Chapter 5, WEB CONTROL PANEL OPERATION 
5-26 
Dual 
When selected both sets of demodulators are active, and can be used in the following 
ways: 
  Dual Reference 
In dual reference mode the model 7230 can make simultaneous measurements at 
two different reference frequencies. These can be internal or external, subject to 
the limitation that if two external references are used, one of them cannot be 
greater than 3.0 kHz. The Reference controls under Reference 1 and Reference 2 
are used to select the source of reference for each demodulator, and for this 
mode will be set to different sources. 
  Dual Channel Detection 
Normally the signal input in dual reference mode is common to both 
demodulators, and uses the main signal channel. However, it is possible to use 
the auxiliary ADC 1 input as the signal input to the second set of demodulators, 
allowing the instrument to function as two independent lock-in amplifiers, Note, 
however, that in this mode there is no adjustable AC Gain in the ADC 1 input 
channel so the range of full-scale sensitivity settings for the second set of 
demodulators is limited. 
   Dual Harmonic 
Dual harmonic mode allows the simultaneous measurement of two different 
harmonics of the input signal. The Reference controls under Reference 1 and 
Reference 2 are used to select the source of reference for each demodulator, and 
for this mode will be set to the same source, with each Harmonic control set to a 
different value. 
  Tandem Demodulation 
This is essentially the same as dual reference mode but with the input to the 
second set of demodulators taken not from the main signal channel or ADC 1 
input but from the X-channel output from the first set of demodulators. It allows 
the instrument to detect the amplitude of a low frequency modulation of a 
higher-frequency carrier signal. 
5.3.11 Main Controls: Status Indicators 
 
Figure 5-29, Status Indicators 
The Status section gives a quick overview of the instrument status. 
Input limit 
This is the zero to peak value above which the instrument will be in input overload, 
based on the present AC gain setting. 
Dynamic reserve 
This is the calculated level of Dynamic Reserve based on the present sensitivity and 
AC gain settings. 
Status byte and Overload byte 
These two arrays of LED’s show the bit values in these two bytes, which are defined