Chapter 5, FRONT PANEL OPERATION 
5-11 
amplifier is necessary to achieve the best results. This control allows the user to 
select whether this adjustment is carried out automatically or remains under manual 
control. 
  OFF 
 In this setting the AC Gain may be manually adjusted from the Main Display. 
  ON 
 In this setting the AC Gain value is automatically selected by the instrument, 
depending on the full-scale sensitivity. In the mid-range full-scale sensitivity 
ranges the resulting dynamic reserve is between 20 and 26 dB. 
DEMOD2 SOURCE 
When the demodulators are configured for dual reference operation, this control 
selects the signal source for the second set of demodulators 
  SIGADC 
 In this setting the signal input to the second set of demodulators is taken from the 
main signal channel ADC. This is the normal mode of operation. In dual 
reference or dual harmonic mode this means that the two signals being measured 
are applied to the same input connector and share a common path through the 
main ADC. 
  ADC1 
 In this setting the signal input to the second set of demodulators is taken from the 
auxiliary input ADC, ADC1. The full-scale sensitivity is adjustable over the 
normal range of 1 V to 2 nV, but because there is no AC Gain, the effective 
maximum sensitivity is 1 mV. 
  DEMOD1 (Tandem demodulator mode) 
 In this setting the signal input to the second set of demodulators is taken from the 
X-channel output of the first set of demodulators 
Signal Channel Menu 1 
Pressing a key adjacent to the Signal Channel Menu 1 item accesses the Signal 
Channel Menu 1; pressing the Previous Menu key returns control to Main Menu 1. 
5.3.05 Reference Channel Menu 
When Main Menu 1 is displayed, pressing a key adjacent to the Reference Channel 
item accesses the Reference Channel menu, which is shown in figure 5-8.