Main Controls: Output Filters; Main Controls: Demodulator Control - Ametek 7230 Instruction Manual

Auto Offset
This control adjusts the X2 offset and Y2 offset values so that the X2 channel and
Y2 channel outputs are zero. Any small residual values can normally be removed by
calling Auto-Offset for a second time after a suitable delay to allow the outputs to
settle.

5.3.09 Main Controls: Output Filters

The Output Filters controls, shown in figure 5-27, affect both sets of demodulators.
Synchronous
When this box is unchecked, which is the normal mode, time constants are not
related to the reference frequency period. When it is checked and the reference
frequency is 10 Hz or lower, the actual time constant used is chosen to be some
multiple of the reference frequency period, giving a much more stable output at low
frequencies than would otherwise be the case. Note that in this mode, depending on
the reference frequency, output time constants shorter than 100 ms cannot be used.
Fast mode
When this box is unchecked, the instrument's 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.
When it is checked, 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.

5.3.10 Main Controls: Demodulator Control

The Demodulator control, shown in figure 5-28, determines whether the second set
of demodulators is active.
Single
When selected the instrument functions as a conventional dual phase lock-in
amplifier, and only the first set of demodulators is active. It includes both internal
and external reference modes and provides detection either at the reference
frequency or one harmonic of it. Virtual Reference mode can only be used when in
Single Reference mode.
Chapter 5, WEB CONTROL PANEL OPERATION
Figure 5-27, Output 2 Controls
Figure 5-28, Demodulator Control
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