a bit odd…especially since some of them do stay at the set temperature of 20°C.

I keep my Pioreactors inside an incubator at a constant temperature of 18°C. Is anyone else experiencing something similar, or does anyone have an idea of what might be causing this? It could be a simple issue I’m overlooking.

Thanks in advance!

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2

The calibration model uses the following variables to infer the temp:

  1. The inferred liquid volume (in ml)
  2. The temp sensor on the Pioreactor’s heater PCB
  3. The MLX IR sensor (the sensor that is looking at the glassware)
  4. The temp sensor on the MLX board (to measure ambient temp)

So if any of these are changing, that can cause the predicted temp to change slightly. For example. Are you using “Thermostat” or “Only measure temperature”?

Also, make sure you are using the correct orientation the MLX sensor. Our previous product photos had this backwards, but this is the correct orientation:

image
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(Note the position of the 6 gold holes on the PCB - should be on the left side when position correctly!)

3

Actually I misunderstood your question at first. You are referring to why there is inter-pioreactor variation. Again, looking at those variables:

  1. The inferred liquid volume (in ml) probably the same for all units
  2. The temp sensor on the Pioreactor’s heater PCB maybe different if using Thermostat
  3. The MLX IR sensor (the sensor that is looking at the glassware) maybe different
  4. The temp sensor on the MLX board (to measure ambient temp) probably the same for all units
  5. (Not mentioned previously): A constant bias term if the FIR temperature one-point bias trim calibration was done.

Do you perform 5. at all?

4

Actually there are two more variables!

  1. the model itself. To make the calibration model, we collected lots of data and temperature variations. We didn’t collection any in a 18C incubator, so you’re situation is slightly “out-of-distribution”. I think the lowest recorded temp was 20C.

  2. Organism activity: cultures generate heat in proportion to activity.

1 Like
5

Hi Cam! Thank you so much for all of this. I’ll check all those variables tomorrow, once I’m back in the lab, and report back. As usual… amazing tech support!!!

6

Update:

I had all of the 6 gold holes facing the wrong direction!

I guess this will fix the issue (I’ll keep you posted) :slight_smile:

Thanks!