Antec Scientific ROXY Exceed, Руководство пользователя, Страница: 116 / 126

116 211_0010 - ROXY Exceed user manual - rev 04
Remedy: In the event it does happen, the issue can be simply solved by
setting the Compensation to OFF (Comp = OFF) in the STAT screen or
CDS control software. Subsequently, wait till the background current is sta-
ble/stabilized and execute an Autozero again.
In the case event tables are programmed in LC methods in the CDS soft-
ware with an Autozero action, make sure that the autozero is programmed
in a part of the chromatogram were the signal is stable. So at the begin-
ning of the run, during the hold-up time (so before the unretained/solvent
peak elutes). Or at the end of the run.
Dummy cell test
External dummy cell
An external dummy flow cell (pn 250.0040) is shipped with every ROXY
Exceed instrument for troubleshooting purposes and maintenance checks.
The dummy cell test can be performed standalone via the LCD display in
combination with an A/D converter (ROXY Exceed only) or via the Dia-
logue Exceed / DataApex Clarity software. A successful dummy cell test
confirms that the controller, including the cell cable, functions properly. If
the result of the noise measurement with the dummy cell is within specs,
the controller is excluded in a troubleshooting procedure.
Fig. 60. Left: schematics of external dummy flow cell.
Right: photo of the external dummy flow cell (pn 250.0040).
The dummy flow cell consists of a resistor (R) of 300 MOhm and a capaci-
tor (C) of 0.47 µF in parallel. The current is measured over the resistor ac-
cording to Ohm’s law (V = I x R), hence with a working potential of 800 mV
the current drawn will be about 2.67 nA. Slight differences as to this (ideal)
value are due to the tolerance of the resistor (± 1%). The capacitor func-
tions as a ‘noise generator’ and in fact resembles the capacitance of a