Why and How - Monitoring and Recording Temperature
We need to know the temperature! Whether we are monitoring our walk-in cooler, freezer, refrigerated truck, or the growing areas – we always need to watch the temperature for deviation from the range we have defined as optimal. Recording those observations can be a requirement for Food Safety compliance, and it can be advantageous to know the history – just like we benefit from knowing the history of the weather.
Measuring Temperature
There can be many ways of measuring temperature, such as a thermometer and an old-time mercury glass thermometer. Our preference is now for a calibrated mercury glass thermometer from the National Institute of standards, a digital readout, or an infrared sensor probe connected to an electronic device so that we can digitize, record, graph, and archive that data.
I want to avoid carrying around a glass tube of mercury and a pad of paper and write down temperatures all day. I wouldn’t even want to be doing that if it was an electronic device taking the temperature. I still had to write it down. However, I’m happy to spend some time putting in an electronic device and a system to read it, analyze it, and then notify me in some way or another if things are out of bounds. I will set those bounds so that any outlier cold or too-hot situation will issue an alert via text or email. If I notice a no temperatures are being read and recorded, the batteries might be dead, or the device has failed – it is time to investigate! This is the whole point of what we are doing, measure – analyze – take corrective actions.
This is known as the DMAIC approach it is used to optimize their existing systems and continuously implement improvement with greater accuracy as time goes on. The term DMAIC stands for Define, Measure, Analyze, Improve, and Control. Make a note card and carry it around with you to remind you to constantly:
- Define
- Measure
- Analyze
- Improve
- Control
Graphical analysis can give a quick visualization, and my human ability to recognize patterns can be fast and more manageable than writing a bunch of AI rules. So, I’m happy to do that extra work building this system so that day in and day out – even when I’m sleeping – even when I’m not on the facility campus, all temperatures are being taken, they’re being recorded, and they’re being archived.
I can look at a graph of them and gain some insights almost instantly, and I didn’t have to carry the pad of paper around, write them all down, and enter them into some database because I don’t have time to do all that. So we’re going to go over some fun “measurement toys” that I found. There are a range of devices; some of them are expensive some of them are calibrated. Calibrated is necessary if you’re going to use them for any sort of regulated requirement in the Food Safety Modernization Act (FSMA) or the Produce Safety Rule that requires or “says you must” record temperatures. In most cases, you need a traceable thermometer to a standard and a calibration procedure. So you’ll also have to maintain data and records on that calibration.
A Real World Example: Temperature alert and Graphical Analysis at 4am
I know it might not be good healthy sleep practice – BUT I do have my cell phone next to my bed at night, and I have temperature monitors connected to that phone. At about 03:00, I notice that the tomato greenhouse is showing 39F in red – the alert.
I go to investigate. None of the 3 heating systems is functioning; in fact, one LP gas heater is in a loop of purging, trying to fire, and purging again, which is actually filling the greenhouse with the unconditioned outside air!
I investigate the LP gas tank outside which is empty with a thick skin of ice on the bottom 10% of the tank. A call to the propane supplier after hours to report an outage – we are supposed to be on autofill!
I’ll have to shut down all the LP equipment for safety and stop the purging and misfiring cycling. I will get some backup heat working and wait for the delivery. I’ll have to restart systems after the delivery and purge any air in the LP lines after the system stabilizes from the outage and refill.
While waiting I’ll investigate further and download some temperature data to see if the last few day’s temperature histories lend some insight.
Analyze
There is a clear loss of temperature control and it has been developing over a few days!
We can see the night before, the system failed to control temperature just before sunrise – so we had an advance warning but missed it. Further, you can see graphically on this trouble alert night the system started failing to regulate temperature and went into an uncontrolled drop as all heating systems shut down. The upturn at the end was the manual restart of the oil heating system and then the return of LP gas heat when the tank got filled, and the heating systems were restarted.
The daily pattern of temperature and daily solar gain with a corresponding drop in humidity with solar gain and venting is rapidly recognizable, as well as the abnormal pattern of the sudden fall of temperature and the lack of the wider temperature line of the heaters cycling on and off. So congratulations! You just visually outperformed the rudimentary AI of our purchased temperature alert system. We should give you the job! We can do just that by creating visual dashboards where our system performance is constantly visible, and we can tell at a glance if something is a miss. That will be another project The Improve phase – but for now, let’s look at how to install these devices and download data and use spreadsheets and charts
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Temperature & Humidity WiFi Sensor pod
We have tried many sensors and temperature monitors, and we have so many in our sensor “graveyard” that didn’t hold up, or the battery is not easily replaceable, or just were not reliable.
These Govee sensors have been an affordable reliable and dependable sensor pod we have in every building and greenhouse. They even come with a 2-year data storage cloud hosted in the US; they are made in China.
Once activated and connected to our WiFi, the apps for android and iPad will give us a glance at current conditions and access to download data. The desktop login will provide us with full access to all the device settings including calibration.
