Ametek 7270 Instruction Manual page 154

Dsp lock-in amplifier
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Chapter 6, COMPUTER OPERATION
TC [n]
TC.
SYNC [n]
SLOPE [n]
6-16
Filter time constant control
The value of n sets the output filter time constant in accordance with the following
table:
NOISEMODE
= 0
n
time constant
0
10 µs
1
20 µs
2
50 µs
3
100 µs
4
200 µs
5
500 µs
6
1 ms
7
2 ms
8
5 ms
9
10 ms
10
20 ms
11
50 ms
12
100 ms
13
200 ms
14
500 ms
15
1 s
N/A means that n is an illegal value under these conditions.
The TC. command is only used for reading the time constant, and reports the current
setting in seconds. Hence if a TC 12 command were sent and the noise measurement
mode was turned off, TC would report 12 and TC. would report 1.0E-01, i.e. 0.1 s or
100 ms.
Synchronous time constant control
n
Effect
0
Synchronous time constant disabled
1
Synchronous time constant enabled. The actual time constant is recalculated
when the TC setting is changed, but not if the reference frequency changes.
2
Auto synchronous time constant enabled. The actual time constant is
recalculated when the TC setting is changed and also if the reference frequency
changes.
Output low-pass filter slope (roll-off) control
When the fast analog output mode and noise measurement mode are turned off
(FASTMODE 0 and NOISEMODE 0), the selection is according to the following
table:
n
Slope
0
6 dB/octave
1
12 dB/octave
2
18 dB/octave
3
24 dB/octave
NOISEMODE
= 1
time constant
n
N/A
16
N/A
17
N/A
18
N/A
19
N/A
20
500 µs
21
1 ms
22
2 ms
23
5 ms
24
10 ms
25
N/A
26
N/A
27
N/A
28
N/A
29
N/A
30
N/A
NOISEMODE
NOISEMODE =
= 0
1
time constant
time constant
2 s
N/A
5 s
N/A
10 s
N/A
20 s
N/A
50 s
N/A
100 s
N/A
200 s
N/A
500 s
N/A
1 ks
N/A
2 ks
N/A
5 ks
N/A
10 ks
N/A
20 ks
N/A
50 ks
N/A
100 ks
N/A

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