Antec Scientific DECADE II 171, User Manual, Page: 81 / 87

CHAPTER 13 Dummy cell 81
C H A P T E R 1 3
Dummy cell
External dummy cell
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 trouble shooting
procedure.
The dummy consists of a resistor (R) of 300 M

and a capacitor (C) of 0.47

F in parallel. The current is measured over the resistor according 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 functions as a ‘noise
generator’ and in fact resembles the capacitance of a well-functioning VT-03
flow cell in an ideal HPLC set-up.
The noise generated via the dummy should be less than 2 pA if the filter of
the controller is set to off, provided that the dummy is within the fully closed
Faraday shield at the same position as the flow cell (see Table XII for
settings). With a 1 second risetime the noise should be better than 1 pA.
Table XII. Dummy cell test settings.
Parameter Setting
Cell potential 800 mV
Cell current
2.67+/- 0.05 nA (read-out)
Oven 30 °C, stable
Filter off (or as specified)
Range 100 pA/V
The results of the dummy test must be comparable with the test sheet
supplied with your controller. If not, please consult your supplier.