Ametek 7280 Instruction Manual page 120

Chapter 5, FRONT PANEL OPERATION
5-74
PHA or θ deg
+180
+90
-0
+0
-90
-180
FAST
In dual reference or dual harmonic mode when the analog outputs operating mode is
set to Fast, the CH1 and CH2 analog outputs are derived either from the first stage of
output filtering or from the output processor. The selection of which connection is
made, and the resulting output update rate, depends on the setting of the two output
time constant controls, as shown in table 5-3 below.
Time Constant 1 Time Constant 2
(Harmonic 1 or
Internal
Reference)
≤ 4 ms
≤ 4 ms
≥ 10 ms
≥ 10 ms
Table 5-3, Analog Output Update Rate - Fast Mode - vs. TC1/TC2
Note that although the maximum effective time constant of the analog outputs is
limited in the first three cases to 4 ms, the time constant applying to the digital
outputs (i.e. front panel displays and values returned over the computer interfaces) is
always the set value. For example, if TC1 were set to 500 µs and TC2 to 100 ms with
Fast mode selected then the time constant applying to the digital outputs of Harmonic
2 or the External Reference (i.e. TC2) would be 100 ms.
In the Fast mode with dual reference or dual harmonic mode the output filter slope is
fixed at 6 dB/octave and there is no choice as to the setting for the
CH1 ANALOG OUTPUT and CH2 ANALOG OUTPUT controls, which are fixed as follows:-
CH1 ANALOG OUTPUT
X1% (2.5V fs)
The CH1 connector on the rear panel will output a voltage related to the X1%fs
front panel display as follows:-
X1%
+300
+100
0
-100
-300
CH1/2 Voltage
0.0 V
-4.5 V
-9.0 V
9.0 V
4.5 V
0.0 V
CH1/CH2 Analog
(Harmonic 2 or Output Update
External
Reference)
≤ 4 ms
≥ 10 ms
≤ 4 ms
≥ 10 ms
CH1/2 Voltage
7.5 V
2.5 V
0.0 V
-2.5 V
-7.5 V
Effective maximum TC
at CH1 or CH2 Analog
Rate Outputs
7.5 MHz
7.5 MHz
7.5 MHz
1 kHz
4 ms
4 ms
4 ms
100 ks