Anfatec eLockIn 203 User manual

eLockIn 203
dual input 4-phase DSP lock-in amplifier
models produced after 01/2014
– Manual –
L
L CK CK-I -IN N A AMPLIFIER MPLIFIER 10 10 m mH HZ Z T T 250 250 k kH HZ Z
S
SPECTRUM PECTRUM A ANALYZER NALYZER
D
DATA ATA A ACQUISITI N CQUISITI N
D
DIGITAL IGITAL SCILL SC PE SCILL SC PE
November 2014
Anfatec Instruments AG
Melanchthonstr. 28
08606 elsnitz /V.
Tel.: [phone]
Tel.: [phone]
http://www.anfatec.de
email: mailb[email protected]
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TABLE OF CONTENTS
1 Introduction..................................................................................................................5
1.1 General Functions..................................................................................................5
1.2 Specifications eLockIn203.......................................................................................7
1.2.1 Lock-In Amplifier...........................................................................................................7
1.2.2 scilloscope:................................................................................................................9
1.2.3 AUX In:........................................................................................................................9
1.2.4 AUX ut:......................................................................................................................9
2 Lock-In Basics..............................................................................................................10
2.1 Lock-In Amplification............................................................................................10
2.2 Mathematical Description......................................................................................10
2.3 Characteristical Curves of a Lock-In Amplifier.........................................................12
2.4 Noise Measurements.............................................................................................13
2.5 Example: Electrical Force Microscope.....................................................................14
3 Users manual...............................................................................................................16
3.1 Technical introduction...........................................................................................16
3.1.1 Front Panel.................................................................................................................16
3.1.2 Screen rganization....................................................................................................17
3.1.3 The Menu Tree...........................................................................................................18
3.1.4 Rear Panel..................................................................................................................20
3.2 The LockIn Menu [ LockIn ]..................................................................................20
3.2.1 Input Settings [ LockIn / Input ]..................................................................................20
3.2.2 Reference utput [ LockIn / Ref ]................................................................................23
3.2.3 Display Settings [ LockIn / Display ].............................................................................24
3.2.4 AUX ut [ LockIn / ut ].............................................................................................25
3.3 The Spectra Menu [Spectra]..................................................................................26
3.3.1 Run/Stop [ Spectra / Run ] or [ Spectra / Stop ]...........................................................26
3.3.2 Display [ Spectra / Display ].........................................................................................26
3.3.3 Acquire [ Spectra / Acquire ]........................................................................................27
3.3.4 Save [ Spectra / Save ]................................................................................................28
3.4 scilloscope [ Scope ]...........................................................................................28
3.4.1 Run/Stop [ Scope / Run ] or [ Scope / Stop ]................................................................28
3.4.2 Display [ Scope / Display ]...........................................................................................29
3.4.3 Acquire [ Scope / Acquire]...........................................................................................29
3.4.4 Save [ Scope / Save ]..................................................................................................29
3.5 Measure [ Measure ].............................................................................................29
3.6 Setup [ Setup ]....................................................................................................30
3.7 Handling of parameter settings.............................................................................31
3.8 FTP Data Access...................................................................................................31
3.9 HTTP Web Access.................................................................................................31
3.10 Known Problems.................................................................................................32
4 Remote Control............................................................................................................33
4.1 General Accessing via CGI- Interface.....................................................................33
4.1.1 Technical Requirements...............................................................................................33
4.1.2 Authentication............................................................................................................33
4.1.3 Sending Key Codes to the eLockIn...............................................................................34
4.1.4 Setting Any Values......................................................................................................36
4.1.5 Examples For Keycode peration.................................................................................40
4.1.6 Retrieving Screenshots................................................................................................41
4.1.7 Retrieving Channel Values...........................................................................................41
4.1.8 Get Internal Settings and Status Information................................................................41
4.1.9 Example Program: LockInRemote.................................................................................42
4.2 Use CGI-Functions via Web Browser......................................................................44
4.3 Exported functions of the eLockin.dll......................................................................44
4.4 Remote by Matlab................................................................................................45
4.5 Remote control for the eLockIn in LabView............................................................46
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4.5.1 TCP/IP access by LabView...........................................................................................46
4.5.2 DLL based access by LabView......................................................................................48
5 Software-Update..........................................................................................................50
6 Revision History...........................................................................................................51
6.1 Manual Revisions..................................................................................................51
6.2 Hardware Revisions..............................................................................................51
6.3 Software revision..................................................................................................51
7 Appendices..................................................................................................................52
7.1 Schematic diagram of the signal paths...................................................................52
7.2 Diagram of the lockin amplification paths...............................................................53
7.3 Frontpanel Dimensions.........................................................................................54
7.4 Instrument Specific Test Sheets............................................................................55
7.5 Preamplifier Connector Pinout...............................................................................56
7.6 CE Certificate.......................................................................................................57
7.7 Traceability Chart.................................................................................................58
The manual uses the following style declarations to visualize certain meanings:
This style describes shortly, how to reach a parameter in the
menus. The list of buttons to be pressed is written usually in
these brackets: [ ... ] .
Parameter names changeable in the menus are written in this style.
The parameter values have this style.
In contrast to parameters which are hidden behind some menu entries, the
main menus as LockIn, Measure, ... are directly accessible by buttons, which
are written in this style. Also, file names used for the remote programming
are written in this style.
Examples are written like this.
otes to the user that might be helpful are shown in this style.
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Copyright 2002-2014 Anfatec Instruments AG. All rights reserved. Anfatec, AMU and
eLockIn are trademarks of Anfatec. ther product and brand names may be trademarks
or registered trademarks of their respective owners.
Anfatec Instruments AG assumes no responsibility for any damage or loss resulting from
use of this handbook.
Anfatec Instruments AG assumes no responsibility for any damage or loss resulting from
use of the software. Anfatec Instruments AG assumes no responsibility for any damage
or loss by deletion of data as a result of malfunction, dead battery, or repairs. Be sure to
make backup copies of all important data on other media to protect against data loss.
Using any part of the software indicates that you accept the terms of Anfatec Software
License Agreement.
Manual date: 11/14/14
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1 INTRODUCTION
1.1 GENERAL FUNCTIONS
The eLockIn203 is a versatile scientific instrument that supports the following functions:
LockIn Amplifier
Digital scilloscope
Spectrum Analyzer
Data Acquisition
The instrument works as a stand-alone device with a 5.6 inches TFT display. Its internal
functionality is best described with the following overall schematics:
The two input signals A and B can be used in three different input modes:
Mode A : the input A is given to both AD-converters simultaneously.
Mode A-B : after a first amplification, the difference between A and B is formed
electronically. The resulting signal A-B is given to both AD-converters
simultaneously.
Mode A & B : the two inputs are amplified separately with the same amplification
factor and feed independently into the two AD-converters.
Note: When the H a r m onic is set to 1 and the input c o n f i g uration
A-B or A is chosen, the signals Xn, Yn, Rn and Phin are displayed as
X, Y, R, and Phi and equal the results provided as X1, Y1, R1 and Phi1.
The different stages of input amplification and switching between the three input modes
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Figure 1: Schematic diagram with the basic components of the lock-in amplifier (see page
52).

The signals which have to be analyzed run through analogue amplification stages whose
3 dB bandwidth is 250 kHz. They are converted with a 40 MHz sampling rate. The whole
lock-in analysis is realized in a fully digital design. The digital oscillator output signal is
D/A-converted with a rate of 40 MHz and amplified to provide the reference output for
the user.
All internal signals marked in green (output) or blue (input) color are handled with
approx. 40 kHz rate, so that the shortest time constant available in the system is 25 µs.
Further 96 bit digital low-pass filters extend the time constant range up to 1 ks. The
user has access to all lock-in inputs and lock-in outputs as well as to 8 additional
analogue input channels AUX-In which are converted with 24 bit @ 40 kHz.
ut of this signal variety, the user selects 4 signals in order to display them in acquired
frequency spectra or in the oscilloscope screen.
Besides these general functions, the eLockIn203 provides:
32 Megabytes of internal data storage
USB connection for external flash memory (USB flash drive)
Remote Control via Ethernet access
HTTP-Server
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Figure 2: Schematic of the input stage describing the switching between the three input
modes A, A-B and A &B as well as the position of the input amplification stages in order
to realize the three different input gains.

1.2 SPECIFICATIONS ELOCKIN203
1.2.1 LOCK-IN AMPLIFIER
General
Digital Quad-Phase Lock-In Amplifier
Dynamic Reserve 135 dB
Noise (single ended A) < 5 nVrms/Hz0.5 @ 100kHz
Remote Control Ethernet
Time Constants 0.1 ms ... 1 ks
Full Scale Sensitivity 10 nV ... 10 V in 1-2-5 sequence
Phase Resolution 0.0001°
Signal Input
Voltage Input (A and B) BNC, single-ended (A) or dual
(A&B) or differential (A-B)
Input Coupling DC or AC (f -3dB = 2 Hz)
Damage Threshold +/- 12 V
Full Scale Input Ranges ±3.6 Vrms, ±360 mVrms, ±35 mVrms
Roll- ff 6 dB/oct, 12 dB/oct, 24 dB/oct
Time Constants 0.1 ms to 1 ks in1-2-5 steps or in
Sync-Mode:
1/f to 200/f in 1-2-5 steps
Gain Deviations between Dynamic Ranges: < 1 %
Gain accuracy @ 22°C ±(0.0004 % of range
+ 0.5 % measurement)
Input Impedance ~ 1 MΩ || 10 pF
Bandwidth dc to 250 kHz
Input Noise @ Uout = 0 V, τ = 1 ms with 50 Ω @ input
@ 100 kHz, high dynamic < 300 nVrms/Hz0.5
@ 100 kHz, normal dynamic < 30 nVrms/Hz0.5
@ 100 kHz, low dynamic < 5 nVrms/Hz0.5
Harmonic distorsion - 80 dB
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Current Input (Optional)
Current Input (optional) BNC (for A-input, only)
Input Coupling DC
Damage Threshold 0.12 mA
Full Scale Input Ranges ± 350 nArms, ± 3.5 µArms
Input amplifications 1 MΩ
Bandwidth dc to 1 MHz
Current Input Noise @ Uout = 0 V, τ = 1 ms
@ 100 kHz, < 1 pArms/Hz0.5
Reference Output (for access to the TTL Ref. output see Appendix)
Internal scillator 10 mHz .. > 250 kHz
Internal Frequency Resolution 3 mHz
Frequency Accuracy +/- 50 ppm from 0 °C to 70 °C
Reference utput Voltage < 0.1 mVrms ... 7 Vrms
utput Noise @ Uout = 1 mVrms, τ = 1 ms
@ 100 kHz < 230 nVrms/Hz0.5
Reference Input
Frequency Range 1 Hz .. 250 kHz
PLL Locking Time < (100 ms+ 10 Cycle)
Phase Error < 4 deg @ f = 1 kHz
Input Amplitude TTL or sine signal > 100 mVrms
Input Impedance for TTL 1 MΩ
Input Impedance for sine 1 MΩ (small signals)
1 kΩ (large signals)
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1.2.2 OSCILLOSCOPE:
Available Channels
Lock-in channels of 1st input RA, ϕΑ, XA, YA
external A/D-channels AD1 to AD8
internal data channels f, Uac, In
internal D/A-channels DA5 to DA8
Lock-in channels of 2nd input RB, ϕΒ, XB, YB in “A&B”
Rn, ϕn, Xn, Yn in “A” & “A-B”
Mathematical Channel Noise
Maximum Number of Simultaneously
Displayed Channels 4
Sampling Rate 39.062 kHz
1.2.3 AUX IN:
Number of Available Channels 8
Input Range ± 10 V
Sampling Rate 39.062 kHz
Resolution 24 Bit
1.2. AUX OUT:
Number of Available Channels 8
utput Range ± 10 V
Sampling Rate 156 kHz
Resolution 24 Bit
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2 LOCK-IN BASICS
2.1 LOCK-IN AMPLIFICATION
The lock-in amplifier is a measuring instrument for extracting and amplifying low signals
from noise by means of a correlation analysis. For this method, it is necessary to know
about the time dependence of the signal to be measured. Practically this signal is
modulated at a certain reference frequency ω
ref
and the resulting frequency spectrum is
simultaneously analyzed at ω
ref
. For analyzing the input signal the lock-in amplifier
transforms the time-dependent signal at ω
ref
into the frequency domain and averages it
during the time τ. In other words, the lock-in amplifier can be described as a narrow-
band amplifier with the center frequency ωref and a bandwidth that is determined by the
time constant τ.
A schematic diagram with the basic components of the lock-in amplifier is shown in
Figure 1 on page 5. First of all the received signal is amplified and digitized. Divided into
two separate channels, the signal is multiplied by the mentioned reference signal (with
frequency ω
ref
) and the 90° phase-shifted reference signal respectively. The reference
signal is generated with the lock-in's digital oscillator. An additional implemented phase
displacement Ψ enables to compensate phase differences
caused by the measuring equipment. After multiplication, the
resulting signals are low-pass filtered and provide now
information about the real part X and the imaginary part Y of
the analyzed signal relating to the phase position of the
reference signal. ut of them the amplitude R as well as the
relative phase shift φ are calculated.
2.2 MATHEMATICAL DESCRIPTION
In this chapter, a short mathematical description of the multiplication and integration
steps as the key procedures of a digital lock-in amplifier is given.
For instance, one tries to analyze the noisy signal s ( t ) that depends on a value v ( t ). v ( t )
itself may consist of a constant part v0 and an additional periodic time-dependent part
with the amplitude v1 and the frequency ωref :
vt = v0v1cosref t
. The latter
term modulates the analyzed signal amplitude
svt
.
Then,
svt
can be developed into a Taylor series:
sv0v1cosref t = ∑
k=0
∞
skv0⋅v1
k
k!⋅coskref t
(1a)
with the derivatives
skv0 = dks
dvk
v=v0
k∈ ℕ
. (1b)
Inside the lock-in amplifier
svt
is multiplied by the reference signal with frequency
ωref and integrated over the time τ. That means, in order to determine the value of s(t)
at the time t, all measured values in the past time interval τ have to be taken into
account. Therefore τ should be a multiple of 2π/ ω
ref or bigger because it should contain
at least one period of oscillation to receive correct results.
Beside the modulation at ωref, modulations of s(t) at the frequencies m·ωref with m = 1, 2,
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
R
X
Y