Anfatec AMU5.0-LIA User manual

PCI-BUS LOCKIN AMPLIFIER 1 HZ TO 2 MHZ
Anfatec Instruments AG
Melanchthonstr. 28
08606 Oelsnitz /V.
Germany
Tel.: [phone]
Tel.: [phone]
http://www.anfatec.de
email: [email protected]
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 1 (34)

•Table of Contents
•General Information..........................................................................................................................4
•Specification of the AMU5.0-LIA...............................................................................................4
•Signal Input........................................................................................................................................4
•Reference Output................................................................................................................................4
•PLL.....................................................................................................................................................4
•General...............................................................................................................................................5
•Licence for the software...............................................................................................................5
•Get started.........................................................................................................................................6
•System requirements....................................................................................................................6
•Software installation....................................................................................................................6
•Card and Driver installation.........................................................................................................6
•Check your APIC configuration.........................................................................................................6
•Card Installation.................................................................................................................................6
•Driver Installation..............................................................................................................................7
•Connections to the card................................................................................................................8
•APIC configuration......................................................................................................................8
•LockIn Basics....................................................................................................................................9
•The general idea of LockIn..........................................................................................................9
•Mathematical description...........................................................................................................10
•Noise Measurements..................................................................................................................11
•Example: Electrical Force Microscope......................................................................................12
•Software description.......................................................................................................................14
•Overview....................................................................................................................................14
•Functions in the Menu Line.......................................................................................................14
•File...................................................................................................................................................14
•Option...............................................................................................................................................14
•View.................................................................................................................................................15
•Help..................................................................................................................................................15
•Functions in the function line.....................................................................................................15
•Sweep frequency..............................................................................................................................15
•Sweep bias........................................................................................................................................15
•Oscilloscope...............................................................................................................................15
•Parameter settings......................................................................................................................16
•Time constant...................................................................................................................................16
•RollOff.............................................................................................................................................17
•Dynamic...........................................................................................................................................17
•Coupling...........................................................................................................................................17
•The Meters.......................................................................................................................................17
•Frequency.........................................................................................................................................18
•Amplitude.........................................................................................................................................18
•Phase................................................................................................................................................18
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 2 (34)

•Harmonic..........................................................................................................................................18
•Sweep Frequency.......................................................................................................................18
•Window description.........................................................................................................................18
•Options for the frequency sweep......................................................................................................19
•........................................................................................................................................................21
•How to use two lockin cards in one PC..........................................................................................22
•Installation..................................................................................................................................22
•Simultaneous Usage of two cards..............................................................................................23
•DLL support....................................................................................................................................24
•Working with the DLL in C projects.....................................................................................24
•DLL-Functions...........................................................................................................................25
•Example programs.....................................................................................................................26
•LabView Driver and Support..........................................................................................................27
•Files and Locations...........................................................................................................................27
•Surface and basic description...........................................................................................................27
•Programming directions in LabView.........................................................................................28
•Revision History.............................................................................................................................31
•Manual-related Revisions..........................................................................................................31
•Hardware Revisions...................................................................................................................31
•Software Revisions....................................................................................................................31
•Driver Revisions........................................................................................................................31
Copyright 2002-2019 Anfatec Instruments AG. All rights reserved. Anfatec, and AMU are
trademarks of Anfatec. Other 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
manual.
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.
Important: Please read Anfatec Licence Agreement contained in this handbook before using the
accompanying software programs. Using any part of the software indicates that you accept the terms
of Anfatec Software Licence Agreement.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 3 (34)

ENERAL INFORMATION
SPECIFICATION OF THE AMU5.0-LIA
eneral
Digital Dual-Phase Lock-In Amplifier
Dynamic Reserve > 135 dB
Noise 2.5 nVrms/Hz0.5 @ 100kHz
Time Constants 200 µs ... 5 s
Sensitivity 10 nV ... 10 V
Phase Resolution 0.0001°
SI NAL INPUT
Voltage Input single-ended SMB
Input coupling: dc or ac (f-3dB = 2 Hz)
Input Impedance 1 MΩ || 15 pF
Damage Threshold /- 12 V
Bandwidth dc to 2 MHz
Input Ranges ± 10 Vpp, ± 1 Vpp, ± 100 mVpp
Input Sensitivity 10 nV to 10 V
Input Noise (detected with 10 ms, 12 dB/Oct) Uac = 0 V, 50 Ω, 1 kHz .. 1 MHz
@ 100 kHz, high dynamic reserve < 100 nVrms/Hz0.5 (typ: 35 nV/Hz0.5)
@ 100 kHz, normal dynamic reserve < 5 nVrms/Hz0.5 (typ: 3.6 nV/Hz0.5)
@ 100 kHz, low noise < 4 nVrms/Hz0.5 (typ: 2.5 nV/Hz0.5)
RollOff 6 dB/oct, 12 dB/oct, 24 dB/oct, Sync
Time Constants 200 µs ... 5 s
Amplitude Accuracy < 0.05 % of range
REFERENCE OUTPUT
Internal Oscillator 3 mHz ... 2 MHz
Frequency Resolution 3 mHz
Frequency Accuracy /- 25 ppm from 0 °C to 70 °C
Reference Output Voltage < 1 mVpp ... 15 Vpp
Output Noise
@ 100 kHz, UAC = 0 V < 200 nVrms/Hz0.5
PLL
Frequency range 1 Hz .. 2 MHz
Locking time < (100 ms 10 Cycle)
Phase error < 4 deg @ f = 1 kHz
Input amplitude TTL, sine wave
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 4 (34)

ENERAL
Interface Plug & Play PCIe interface
Drivers Win7 , Win10 (32/64 Bit)
Interrupt rate 40 kHz
Warranty 2 years
LICENCE FOR THE SOFTWARE
The LockIn software is provided with the General Public Licence (GPL). This licence has been
developed within a project of the "Free Software Foundation". It gives the user the liberty, to add
changes in the code and the programmer the security, not to get in trouble due to the users changes.
Most commercial software packages don't use this licence, because they want to keep the right to
sell the newer version later as update. An open software can be changed by the user. So, he can
adapt the software to his problem. Free software, has to stay free, even if the user add some changes.
Therefore, GPL protects the software so, that all programs which are based on a GPL protected
source code has to provided with the same GPL again. The licence also hinders software patenting.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 5 (34)

ET STARTED
SYSTEM REQUIREMENTS
–compatible PC
–free PCI slot
–APIC installed (recommended) - for details see here
–1 MB hard disk space
–Windows 2000 / Windows XP / Windows 7 / Windows 10 // 32/64 Bit
SOFTWARE INSTALLATION
There are two ways for installation:
automatic. Start the setup.exe in the root directory of the installation CD.
Manual: Before installing the driver, install the software. Put the installation disk named “Software
for the AMU5.0” in the disk drive and and copy at least the four needed files
lockin.exe, lockin.ini, lockin.sys and lockin.inf
into a new directory, for instance: C:\Programme\Anfatec\LockIn . On the installation CD, you find
these files under the directories: /bin (*.exe, *.ini) and /driver (*.sys, *.inf).
If you later want to use the source code, you find it in the directory /sources. Please contact us for
newer versions.
CARD AND DRIVER INSTALLATION
CHECK YOUR APIC CONFI URATION
The APIC improves the interrupt control in your system. The APIC will dramatically increase the
performance of the PC. It is installed together with the Power Manager while Windows installation.
Check it as follows:
•Windows 2000
Open “Einstellungen / Systemsteuerung / System / Hardware” (“Configuration / System control /
System / Hardware”) and start the “Geräte Manager” (“Device Manager”). It appears a list of
devices. The information about the APIC is in the submenu “Computer”.
•Windows XP
Open “Systemsteuerung / System / Hardware” (“System control / System / Hardware”) and start the
“Geräte Manager” (“Device Manager”). It appears a list of devices. The information about the APIC
is in the submenu “Computer”.
The APIC is installed, if the “ACPI-Uniprocessor-PC” is shown in “Computer”. If only “Standard
PC” is found there, even the changes of the BIOS will not help, to make Windows use the APIC. If
you find the entry “Standard PC”, you can follow the instructions in the APIC configuration.
CARD INSTALLATION
Switch off the PC.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 6 (34)

Remove the power completely, because PC's keep the supply voltages at the PCI slots on, if the PC
is only shut down.
Plug the card in one of the PCI-slots of your PC and switch on again. Start the setup.exe on the CD.
All related files are copied to the related directories.
DRIVER INSTALLATION
•Windows 2000/ Windows XP
While Windows boots, it finds new hardware. Log in as administrator. WindowsTM will mention,
that it has found new hardware on your computer. If the software is not yet on your computer, you
can copy the recommended files now to your hard disk.
Check the second point, which means “Treiber aus einer Liste auswählen”. Say OK and give the
path to the “lockin.inf” (for instance: C:\Program Files\Anfatec\LockIn\Driver) with the button
“Durchsuchen” (“Search”). Check the driver “LockIn Interface” and finish with “Fertigstellen”
(“Finish””).
•Later re-installation of a driver
Log in as administrator and call in the “System control” the topic "system". Chose the card
“hardware“ and open the “device manager”. It shows all hardware components installed on your PC.
With a double click on the "Anfatec Measurement Unit", the submenu "Anfatec Measurement Unit"
or “Anfatec LockIn” is opened. A second double click opens a window, which shows the properties
of the device.
Select the card “Driver” and start the button “Driver actualisation”. A dialogue is opened, which
asks: “Do you want to actualise the driver?”. In the next window please check the second option
“Search for a suitable driver” and click “OK”. At the question, where the driver is, the right path has
to be given as “other sources”. It is the path, where the new *.inf file is located. Eventually, you
have to select again the right device from a list of possible devices. Check the Anfatec Measurement
Unit again and say “OK” and “Finish”. The PC has to be rebooted in order to activate the new
driver.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 7 (34)
Figure 1: Photograph of the LockIn board and description of the location of the single parts.

•Windows 7/10
Files are located in:
Driver in .\Driver
GUI software in .\App\Win32\LockIn.exe
– start to test the device under 32 bit
in .\App\Win64\LockIn.exe 1
– start to test the device under 64 bit
.\App\Win64\LockIn.exe 2 - if two devices should
work
simultaneously
OTE: In Windows7, the ini-file “user.ini” might be copied automatically in another directory. If you want to
avoid this, make the directory that contains the ini-file writeable by any user.
Source Code of the lockin.exe in .\Manual\App\Delphi7
.\App\DelphiXE7
DLL file in .\DLL\Win32 or .\DLL\Win64
Examples using the DLL in .\DLL\....
Source Code of the DLL in .\DLL\ DLLSourceXE7
Driver Installation:
Connect the USB lockin first. If the system asks for a driver, browse on the USB-Stick for:
.\Driver\version\x86 for 32 bit or
.\Driver\version\x64 for 64 bit operating system.
Select the inf-file.
If the system does not ask automatically, there are two possibilities to solve the problem:
Install through device manager
•Click on Start
•Enter “devmgmt.msc” in the Search Line to open the Device Manager
•Select the “Anfatec Lockin Interface” and right-click to “Update Driver Software”
•“Browse for driver software on your computer”
•provide the path “%YourPath/Driver/version/..”
•select the inf-file
•Say OK when Windows recommends not to install from an unknown driver vendor
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 8 (34)

CONNECTIONS TO THE CARD
Connect the reference output to the excitation
input of your experiment. The signal input has
to be connected to the signal to be analysed.
The microscope control is used for the external
D/A- and A/D-channels, which can be updated
any time.
This card supports digital data outputs, only.
The connector “Controller” provides a digital
reference output signal as 2.8 V LVTTL wit the
same frequency like the sine wave at the “Out”
connector.
APIC CONFI URATION
Attention: this change is critical for your system. It can cause that your computer refuses to
boot. Only administrators should perform this action.
The way to switch on the APIC later, if the system has been installed as “Standard PC” without
Power Management, is described in detail in the computer magazine C't 19/03 on page 190/191 in
German. It works as follows:
Double click on the “Standard PC” icon and say “actualise driver” (Treiber aktualisieren). Check
the second line: “Show all known drivers”. Say OK and check again, that all known hardware
components for this device class are shown (“Alle Hardwarekomponenten dieser Geräteklasse
anzeigen.”. It appears a list on the right sight, which shows “standard PC”, “ACPI-Uniprocessor-
PC” and others. Select now the “ACPI-Uniprocessor-PC” and say OK. Because this change can
cause a real damage on your system, the computer will ask you “Do you really want to exchange
this driver?”. Say “Yes” and complete with “finish”.
When the computer restarts, you have to go into the BIOS setup now! Press “Entf” or “Del”
button on your keyboard during system reboot. In the BIOS, switch on the ACPI mode with “ACPI
Aware O/S = Yes” under the Power Management menu. For most BIOS types, this is only one point
to change. But for some BIOS, the APIC, which is part of the ACPI, has to be switched on
separately. Therefore, check your BIOS settings careful, that the APIC is really switched on.
If the computer does not reboot alone now, you have to reset and to repair your system from the
Windows Installation CD.
Remark: Wrong BIOS settings can cause, that Windows refuses to repair the system from CD. It
will stop with “could not find ntkrnlmp.exe – error code 7” for instance.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 9 (34)
Figure 2: Connections to the LockIn card.
•Figure 3: Pinout of the connector "Controller"
or "Microscope Out".

LOCKIN BASICS
THE ENERAL IDEA OF LOCKIN
A LockIn amplifier is a phase sensitive bandpass filter with a centre frequency f and a bandwidth t.
It has two output signals in parallel: either the amplitude R and the phase j, or the real part X and
the imaginary part Y.
•The centre frequency is the frequency at which the LockIn is searching for its signal.
•The bandwidth gives the frequency range around this centre frequency, from which the output
signal is derived.
•The output signal R is the measured amplitude of the analysed signal at the centre frequency f.
•The phase j is the relative phase shift between the analysed signal and an internal reference signal
with the same frequency.
For analysing the input signal, the LockIn needs an internal frequency reference with a certain
amplitude and phase. (see Fig. 8).
The bandwidth of a LockIn can be visualised by a simple setup. A generator gives a constant
frequency fin signal to the input and sweeping the centre frequency f around the input frequency fin.
Figure 9 shows that the amplitude at the input frequency is always measured with the same value.
For other frequencies, the measured amplitude is dependent on the distance between the actual
centre frequency and the input signal frequency.
A schematic diagram with the basic components of the lock-in amplifier is shown in Figure 2 on
page 9. 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 ωref) 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. Out of them the amplitude R as
well as the relative phase shift φ are calculated.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 10 (34)
Figure 4: Schematic diagram with the basic components of the lock-in amplifier.

MATHEMATICAL DESCRIPTION
A digital LockIn realises its filtering by certain mathematical procedures.
Think, Y(t), the signal to be analised, is dependent on a value X(t). For
instance: we measure a photovoltage U(t) which depends on the light
intensity given by an LED I(t). If the background light intensity is much too
high to detect small intensity changes of the LED light, one can modulate the
light intensity I(t) at a certain frequency ωref and detect with a narrow band
filter at this frequency.
Thus, X(t) is modulated as X(t) = X0X1 cos(wref t). Then, Y(X(t) can be developed into a Taylor-
Series:
Equ.(1)
For the value of Y at the time t, all measurement values Y(t) detected in the period

are used.
This period t should be a whole-numbered multiple of 2pwref. Due to the modulation of X(t) at wref,
modulations of Y(t) at the frequencies m wref with m = 1,2,... are expected. These modulations equal
the Fourier components Y(m wref) with m = 1,2,... of the input signal Y(t), which are given as
Ym=1
∫
−/2
/2
YXte−i m tdt
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 11 (34)
YX0X1cosref t=∑
k=0
∞
YkX0⋅X1
k
k !⋅coskref t⋅YkX= dkY
dX k∣X0k∈
Figure 5: Output signal of a LockIn amplifier for a single frequency input signal of 100
kHz and 20 mVrms amplitude at the input. The time constants have been kept constant.

and together with Equ. 1
Ymref =∑
k=0
∞
YkX0X1
k
k! Km
k
with
Km
k=1
∫
−/2
/2
cosk ref te−i m ref tdt
.
The factors Kmk get zero for k to infinity. For small k, the Kmk remain too big to be neglected. In
order to neglect n-th order parts, the n-th derivative of Y(t) to X(t) has to be negligible.
The first 10 (k = 1 ... 10) coefficients Kmk for the first 4 harmonics m = 1 ... 4 are given in the
following table:
k =
m12345678910
1
1
2
3
8
5
16
35
128
63
256
2
1
4
1
4
15
64
7
32
105
512
3
1
8
5
32
21
128
21
128
4
1
16
3
32
7
64
15
128
NOISE MEASUREMENTS
Lock-in amplifiers are capable to measure noise. They detect a signal at a certain center frequency
ωref with an equivalent noise bandwidth. For a Gaussian noise, the equivalent noise bandwidth of a
real low pass filter is the bandwidth which passes the same amount of noise as a perfect rectangular
filter with the equivalent noise band width.
The equivalent noise bandwidth of the eLockIn is determined by the time constant and the slope of
the used Butterworth filter. It is calculated by
Bn=∫0
∞1
12n d
. (4)
The normalized Butterworth filter noise bandwidths are:
Filter order Bandwidth /
τ
1 1,570796
2 1,110721
4 1,026172
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 12 (34)

In order to measure noise spectra, the resulting data should be divided by the square-root of the used
bandwidth.
The integrated spectrum is taken with a time constant of 10 ms and
a slope of 24 dB (4th order) – bandwidth factor ~ 1 03. The related
bandwidth is then 1/10 ms = 100 Hz. In order to interpret the
result as noise in units of V/Hz0.5 the spectrum should be divided
by 10 Hz0.5(= sqrt(100 Hz)).
EXAMPLE: ELECTRICAL FORCE MICROSCOPE
In this chapter electrical force microscopy (EFM) is briefly presented as an example for the
application of lock-in amplifiers.
EFM is a related technique to the well-established atomic force microscopy (AFM). Its special aim
is to detect electrical forces to learn something about the electrical properties of a surface, for
example about the local distribution of surface potentials on electronic devices or different dopant
concentrations in semiconducting materials.
The fundamental experimental setup shown in Figure 6 is based on a conventional atomic force
microscope: In the non-destructive dynamic non-contact mode, an oscillating metallic tip fixed to a
cantilever is scanning over the surface by means of a piezo scanning device. The distance between
tip and sample can be controlled by monitoring the oscillation amplitude of the cantilever, because
its value is influenced by short-range van der Waals forces. Therefore a reflected laser beam and a
position-sensitive photo-detector are used. A lock-in amplifier analyzes the detector signal at the
cantilever resonance frequency ωr and passes the determined amplitude value to a feedback control
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 13 (34)
Figure 6: Schematic diagram of the EFM experimental setup.

system that re-adjusts the tip-sample distance. The required displacement of the z-piezo can be
recorded as topography signal.
In addition to the topography, EFM detects electrical forces, too. These forces are proportional to
the derivative of the capacitance C of the tip-sample arrangement with respect to the tip-sample
distance z and proportional to the potential difference U squared:
Fel = −1
2
dC
dzU2
. (5)
A possible voltage dependency of C is neglected in this consideration.
The voltage U contains a direct voltage part UDC and an alternating voltage part UAC:
U=UDC UAC⋅cosref t
. (6)
UDC consists of an additional applied bias voltage and, what is especially interesting from the
physical point of view, potential differences caused by different electronic work functions and
charges. For separating the impact of these electrical forces from other forces (e.g. van der Waals
forces), U has to be modulated at the frequency ωref. As a result of this, the measurable photo-
detector signal is modulated, too.
Inserting equation (6) in (5) and using power-reduction formulae of trigonometric functions one can
expect a force between tip and sample at the frequency ωref as well as at 2·ωref. Figure 7 confirms
this prediction: It shows the frequency spectrum of the cantilever oscillation with clear signals at the
mechanical excitation frequency ωr and at the frequencies of the first and second harmonic of the
electrical excitation.
Now two additional lock-in amplifiers (see Figure 6) can be used
to analyze the photo-detector signal at the frequency ωref and 2·ωref
simultaneously. The measured amplitudes of the signals are proportional to the strength of the
electrical forces.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 14 (34)
Figure 7: Frequency spectrum of the oscillating cantilever

SOFTWARE DESCRIPTION
OVERVIEW
Figure 8 shows the main window of the LockIn program, which appears when the program is
opened. For checking the actually detected values, the two meters are used. Basic input parameters
(frequency, amplitude, offset phase and harmonic) can be selected in the right part of the window.
Parameters, which concern the input stage (time constants, RollOff, and input gain) are chosen in
the left part of the window.
The frequency is either the internal frequency (black numbers) or the detected external frequency
from the reference input (grey numbers).
The menu line allows typical Windows functions, while the button in the function line open new
windows with specific functions.
FUNCTIONS IN THE MENU LINE
FILE
Exit - Exit the program
OPTION
•overload
Overload occurs, when the dc input signal exceeds the full scale sensitivity for the selected range.
This full scale sensitivity is 7 Vrms for high reserve, 700 mVrms for normal reserve and 70 mVrms for
low reserve. With this option can be selected whether a beep and/or a color change is shown in case
of overload.
•ext. reference
For LockIn-amplifier versions with PLL (Phase locked loop), the reference frequency can be either
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 15 (34)
Figure 8: Main window of the LockIn program with description of the functions.

the internal oscillator frequency or an external reference frequency. If the “ext. reference” is
selected, the internal PLL is enabled. The locked frequency is shown in grey in the frequency
window. If there is no input signal connected to the reference input, a default frequency of 2 mHz is
shown, but the LockIn is not working properly.
With disabled PLL, the frequency given in the frequency window is written in black.
VIEW
It can be selected, which of the meters is shown.
HELP
About – shows the current program version.
LockIn help – calls the table of contents of the HTML help file supplied with the program
Help as PDF – calls the current manual (AMU24_Manual.pdf) and opens it in the Microsoft
Internet Explorer.
FUNCTIONS IN THE FUNCTION LINE
SWEEP FREQUENCY
Opens the "frequency sweep" window
SWEEP BIAS
Opens the "bias sweep" window
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 16 (34)

OSCILLOSCOPE
The oscilloscope works like a real 3-channel-oscilloscope. Content, scaling type and offset of the
three channels is selectable.
Channel selection: is done from a drop down list, which shows only the available channels.
The two numbers above the drop down list for channel selection display the “scaling factor per
vertical division” (= left number, hint: “y-scale in /div”, example: 12.90 nV/div) and the mean
value. Both are calculated from all data acquired from the left oscilloscope edge till the current
oscilloscope time. Therefore, these numbers are subsequently re-calculated.
Vertical scaling types:
•0..max the scaling is set to maximum value of the channel
•0..fixed the maximum value can be changed by a slider appearing on the right
sight of the scaling type selection
•0..auto the program calculates the optimum, but takes always “0” as minimum
•auto..auto automatically scaled
Time scaling is done with the edit window (right sight) in seconds.
“Save Pic” saves the oscilloscope screen in a bitmap file.
“Draw mode” selects whether the data are drawn as dots or lines.
PARAMETER SETTIN S
TIME CONSTANT
This option selects the used time constant for the low-pass filter. The internal LockIn functions give
the lower limit of 0.2 ms (5 kHz). The possible time constants range in a logarithmic scale between
0.2 ms and 1 s.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 17 (34)

The low-pass filter itself is a Butterworth with an effective noise bandwidth of
Bn=∫0
∞1
12n d
.
The normalized Butterworth filter noise bandwidths are:
Filter order Bandwidth
1 1,570796
2 1,110721
4 1,026172
ROLLOFF
The meaning of the "RollOff" is shown in the curves in Figure 5. It equals the degree of the lowpass
filter. One can chose between 6 dB/oct (1st order), 12 dB/oct (2nd order) and 24 dB/oct (4th order).
DYNAMIC
This switches the input amplification of the LockIn. With "high" dynamic, input amplification is 1.
The maximum signal amplitude is then /-10 V. The "normal" input amplification is 10, which
equals maximum signal amplitudes of /- 1 V. When the low dynamic is chosen, the resolution of
the LockIn is highest, but the signals cannot exceed 100 mV.
COUPLIN
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.
THE METERS
The meters display the LockIn output channels, which are X and Y as well R and Phi, in physical
units.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 18 (34)
Figure 9: Effect of different time constants.

FREQUENCY
If written in black letters, this is the actual reference frequency which is used at the reference output
and as reference frequency for the signal evaluation of the input. Click with the right mouse button
to switch from external to internal reference. In case of internal reference, the numbers are written in
grey.
AMPLITUDE
This is the amplitude of reference output.
PHASE
Allows to give a phase offset between the reference output and the input. In the schematic in Fig. 4,
this phase is equal to the LockIn input parameter “Phase γ”.
HARMONIC
Selects, which harmonic of the reference frequency is evaluated. The possible values range from 1
to 9. When selecting higher harmonics, take care, that, due to lowpass filtering, the maximum input
frequency the LockIn cannot be higher than 2 MHz.
SWEEP FREQUENCY
This window serves the acquisition of frequency dependent spectra of any of the LockIn input
channels. The frequency sweep uses the internal reference. When the PLL is enabled for normal
operation, it will be disabled during frequency sweep.
The number of data points, parameters for the visualisation as well as for the saving and copying the
acquired data can be changed in the option window.
WINDOW DESCRIPTION
“Delay”: is the time delay between each acquired data point. During spectrum acquisition, the
frequency is set to the next value. Then, the system waits “Delay” and takes one single value from
the acquired Channel.
As this delay has to be related to the time constant of the LockIn, the options in the drop down list
for the delay are given in multiples of τ. Thus, independently on the time constant τ given in the
main window, the time constant for the acquisition of the spectrum is always correct.
“from” and “to” define the values of the start frequency and the stop frequency. For the spectrum's
acquisition, one chooses the wanted frequency range, and presses the “start-button”. If the time
constant was very high, the spectrum might take a while. In order to stop the acquisition, the start-
button can be pressed a second time.
“Channel” is a drop down list of available data channels (X, Y, R, and Phi).
“Range back” - click with the right mouse button in the data screen, and a pop-up menu with list
of four frequency ranges appears. The upper one is a standard range, which can be changed in the
“Option/acquire” part. The next three are, from the bottom to the top, the last three used frequency
ranges.
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 19 (34)

OPTIONS FOR THE FREQUENCY SWEEP
The option window provides three cards: “save” - parameters about the saving and copying format
of data, “acquire” – parameters about the data acquisition, and “view” – parameters around the
screen of showing the data.
The saved files and the data copied to the clipboard have an ASCII structure. The data are written in
lines (each frequency value one line) and delimited by the given delimiter (“TAB” in the example)
are saved. The frequency values are only saved, if “Save x-Axis” is checked. All history data are
saved too and also delimited the same character.
Data file example:
1000,00 234,09
1200,00 237,98 ...
Manual Anfatec PCI-Lockin Amplifier AMU5.0 – Rev. 1.01 Page 20 (34)
Figure 10: Window for the spectra acquisition.