Model for predicting temperature data of fridge

Question

I set up a sensor which measures temperature data every 3 seconds. I collected the data for 3 days and have 60.000 rows in my csv export. Now I would like to forecast the next few days. When looking at the data you can already see a "seasonality" which displays the fridges heating and cooling cycle so I guess it shouldn't be too difficult to predict. I am not really sure if my data is too granular and if I should do some kind of undersampling. I thought about using a seasonal ARIMA model but I am having difficulties with picking parameters. As the seasonality in the data is pretty obious is there maybe a model that fits better? Please bear with me I'm pretty new to machine learning.

Answer 1

When the goal is to forecast rising temperatures, you can forecast the lower and upper peaks, ie, their hight and distances. Assuming (simplified model) that the temperature change in between is linear we can, model each complete peak starting from a first lower peak of the temperature curve to the next upper peak down to next lower peak. So a complete peak can be seen as triangle which we easily integrate (calculate its area + the area of the rectangle below of it). The estimation can now be done by a integrating a number of complete peaks we have already measured. By repeating this procedure, we can do now a linear regression on the average temperatures and alert when the slope is above a defined threshold.

As this only tackles a certain kind of errors, one can do the same for the average distances between the upper peaks and the also for the lower peaks. Ie, take the times between them for a certain periode, fit a curve (linear regression can possibly be sufficient) and alert when the slope of the curve is indicating too long distances.

Answer 2

It's mission impossible. If fridge work without interference, then graph always looks the same. The change can be caused, for example, by opening a door, a breakdown, a major change in external conditions. But you cannot predict such events. Instead, you can try to warn about the possibility of problems in the near future, for example, based on a constant increase in average temperature. This situation may indicate a leak in the cooling system. By the way, have you considered logging the temperature every 3 seconds? This is usually unjustified, because it is physically impossible for the temperature to change to a measurable degree in such an interval. Our team usually sets the login interval to 30 or 60 seconds in such cases. Sometimes even more. Depending on the size of the chamber, the way the air is circulated, the ratio of volume to power of the refrigeration unit, etc.