Signal Output
Zeroing signal output
71
Figure 5-3
1.0 mV maximum output level
+ 1.000 mV
+ 0.100 mV
+ 0.006 mV
0mV
Constant 0.1 mV
detector background
HP 5890 SERIES II electrical zero
signal
0.9 mV usable
dynamic range
dynamic range
1.0 mV usable
O
U
T
P
U
V
O
L
T
A
G
E
T
1 mV Output: Canceling Baseline Offset (the self- function)
pressed
ENTERZERO
ZERO
Effect of on the +1 mV Analog Output
ZERO
The example in Figure 5•2is in terms of the +1 V analog output. In
Figure 5•3,identical treatment is made for the +1 mV output, except that
the signal is shifted to an offset somewhat above electrical zero. This
ensures a small positive offset (about 6% of full scale) in pen position at a
connected chart recorder, and permits uninterrupted plotting, even if a
small negative baseline drift occurs.
Once current
ZERO
setpoint value is displayed for the desired signal
channel, pressing
ENTER
causes the value to be changed to the current
signal value.
Self•
ZERO
should be done only at times of quiet chromatographic
activity (i.e., not during a run). To do so during an active run may cause a
baseline shift at the recording/integrating device.
