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5.3 R

ESONANCE

D

ETECTION

It is very typical to employ lockin amplifiers to detect resonances of external systems. The
reference output of the lockin amplifier excites the system, while the frequency dependence of its
reaction is analysed plotting R and Phi vs. f.

The application lockin.exe allows to sweep the frequency. The result is shown in these figures:

The circuit answers with 115 mV signal on 1 V excitation. The Q of this analogue circuit is quite
low (only 9), so that the width of the detected resonance peak, whose centre frequency is found
at 50 kHz, almost reaches 5 kHz.

Manual Anfatec PCI-Lockin Amplifier AMU2.4 – Rev. 1.10 dated 30/09/20

Page 25 (70)

Figure 18: Circuit diagram qucs/resonanzkreis.sch a photograph of the

resonance circuit connected to the USBLockIn250.

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Содержание AMU2.4

Страница 1: ...MHz Anfatec Instruments AG Melanchthonstr 28 08606 Oelsnitz V Germany Tel 49 0 37421 24212 Fax 49 0 37421 24221 http www anfatec de email mailbox anfatec de Manual Anfatec PCI Lockin Amplifier AMU2 4...

Страница 2: ...iguration 10 3 LockIn Amplification Basics 11 3 1 The general idea of Lockin Amplification LockIn 11 3 2 Mathematical description 12 3 3 Time constant Definition 13 3 4 RollOff Definition 13 3 5 Noise...

Страница 3: ...Working with the DLL in C projects 33 6 2 DLL Functions 34 6 3 Example programs 37 7 Remote Control with LabView 38 7 1 Files and Locations 38 7 2 General Programming Directions in LabView 39 7 3 Desc...

Страница 4: ...Revisions 64 11 1 1 Till 19th June 2007 64 11 1 2 10th April 2008 64 11 1 3 10th Frebruary 2009 64 11 2 Hardware Revisions 64 11 2 1 1st November 2006 Rev 2 2 to Rev 2 3 64 11 2 2 1st December 2006 Re...

Страница 5: ...age 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...

Страница 6: ...ypical Input Noise Uac 0 V 50 W input 100 kHz high dynamic 300 nVrms Hz0 5 100 kHz normal dynamic 50 nVrms Hz0 5 100 kHz low dynamic 8 nVrms Hz0 5 RollOff 6 dB oct 12 dB oct 24 dB oct Time Constants 0...

Страница 7: ...ammer 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...

Страница 8: ...t 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...

Страница 9: ...d 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 s...

Страница 10: ...ekomponenten dieser Ger teklasse 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 chang...

Страница 11: ...s 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...

Страница 12: ...tiple of 2p w ref Due to the modulation of X t at w ref modulations of Y t at the frequencies m w ref with m 1 2 are expected These modulations equal the Fourier components Y m w ref with m 1 2 of the...

Страница 13: ...the lockin amplifier will be detected with 0 707 times it amplitude 3 4 ROLLOFF DEFINITION The slope of the signal decay in Fig 5 is defined by the Roll Off without affecting the detection bandwidth...

Страница 14: ...ndwidth Butterworth Filter ENBWBW 1 sqrt ENBWBW 1 6 dB oct 1 570796 0 79607 2 12 dB oct 1 110721 0 948849 4 24 dB oct 1 026172 0 987165 In order to scale noise spectra the resulting data should be div...

Страница 15: ...erence input grey numbers The menu line allows typical Windows functions while the button in the function line opens new windows with specific functions This software can be started as often as many U...

Страница 16: ...the LockIn is not working properly With disabled PLL the frequency given in the frequency window is written in black 4 2 3 VIEW It can be selected which of the meters is shown Devices Select whether t...

Страница 17: ...x 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 t...

Страница 18: ...nput 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 th...

Страница 19: ...he saving and copying the acquired data can be changed in the option window 4 5 1 WINDOW DESCRIPTION Delay is the time delay between each acquired data point During spectrum acquisition the frequency...

Страница 20: ...a 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...

Страница 21: ...hboured values while the data are taken This makes sure that even small peaks can be found in an overview spectrum with only some 100 data points Standard frequency is the range which appears at the t...

Страница 22: ...st but one curves are displayed The actual curve is always of black colour The last is red and the last but one is green More curves get the usual next colours from the WindowsTM palette If Draw vecto...

Страница 23: ...ra are saved or copied to clipboard in order to be visualized in another program Teh result is shown in Fig 12 A more detailed explanation how this time constant is related to the detection bandwidth...

Страница 24: ...observes that all three curves meet in two points that represent the 0 7 times the amplitude of the signal This shows that the detection bandwidth is kept independent on the RollOff At the same time t...

Страница 25: ...e allows to sweep the frequency The result is shown in these figures The circuit answers with 115 mV signal on 1 V excitation The Q of this analogue circuit is quite low only 9 so that the width of th...

Страница 26: ...ure of qucs The result of the ac simulation is then plotted in a diagram and shows the noise voltage extension nv to be higher around the resonance of this circuit According to this the peak noise of...

Страница 27: ...possible effect on the result A single frequency sweep over an appropriate range results in the following spectrum The software offers averaging of subsequently taken spectra With this nice feature t...

Страница 28: ...tage noise and the input current noise All these components are independent on each other so that they do not add up linearly U1 U2 UN but orthogonally CALCULATION OF THE NOISE VOLTAGE Voltage Noise R...

Страница 29: ...s original Fourier components which are all odd higher harmonics of the base frequency of the square wave form The amplitudes of the single Fourier components are the peak amplitudes detected all odd...

Страница 30: ...according to the following formula The result of the following measurement was taken from a tube with a length L 0 257 m and a diameter of d 0 043 m Using the sound speed in air v 343 m s the first 8...

Страница 31: ...ts the amplitude of sound Now the frequency of the loud speaker was swept while keeping its amplitude constant As a result the transfer function of this tube showing the acoustical signal to be amplif...

Страница 32: ...s In addition to this the effect of an dc offset on the input signal can be discussed at this example The microphone delivers a signal with a certain DC offset With short time constants this signal at...

Страница 33: ...5 0 by opening Project Add to Project see figure Chose the lockin lib as the file to be added If the lockin lib does not exist it can be created from the command line open the command prompt by runni...

Страница 34: ...ON SetLockInTimeBase gives back the IdleCount which is calculated from the given TimeBase and PointsPerDivision If the setting of the current device succeeded is given back by SetUsedDevice and GetVe...

Страница 35: ...ot overwrite the PLL setting anymore SetLockInTimeConst function SetLockInTimeConst TimeConst integer integer sets the time constant for the low pass filter TimeConst 0 10 s 1 20 s 2 50 s 0 1 ms 4 0 2...

Страница 36: ...ponding X Y and R Data The length of all four arrays must be 1024 0 1023 LabView should reserve the memory and provide the pointer to these arrays for the DLL The parameter lLength is to the number of...

Страница 37: ...tion so that this multiple lockins can be addressed independently see also page 48 GetVersion function GetVersion PChar Returns the hardware serial number e g 280007 the version number of the driver e...

Страница 38: ...ut and internal parameters of the USB LockIn250 Named_Input_Lockin vi sets the input and internal parameters of the lockin specified by a device string only useful if more than one USB LockIn250 is us...

Страница 39: ...al type signed 32 Bit Integer longint numerical type signed 32 Bit Integer PInteger numerical type signed 32 Bit Integer Pointer to value PDArray array type 8 Byte Double 1 dimension array pointer lon...

Страница 40: ...ric type Double They are used unit less in this file but their units are meant in Hz Volts and Degree respectively Beside the frequency input the current frequency is displayed Also an additional swit...

Страница 41: ...lope harmonic and amplitude For change these the sub vi Input_Lockin vi is called When the VI file runs one spectrum is acquired During the spectra acquisition the current frequency is monitored To ge...

Страница 42: ...5 the input of the lockin amplifier is supplied with a 10 kHz square wave containing all odd higher harmonics of 10 kHz while the internal reference of the lockin is swept from 1 kHz to 100 kHz The re...

Страница 43: ...uses the SubVI GetUnitAndRangeFromString vi to get MaxRange in Volts from the string provided by the Display Range Combobox e g 0 01 from 10 mV With an Output Amplitude of 10 mV the AUX0 output at a...

Страница 44: ...rrent AUX displayed in Volts Example Diode see Diode AUX Manual Anfatec PCI Lockin Amplifier AMU2 4 Rev 1 10 dated 30 09 20 Page 44 70 Figure 37 Frontpanel of the AUXRamp_Lockin vi The Aux output is c...

Страница 45: ...pendence whether a USB LockIn250 or a PCI LockIn is connected to the PC If the chosen output channel is Phi the Display Range Combobox is not shown its display range always is set to 180 For the other...

Страница 46: ...nge of the supplied String The VI Nase_LockIn vi in LabView9 folder only demonstrates how a PLL can be realized with the USBLockIn and Labview It consists of two parts Part 1 starts with an initializa...

Страница 47: ...also be set as the reference phase These two values will be shown as f0 and PhaseX accordingly Now the two diagrams become invisible and a new graph appears The new diagram shows the new phase multip...

Страница 48: ...dll open the program Lockin exe enable View Devices if not already shown right click on the device string that corresponds to the chosen USBLockIn250 and copy it paste the copied string into the input...

Страница 49: ...t their arguments as ctypes integer ctypes c_int32 double ctypes c_double String ctypes c_wchar_p 8 3 MULTIPLE DEVICES IN PYTHON To work with more than one Lockin Device at one PC one has to follow th...

Страница 50: ...1 Lockin dll Device2 MyClass MyDevice ID2 Lockin2 dll If only one device is connected to the PC the ID of this device is not required to be known One can call this single device by Device1 MyClass MyD...

Страница 51: ...ansform time dependent signals into the frequency space and thus detect periodicities in these signals This method is also known as Fourier analysis or spectrum analyzer function One easy to understan...

Страница 52: ...tude is shown in a double logarothmic plot Bode Plot Thus the application Network_analyzer py generates two graphs one for the Amplitude and the second for the phase displaying them in one plot with t...

Страница 53: ...n measurement 1 588 Hz 498 Hz 2 1177 Hz 1058 Hz 3 1765 Hz 1645 Hz 4 2353 Hz 2264 Hz 5 2942 Hz 2900 Hz 6 3530 Hz 3536 Hz 7 4118 Hz 4155 Hz 8 4707 Hz 4774 Hz For the experimental realization a loud spea...

Страница 54: ...effect of an dc offset on the input signal can be discussed at this example The microphone delivers a signal with a certain DC offset With short time constants this signal at f 0 Hz is not supressed e...

Страница 55: ...ailable input signals is displayed In 0 X 10 Y 11 R 12 Phi 13 Finally it displays two graphs In over AUX and AC R over AUX EXAMPLE DIODE AUX These two images show the schentics of the circuit used for...

Страница 56: ...hasize this the results In Udc can be taken into a calculation software the dI dV value can be calculated mathematically and plotted together with R Udc in one diagram One finds a nice accordance betw...

Страница 57: ...ersa If both devices are operating on the same frequency the function GetLockinChannel 2 applied to device 2 detects the output amplitude of device 1 and vise versa Manual Anfatec PCI Lockin Amplifier...

Страница 58: ...t is centrally mounted to a screw with a 0 8 mm turn threat so that 25 turn end up to be 20 mm distance The operation frequency for this experiment is chosen to be 39 0625 kHz just high enough that th...

Страница 59: ...ows multiple access to DLL functions A DLL function call in SciLab looks like this call SetLockInFreq 10000 1 d out 1 1 1 d If several lockin devices are connected the function SetUsedDevice DeviceID...

Страница 60: ...lues 9 3 3 NETWORKANALYZER Network analyzers detect amplitude and phase of a signal in the frequency space and plot them in the Bode Plot whicha a double logarithmic scale for amplitude and frequency...

Страница 61: ...tigate I V and dI dV curves with a lockin amplifier Two graphs display In AUX and R AUX as result Fig 53 Shown the result one obtains if a diode is taken as device under test which is quite illustrati...

Страница 62: ...ce For position sensing of the cantilever a laser beam deflection detection with a position sensitive photo detector is employed A lock in amplifier analyses the detector signal at the cantilever reso...

Страница 63: ...ic functions one can expect a force between tip and sample at the frequency ref as well as at 2 ref Figure 59 confirms this prediction It shows the frequency spectrum of the cantilever oscillation wit...

Страница 64: ...s can still be set with the internal resolution Change of dynamic reserve from 120 dB wrong number to up to 135 dB achieved in lowest input range Remote Control the misleading statement that an Ethern...

Страница 65: ...efore no software file for the scaling is needed anymore 11 3 SOFTWARE REVISIONS 11 3 1 10TH APRIL 2008 VERSION 1 02 The whole software package has been reworked concerning the handling of the hardwar...

Страница 66: ...e Manager devmgmt msc After installing the driver the Lockin device should appear in the Windows Device Manager as Anfatec Measurement Interface Because of Microsoft s Windows security updates it s po...

Страница 67: ...l the x86 driver for 32 bit and the x64 for 64 bit windows This can be done in Windows 10 by right click on the inf file Install Manual Anfatec PCI Lockin Amplifier AMU2 4 Rev 1 10 dated 30 09 20 Page...

Страница 68: ...our bug report to mailbox anfatec de The bug report should contain a screenshot of the window after calling msinfo32 Windows Start type msinfo32 Enter If there is a driver problem send us the Error co...

Страница 69: ...Lockin exe First time the Lockin exe has to be started as Administrator to register the calibration parameters in the registry In case of the following warning after opening the application click More...

Страница 70: ...Manual Anfatec PCI Lockin Amplifier AMU2 4 Rev 1 10 dated 30 09 20 Page 70 70...

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