Foss Infratec 1241, Service Manual

Page: 27 / 212

Infratec™ 1241 Grain Analyzer
Service Manual 1001 5015 / Rev. 4 2:17
The TWU is designed to receive sample from the Infratec in small sub-samples into
a measurement cuvette. The surface of the measurement cuvette is then skimmed flat
with a wiper arm and the measurement taken.
The TWU then discharges the sample into the sample drawer. The commands to
operate the TWU originate from the DSP board. All commands come over the I2C
serial bus. The I2C is a 2-wire serial bus consisting of data and clock. There are two
buses of this type on the TWU PCB, one to the DSP and the other to the EEPROM.
The EEPROM fitted on the TWM PCB is provided to hold the mass calibration
constants. The control of the wiper arm is done with a step motor with an encoder.
At start-up the wiper arm moves between the physical end positions. Then a couple
of pulses are taken away in each end. The calculated positions are HOME and FAR
positions.
Below is a description of the weighing process for Infratec 1241 Test Weight
Module:
1. Activate the Test Weight Unit.
Check in the User menu under Application models/Test Weight/Setup/General
settings, that "Enabled" is set to ON.
2. Choose an Application model that include test weighing. It's important that the
twm.ini file is included. It is also possible to create a new Application model. Go
into the User menu and choose Application models/Test Weight/Setup/Test
Weight Models.
3. Pour the sample into the hopper.
4. Press the analyse button (or use F´9 on the external keyboard)
The empty weight of the test cell is first measured. Then the conveyor in the
Infratec Measuring Unit deposits sub-samples in the sample cell, where NIT
analysis takes place. After analysis of each sub-sample, the bottom shutter of the
sample cell opens, depositing the grain in the cuvette of the Test Weight Unit. A
level sensor detects when the TWU cuvette has been filled and analysis of the
remaining NIT sub-samples are temporarily halted.
A wiper arm levels off the test cell to ensure proper cell packing and consistent
sample volume. The weight of the grain in the test cell is then determined as the
difference between the full measurement and the empty measurement after
which the Infratec makes all necessary calculations and adjustments. The shutter
at the bottom of the test cell is then opened, allowing the grain to fall into the
sample collection drawer, and the analysis of the remaining NIT subsamples is
resumed. The grain from these sub-samples simply passes directly through the
TWU cuvette).
5. The NIT results, along with test weight, are then presented on the LCD display
of the Infratec.