Temperature Probe

Readings are taken with hand-held spear-type thermometers pushed into accessible parts of the bulk, or, in a more permanent installation, with thermocouple or thermistor sensors mounted at intervals along cables suspended through the bulk and connected to a logging system. Either way, the instrument measures temperature at a point, and only at that point — it has no mechanism for sensing mould growth, insect activity, or anything else directly.

Because heat has to be generated, accumulate, and then conduct outward through poorly conductive grain before it reaches a sensor, a temperature rise is necessarily a delayed signal. By the time it registers, the underlying activity — fungal growth, insect feeding, or elevated respiration — has already been under way, and whatever damage that activity does is already largely done by the time the trend becomes visible on a log. Temperature monitoring is therefore better understood as a way of tracking the history and progression of a problem than as an early-warning system that catches trouble before it starts.

This has a direct consequence for what a falling or cooled reading means: it indicates that biological activity has slowed, not that the deterioration already caused has been undone. Mycotoxin that formed while the grain was warm does not disappear when the bulk is subsequently cooled or aerated, and insects killed by a cooling or fumigation intervention still leave behind every kernel they damaged before they died.

A rise in temperature can come from several unrelated sources: the grain's own respiration, active fungal or insect metabolism, solar heating conducted in through a bin wall, warm grain that was placed into store without first being cooled, or currents of moisture migrating within the bulk that carry heat with them. A temperature probe cannot distinguish between any of these causes from the reading alone — a rise is a prompt to investigate the bulk further, not a diagnosis of what is causing it.

What a sensor system can detect is entirely bounded by where its sensors are. Cable spacing and position through the bulk determine what is and is not within range of detection, and the fines-rich core that commonly forms beneath a fill spout — precisely where spoilage tends to start first — is not guaranteed to be where a given installation's sensors happen to sit. Effective monitoring depends on placement decisions made when the system was installed as much as on the sensors themselves.

Temperature monitoring complements moisture management rather than substituting for it. A lot binned too wet for its intended storage duration can still deteriorate even while reading cool, because moisture, not temperature, is the underlying driver of mould growth and storage risk; a cool reading on a wet lot is reassuring in appearance only. Effective stored-grain surveillance treats temperature and moisture as separate, complementary signals rather than relying on either alone.