Sensing is a general term that applies to the use of sensors to detect something and convert that data into a signal that can be read by an observer or an instrument.
A thermometer is a sensor that measures temperature. It has a liquid that expands or contracts in a tube with gradations on it that can be observed visually. Such a sensor is not useful for automatic systems.
The TGM System employs the following sensors that can be read automatically along with a GPS Receiver:
|Temperature (T)||Relative Humidity (RH)||Barometric Pressure (BP)|
|Static Pressure (SP)||Luminance||+ GPS Receiver for location and time synchronization|
Ideally sensors should not influence what they sense. Barometric, static pressure and luminance sensors do not effect what they are sensing.
A barometric sensor is called an absolute sensor because it is measuring the pressure created by the atmosphere against a vacuum (or 0) which never changes. A static pressure sensor is a differential sensor because it measures the difference between two volumes of gas — the outside atmosphere and the higher pressure (or lower in a negative system) created by the resistance of the grain mass when a fan is operating.
Temperature sensors are relatively inexpensive and reliable but present a challenge regarding location. They are easily influenced by sun, other heat or cold sources, and can be expensive to locate properly — in order to be the most useful to manage grain aeration.
Relative Humidity sensors are the most expensive and historically have been the least reliable of the sensors useful to grain storage. The issue of location applies the same as to temperature sensors. In addition most RH sensors use capacitance or resistance changes in the sensing element to interpolate a corresponding RH reading. These types of sensors degrade over time because electricity flows through the sensing element, are not full range and are prone to condensation problems.
Laboratory type instruments are expensive and will not survive grain storage applications.
The TGM Micro-Beam™ relative humidity sensor
TGM utilizes a proprietary relative humidity sensor that is full range, does not degrade over time (no electricity flows through the sensing element) and survives condensation.
This sensor uses Micro-beam technology.
The ruggedness of this sensor is borne out by being qualified for use in the CERN particle accelerator near Zurich Switzerland.
Grain storage bins do not have radiation issues like the tunnel at CERN but a long life of dependable service can be expected from a design that incorporates these attributes.
Other Sensor Philosophies
Various sensors utilizing different technologies have been tried with the purpose of improving grain storage management. One of these is a CO2 sensor. The idea behind this is detection of spoilage in a grain mass so a fan can be activated to correct the problem.
TGM does not utilize such technology, not because it does not work, but because it is too late. It is a reactive approach instead of a proactive approach.
Additionally the implementation is expensive and the life time is unknown.