Chapter 5, FRONT PANEL OPERATION 
5-85 
AUTO 
 This is the same as the ON setting except that if the reference changes the time 
constant will be recalculate to the nearest legal synchronous setting. 
TIME CONSTANT MODE 
This control has two settings, as follows:- 
  NORMAL 
 In this setting, the analog outputs are derived from the output processor. The 
update rate is always 1 kHz, the output filter time constant can be set to values 
between 5 ms and 100 ks in a 1-2-5 sequence, and all four output filter slope 
settings are available. 
  FAST 
 In this setting, the analog outputs are derived directly from the core FPGA 
running the demodulator algorithms. The update rate is increased to 1.0 MHz 
when the time constant is set to any value from 10 µs to 500 ms but remains at 
1 kHz for longer time constants. The output filter slope is restricted to either 6 or 
12 dB/octave. 
Pressing the Output Filter Menu 2 key selects the Output Filter 2 Menu, while 
pressing the Previous Menu key returns control to Main Menu 1. 
5.6.05 Dual Harmonic Output Filters Menu 2 
In dual harmonic mode, pressing the Output Filters Menu 2 key on Output Filters 
Menu 1 accesses the Dual Harmonic Output Filters Menu 2, shown in figure 5-64. 
 
Figure 5-64, Dual Harmonic Output Filters Menu 2 
The Dual Harmonic Output Filters Menu 2 has two controls affecting the 
instrument's output low-pass filters, and a key to access the Output Filters Menu 1. 
Changes to the setting of these controls can be made by using the adjacent   
keys. 
The controls operate as follows:- 
TIME CONSTANT 2 
This control, which duplicates the Main Display control of the same name, is used to 
set the time constant of each of the output filters.