IMKO Trime-GW, Operating Instructions Manual

Page: 5 / 35

1.2.3 The analogue output
The measured value is conveyed via the analogue output in the form of electrical current. Two
versions of the instrument are available, 0..20 mA and 4..20 mA. The relationship between the
current,
I , at the analogue output and the grain moisture,

(in %), arises from the following for-
mula:
0..20 mA: Fehler! Textmarke nicht definiert.
  
I 5000
Example: 1 mA = 5%
4..20 mA: Fehler! Textmarke nicht definiert.
   
I 6250 25
Example: 8 mA = 25%
The display units, available as optional extras, present the moisture readings directly as a per-
centage. The analogue port can also be used for connecting a line printer or a controller for regu-
lating the dryer.
1.2.4 Error display and error messages
Errors occurring while measurements are being taken are displayed at the analogue output as
currents greater than 20 mA (see the table below). TRIME-GW, however, is very tolerant of er-
rors. Malfunctions that occur during measurement don not appear at the analogue output until
25% of the readings are show discrepancies. If no more incorrect measurements occur, at least
80% of the values must be free of errors for a valid reading to appear at the analogue output. This
tolerance of errors allows trouble-free operation even when temporary faults occur, which is of
particular significance when used on controllers.
The only "error" that is permitted to appear in operation is error no. 66. It appears when the probe
is not immersed in grain.
The display instruments show occurring faults as "EE.E" or as values above 100% on the display
panel, dependent on the display type. When a line printer is connected, the fault is indicated by a
line at the upper limit or above 100%. To distinguish the type of fault the display instrument or the
line printer must be able to show values above 20 mA.
The following table shows the meanings of the individual faults and the corresponding currents.
Table 1
Fault
no.
Current
0..20 mA
Current
4..20 mA
Displayed
value
Possible cause
30 26.0 mA 24.80 mA 130% Coaxial cable missing or TDR-electronics defect
31 26.2 mA 24.96 mA 131% TDR-measurement incorrect (only in extremely saline
media)
33 26.6 mA 25.28 mA 133%
Salinity too high
34 26.8 mA 25.44 mA 134% Data implausible or EEPROM defective
35 27.0 mA 25.60 mA 135% Power supply too low
62 32.4 mA 29.92 mA 162%
Temperature sensor in the probe: temperature readings
implausible. Sensor faulty or detached from probe; EMC/
process faults; extremely rapid temp. fluctuations
63 32.6 mA 30.08 mA 163%
Temperature sensor in the probe: sensor not recognised
Sensor faulty; wiring broken; short circuit; switch on with-
out probe
64 32.8 mA 30.24 mA 164%
Temperature sensor in the probe: communication prob-
lems
Sensor faulty; loose connection; EMC faults
66 33.2 mA 30.56 mA 166%
Probe not fully immersed in grain
_____________________________________________________________________________
5