Ametek 7270 Instruction Manual page 58

Chapter 5, FRONT PANEL OPERATION
5-10
The Signal Channel Menu 2 has four controls affecting the instrument's signal input
channel, and a key for accessing Signal Channel Menu 1. Changes to the setting of
these controls can be made by using the adjacent
active selection being shown in highlighted text.
INPUT DEVICE
This control selects the type of input device used for the signal channel connections.
FET (FET input device)
Uses a FET as the input device, for which case the input impedance is 10 M.
This is the usual setting.
BIPOLAR (Bipolar input device)
Uses a bipolar device in the input stage, for the lowest possible voltage input
noise. In this case the input impedance is 10 k. Note that this selection is not
possible when using the AC-coupled input modes.
LINE NOTCH FILTER
This control selects the mode of operation of the line frequency rejection filter and
offers four possible settings out of the seven described in the following table:-
Legend Function
OFF
Line filter inactive
50
Enable 50 Hz notch filter
60
Enable 60 Hz notch filter
100
Enable 100 Hz notch filter
120
Enable 120 Hz notch filter
50/100
Enable 50 and 100 Hz notch filters
60/120
Enable 60 and 120 Hz notch filters
The filter frequencies available (i.e. 50/100 Hz or 60/120 Hz) depend on the setting
of the LINE FREQUENCY control on the Configuration Menu - see section 5.3.15
AUTO AC GAIN
This control selects whether or not the Automatic AC Gain function is active. As
discussed in section 3.3.04, the correct adjustment of the AC Gain in a DSP lock-in
Figure 5-7, Signal Channel Menu 2
keys, with the currently