Why would you want a daily min/max graph?

Just to be clear and avoid any misunderstandings, the title is more about the point behind desiring

a daily min/max Graph.


A Brief History

In the past, the primary tool for monitoring fridge temperatures was the thermometer. Complicating matters, these fridges were often domestic ones with poor control and a tendency to drift. The perplexing temperature dial only added to the challenge. Given the unreliability of these fridges, it became crucial for staff to frequently check the temperature. Min/max thermometers provided a way to stay informed about any issues, even if one wasn’t present when they occurred.

However, in the event of a problem, the last thing anyone wanted was to use or sell compromised stock. Checking the temperature every 10 minutes wasn’t practical – it was time-consuming and addressed a problem that rarely arose. As a result, the solution was to check the minimum and maximum temperatures daily (or twice daily), with the “Strive for Five” principle emphasizing this practice, especially concerning vaccine storage. A daily min/max record was required because it was the best solution at the time.


There was, however, one positive aspect to the daily min/max report – the simplicity of having 28 to 31 readings on a single page, making it easy to review and comprehend. When everything was in order, as it typically should be, the daily min/max report served as the perfect demonstration of active monitoring. Yet, the min/max report proved entirely ineffective when issues arose. Consider a scenario where you restock your fridge every few days, and the temperature spikes to 12° daily but only for a brief 5 minutes. Although this doesn’t harm your stock, the min/max report would consistently display 12° each day, offering a misleading impression of a problem. A min/max report is only useful if the temperatures are within the required limits.


Regrettably, numerous procedures and requirements now hinge on the daily min/max recording. Temperature loggers effectively address the limitations of a daily min/max report. In the event of an issue, loggers provide crucial information, including the start and end times of the incident, the actual temperature extremes, and the duration at these extremes. This information is critical for determining whether stock needs disposal or if customers should be notified.

The drawback of temperature loggers is that printing all the data would result in numerous pages, which seems wasteful for something that may not be thoroughly reviewed.

There are two possible solutions:

  1. A daily min/max report: This is a great way of summarising the data, but you will have to return to the software to see what actually happened if something did go wrong.
  2. A graph.

From the descriptions provided earlier, the simplicity of a graph becomes evident. It encapsulates all the information in a fraction of a page, emphasizing the idea that a picture is worth more than a thousand words. This brings us back to the initial question – why opt for a daily min/max graph?

The desire is to distil the graph down to its bare essentials, focusing solely on the daily peaks and troughs. Yet, this approach leaves out crucial details like when these peaks and troughs started, their frequency, and whether there’s an underlying problem. Consequently, one still has to refer back to the data to grasp the complete picture. While the graph may appear visually appealing with two relatively smooth lines, it has lost 90% of its meaning. I would go so far as to say that without that 90%, the remaining 10% effectively becomes useless.

In essence, while a daily min/max graph may sound sophisticated and user-friendly, it essentially resembles a rusted vehicle with a fresh coat of paint. Let’s embrace the current era and leverage the simple, easy, and affordable technology available to us. It’s time to move away from unnecessary compromises.