ELTRA CS-800, Руководство пользователя

Страница: 85 / 158

85
TP 24: Output section [3]
TP 23: Output section [4]
TP 20: Analog GND
NOTICE
Use a very thin screwdriver. With a big screwdriver, the trimmer can be
mechanically destroyed before you feel it. The screwdriver should never get in
touch with the hole resp. the housing of the preamp, otherwise the trimmer may be
mechanically stressed and break.
4.2.6
109B
Voltage of a base line is too high (higher than 9.5V)
The optimal value for the base lines of the IR-paths is about 8V. Golden paths
have the effect to become more reflective in the first few months of their operation.
To compensate this effect, the original value of the golden paths base line should
be adjusted at 5 V. In case of a long golden paths (300mm) having sensors
including on-chip preamplifier, the cell output sometimes cannot be adjusted down
to the required 5 to 6V by turning counter clockwise the trimmer in the preamplifier.
(Outputs: TP22 to TP25 against AGND = TP20).
In this case the IR sources voltage has to be reduced until you get a base line of
the troubled golden cell down to about 5 to 6V. You will then need to increase the
gain of the other cells preamps to get their base lines back to the range of 8V.
4.2.6.1 Source voltage – reducing
1. Take the IR cell out of the analyser.
2. Power the cell by an external 24VDC power supply connected to J1 of the
IRC board.
3. If the external power supply cannot supply 5A then set a jumper on position
2 (Test °C) of JP1 in order to switch off the temperature control so that a
power supply of 1A is adequate. If a jumper is available on position 3 or 4
(Analysis), this jumper can be moved to position 2. The positions 3 and 4 are
simply parking positions for jumpers to simply be available when needed.
There are no tracks connected on the pins of the (Analysis) positions 3 and 4
of JP1.
4. Make sure that the gain of the preamplifier in question is adjusted to a
minimum gain. To do this, turn its trimmer counter clockwise up to the end of
trimmer range. These trimmers have a maximum of 20 turns. When the end
of range has been reached, you can hear a gently silent click with each turn.
It is not possible to feel any mechanical resistance on the screw driver.
5. Measure the actual source voltage between on TP7 against GND=TP1 and
note the value.
6. Turn the potentiometer R80 of the IRC board counter clockwise up to the
end of its range. (Maximum gear range = 20 turns).
7. Switch off resp. disconnect the power supply.
8. Move the jumper of JP2 to position 5.
9. Connect the 24V power again.
10. Connect the multimeter to the cell output which has to be adjusted.
11. Wait for the sources to warm up until the output voltage will almost reach its
maximum value.
12. Turn the trimmer R80 slowly clockwise until the base line of the cell in
question has reached 8V. In case of a clean golden path, adjust between 5V
and 6V instead of 8V.
13. Adjust the outputs of other cells (not golden paths) to have between 7 to 8V
by adjusting the gains of their preamplifiers.
14. Set the jumper of the JP1 from position 2 (Test °C) to Position 3 (Analysis).