IMKO Trime-GW, Руководство по эксплуатации

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1 Instrument description
1.1
The method of measurement
1.1.1 TRIME - The patented TDR method
The TDR method ( T ime- D omain- R eflectometry) is based on a dielectric measurement method in
which the transit times of electromagnetic pulses are determined in order to measure the dielec-
tric constant or the water content.
TRIME systems comprise a probe with parallel metallic rods that are inserted into the flow of grain
and a die-cast aluminium case with an integrated TDR measuring transformer. A high-frequency
TDR- pulse (1 GHz) generated in the instrument propagates along the wave guides inducing an
electromagnetic field around these guides and thus in the material around the probe. Using a
patented method, IMKO has succeeded in measuring the transit time of with a resolution of 10
-12
seconds.
The determined moisture content can either be transmitted via an analogue output (0 or 4...20
mA) to a display in the process control room or fed directly into an automatic process control sys-
tem. In addition, the TRIME systems can be easily networked and extended via a serial bus inter-
face (RS232/V24).
1.1.2 TRIME compared to other methods
In contrast to capacitive, infra-red- or resistance methods of measurement, the TRIME TDR-
technology shows greater indifference to the grain type, the temperature of the product and the
ionic conductivity. The remaining temperature dependency is compensated by means of a grain
temperature measurement in the probe.
The TRIME method fully penetrates a corn volume of 1..2 dm
3
. You thus not only obtain data
about the moisture close to the surface (such as with the infra-red method) but also the water
content of the unground, whole corn. Complex and fault-prone bypass constructions, as required
by the disproportionately expensive microwave method or transmissive infra-red method, can be
dispensed with when using TRIME systems. The modular technology allows later system exten-
sions with minimal expense. TRIME technology is also highly flexible in terms of probe design
thus making it adaptable to numerous applications.
1.2 The operating principle
1.2.1 Measuring with floating mean-value
TRIME-GW constantly takes readings in cycles of 0.5 s and passes them on via the analogue
output. However, not the individual values just recorded are directly output, but the mean value of
a certain number of measurements thereby filtering out any temporary fluctuations that may oc-
cur. These fluctuations can be caused by an uneven distribution of moisture in the flowing grain.
The number of readings from which a final measurement is to be taken, or the averaging time,
can be set depending on the particular application (see page 6).
1.2.2 Temperature compensation
A built-in temperature sensor measures the grain temperature. Thus the measured water content
value is automatically corrected dependent on the grain temperature and the water content. It is
very important that the probe is in the colder exhaust air area of the dryer. It would measure the
air temperature instead of the grain temperature, it was in the heated inlet air zone.
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