32 DECADE user manual, edition 9
There is much overlap in the recorder range settings offering flexibility as to
maximum zero compensation (Table IV). For example, if a chromatogram is
acquired at 10 nA, the nA or µA range can be selected (Table IV). With a high
background current the µA is chosen (max. 16 µA compensation), at a low
background the nA range is preferred (max. 160 nA compensation).
The resolution of the zero compensation is 16 bits per selected integrator
range. At a high maximum compensation, the compensation circuit uses
larger steps to reach a 0 V output, hence the resolution of the zero
compensation decreases. Therefore, a compromise is made between
maximum zero compensation and resolution. To maintain a high auto zero
resolution with accurate zero settings, the maximum compensation is
decreased with the integrator range.
Table IV. Recorder ranges and maximum zero compensation.
Range
pA
nA µA
10
20
50
100
0.1
200
0.2
500
0.5
range
1000
1.0
overlap
2000
2.0
5000
5.0
10.0
0.01
20.0
0.02
50.0
0.05
0.10
0.20
0.50
1.00
2.00
5.00
maximum zero compensation (nA)
16
160
16000
In certain cases, when a small peak is ‘blown up’ with integration software, a
typical stepwise (0.5 mV = 1 bit) peak profile is seen (Fig. 7). In that case the
recorder output resolution is not sufficient, and the detector should be set at a
more sensitive recorder range.
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