Anfatec eLockIn 203, Manual

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Note: If the Beep function
[ Setup / Beep ]
is enabled, the instrument
beeps every time it detects an input overflow.
Input Coupling
[ LockIn / Input / Couple ]
If the specification of the instrument allows it, this option switches between DC coupled
input and AC coupled input.
Note: The 3dB corner frequency of the input high pass is around 2Hz.
Reference frequencies around 2 Hz and below may cause misleading results.
Time Constant [ LockIn / Input / Time ]
This parameter is related to the low pass filters in the lock-in amplifier. It describes the
3dB-cut-off frequency f
c
of the filter as:
τ
=
1
f
c
.
τ
might be defined as time period without synchronization to the period
length related to the currently used as reference frequency. Then, the
eLockIn
integrates over the time τ . Those filters refer to the entries in
[Tau]
and
[Tau1]
.
Starting from software version 1.15 and currently for the eLockIn205,
only, the entry in
[Sync]
acts in series with the Butterworth low pass
filter. This Sync-Filter integrates over an integer number of periods
synchronized to the current period length. This allows a time-optimized
data acquisition at low frequencies.
The sync-filter produces an output, which contains steps (Example: at 1
kHz frequency with Sync=1, one gets a new output value exactly after 1
ms. Thus, the analogue output, which is sampled with 1 MHz, provides
1000 constant values before it jumps to the next value.). The Butterworth
filter smooths these edges.
Enable Sync-mode: go to the
Sync
entry (2 nd from the top) and turn the knob right
or use
up
. The entry
Off
turns into a number (could be
1,2, ... ,200
), which is the
amount of periods to be used for integration.
Disable Sync-Mode: go to the
Sync
entry and turn the knob left or use down , until
the
number
turns into
Off
.
The time constants below the entries
Tau
and
Tau1
always stay active.
Please note the following:
•
When the external reference is used, the Sync-filter might increase the
measured signal noise.
•
When the time constant is larger than Sync/f, then the Sync-filter has not much
effect.
In time based mode,
Tau
equals the integration for channel A (
Input/Config
=
A&B ) or the n-th harmonic (
Input/Config
= A or A-B ), while
Tau1
equals the
integration for channel B (
Input/Config
= A&B ) or the 1 st harmonic
(
Input/Config
= A or A-B ). The two entries can be changed independently on each
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