Multchannel Frequency Comparator VCH-315 User Gude
Table of contents 1 Introducton... 3 2 The workng prncple of the Comparator... 6 3 The computed functons... 8 3.1 Basc ratos... 8 3.2 Statstcal functons... 10 4 Installaton... 13 4.1 Installaton n Wndows... 13 4.2 Installaton n Lnux... 17 5 Connectng the Comparator and startng to work wth the Program... 19 6 Interface... 22 6.1 Current measurement graphs... 25 6.2 Man wndow menu... 30 6.3 Records fles... 32 2
1 Introducton Program "Multchannel frequency comparator" (the Program) s desgned to control the multchannel frequency comparator. The program provdes processng and keepng of the measurement results of the phase dfference, frequency dfference and frequency nstablty. Frequency comparator VCH-315 (the Comparator) s desgned to measure the relatve frequency dfference and frequency sgnals nstablty of the tme and frequency standards. It contans eght dentcal measurng channels and performs hgh precson phase and frequency comparson. Key applcatons - verfcaton of metrologcal parameters of precson frequency sgnals sources; - tme and frequency etalon systems; - computed control measustem; - scentfc research measurements. Communcaton between the IBM / PC-type computer, on whch the program s nstalled, and the comparator s performed va RS-232C nterface, USB or LAN nterface (Wndows only). Comparator supports only one connecton va RS-232C nterface, USB nterface or LAN nterface. Only one connecton s avalable va LAN nterface. The program requres Wndows XP, Vsta, 7, 8, 10 or Lnux operatng system wth kernel verson 2.6.x or hgher. 3
Implemented features: fles; recevng measurement data from the comparator, automatcally savng data n calculatng statstcal functons characterzng the frequency dfference between two sgnals; dsplayng measurement results and calculated functons n the form of charts on wndows nterface; prntng charts on a prnter connected to the computer. "Frequency comparator measurements processng program Analyser s ncluded wth the program. It has the followng features: smultaneous processng of the data across multple channels of the comparator, and the smultaneous processng of the data from several comparators (maxmum number of concurrent entres - 32); processng of the prevous measurements, and processng of the current measurement data wth automatc update of charts and statstcal characterstcs; a wde range of computed parameters (mean relatve frequency dfference and frequency drft by least-squares method, standard devaton, Allan devaton, Hadamard devaton, maxmum tme nterval error, tme nterval devaton, power spectral densty of phase and frequency nose). calculaton of the statstcal characterstcs wth overlap method; elmnaton of frequency drft; 4
the cross-correlaton processng that allows to reduce the nose level contrbuton of the comparator n the measurement of the frequency nstablty (wth approprate measurement scheme); the cross-correlaton processng that allows to evaluate the characterstcs of the frequency nstablty not only for pars of sgnals, but also for each sgnal ndvdually by the method of three oscllators; comparng tme-frequency measurements wth the parameters (temperature, humdty, etc.) measurements; Ths manual provdes a summary of the bascs of the Comparator, as well as the nstructons on how to use and confgure the Program. 5
2 The workng prncple of the Comparator Comparator contans eght dentcal blocks of sngle-channel phase comparators for measurng snusodal sgnals, sgnal processor unt wth RS-232C, USB and LAN nterfaces, power supply unt. Each sngle-channel comparator has one nput for the measurement sgnal and a reference nput and conssts of two modules: the relatve frequency dfference multpler provdng multpler K=10 6, and the tme stamp counter wth 10-nanosecond resoluton. Pulse sgnal F s taken from the output of the multpler unt, ts frequency (equal to about 1 Hz) carres nformaton about the frequency dfference between the compared sgnals f y and f x : F yx [Hz] = 1 + K(f y f x )/f x. (2.1.1) K s the coeffcent of frequency fluctuatons multplcaton, equal to10 6. B band of the fluctuaton frequency transmttance s 3 Hz. Pulse sgnals wth frequency determned by (2.1.1) are fed to the nput of the tme stamp counter (TSC). Sgnal t yx,,that carres nformaton on the phase dfference of sgnals f y and f x., s taken from the output of the TSC dgtzed wth 10-nanosecond resoluton. Dagram of processes n the TSC that explans the formaton and usage of the dgtzed phase dfference sgnal t yx, s gven n fgure 2.1. 6
F 0 F yx t yx, M=1 M=10 Fgure 2.1 Dagram of processes n the TSC explanng formaton of the dgtzed phase dfference sgnal t yx F 0 reference sgnal 1 PPS, generated from the heterodyne sgnal, "bound" by the PLL to the reference sgnal X. The comparator provdes smultaneous measurements of phase dfferences between the dfferent channels wth an accuracy of less than 10 ms. 7
3 The computed functons The program allows you to process measurement data n real tme and calculate the followng characterstcs: 1) mean relatve frequency dfference (between the sgnals fed to the fy (measured) and fx (reference) nputs of each comparator channel); 2) standard devaton - root mean square devaton of the measured relatve frequency value, calculated for the dfference between the frequences of the nput sgnals n each channel of the comparator; 3) Allan devaton - root mean square relatve two-sample devaton of the measured frequency value, calculated for the dfference between the frequences of the nput sgnals n each channel of the comparator; flter. 4) assessment of the current relatve frequency dfference usng the Kalman Standard devaton and Allan devaton are calculated for the measurement tme ntervals (samplngs): 1 s, 10 s, 100 s, 1000 s, 1 h, 10000 s, 1 day. Standard devaton and Allan devaton are calculated on the entre range of observaton tme (for all samples from measurement start). In addton, Allan devaton values can also be calculated n observaton tme ntervals T, fxed for each averagng nterval A (n the "sldng wndow" duraton T = N A, see. Secton 6.2). 3.1 Basc ratos The source for all the calculated statstcal functons are sgnals of the dgtzed phase dfference t yx, taken from the nputs of the "Tme stamp counter" (TSC) blocks, see Secton Ошибка! Источник ссылки не найден.. 8
Intally the phase dfference of sgnal pars s calculated (based on K - frequency fluctuatons multpler): yx, 1 t K. (3.1.1) yx, number of ntermedate count. The value Δyx, should correspond to the dfference between the phases of the sgnals fy and fx, and the measured value tyx, corresponds to the dfference between the phases of the sgnals fx and fy. Therefore t s a mnus sgn n the formula (3.1.1). The resultng value Δyx, can have a constant offset relatve to the actual phase dfference between the sgnals fy and fx. Then the relatve frequency dfference calculated for the pars of sgnals, measured on the nterval A = M seconds: 1 M y yx, yx, M ( 1) yx, M A. (3.1.2) Equaton (3.1.2) s the startng pont for the calculaton of Standard devaton and Allan devaton (formulas (3.2.1) and (3.2.2)), and also used to calculate mean relatve frequency dfference. The upper ndex M s further omtted, snce t s everywhere mpled that the frequency error s measured on the nterval M seconds. The Program also calculates the current varatons n the relatve frequency dfference: (3.1.3) yx, yyx, 1 yyx,, These varatons are used to calculate Standard devaton and Allan devaton. 9
3.2 Statstcal functons The mean-square devaton of the measured value of the relatve frequency (RMS) s calculated usng (3.1.2): N N y yx, y yx 1 2. (3.2.1) N 1 1 N the number of the frequency dfference counts y yx, for a certan averagng nterval τ A, y N yx the average value of the relatve frequency dfference on averagng nterval N τ A. Root mean square relatve two-sample devaton of the measured frequency value (Allan devaton) s calculated on base of (3.1.3): y 1 N 1 2( N 1) 1 2. (3.2.2) yx, Mean relatve frequency dfference s calculated by usng the equaton (3.1.2), ts value s dsplayed n the man wndow. In the calculaton n (3.1.2) averagng nterval concdes wth the whole tme of observaton n the respectve channel. The program evaluates the current relatve frequences dfference usng the Kalman flter. Ths estmate, along wth mean relatve frequency dfference estmate s dsplayed n the man wndow. The followng process model allows to take nto account the whte nose frequency and frequency random walk: 1 y, y1 y, 2 2 q1, q2, (3.2.3) 10
11 where Δ corresponds to the phase dfference, y corresponds to the estmated frequency dfference, ξ, η whte Gaussan nose, τ nterval between counts, equal to 1 s. Measurement model descrbes the measurement of the phase dfference:,, 2 R z (3.2.4) where ν whte Gaussan nose, z measured phase dfference. The flter parameters q 1, q 2, R are fxed at the moment, ther values can be changed n the n-fle of the Program. Default values are q 1 = 10-26, q 2 = 0, R = 10-24. Accordng to (3.2.) And (3.2.) parameter vector, transton matrx and the measurement matrx have the form of: y X, 1 0 1 F, 0 1 H. (3.2.5) The covarance matrx of the process nose has the form of: 2 2 2 2 2 3 2 1 2 2 3 q q q q q Q. (3.2.6) Durng ntalzaton of the Kalman flter assessment of the state vector X- and estmaton error matrx P- are gven. After that flter algorthm starts. Flter coeffcent s calculated: R H P H H P K T T. (3.2.7) Then the flter state s specfed: X H z K X X ˆ ˆ ˆ. (3.2.8) Error matrx s specfed:
P P I K H. (3.2.9) Predcton for the next step s mplemented: X F( ) Xˆ ˆ 1 (3.2.10) P T 1 F P F Q (3.2.11) The procedure s repeated, startng wth the calculaton of the formula (3.2.7). The desred estmate of the relatve frequency dfference at the teraton s the value y. 12
4 Installaton To use the Program you need at least Pentum-III wth at least 512 MB RAM. 4.1 Installaton n Wndows The program can work under Wndows XP, Vsta, 7, 8, 10. The software s nstalled from the CD (f CD s not ncluded n the product package, ask the manufacturer the nstallaton fle). Usually the nstallaton program starts automatcally. If t does not, run setup.exe from the root drectory of the CD-ROM manually. The nstaller wll create a "Comparator" shortcut on the desktop and the correspondng tem n the "Start" menu. Installng the devce va USB Before usng the USB nterface of the comparator to the computer you need to nstall devce drver that creates a vrtual seral port when the comparator s connected va USB. To nstall the drver and create a vrtual seral port connect the comparator to the computer USB port and turn t on. If the drver s already nstalled, the operatng system wll detect the new "USB Seral Port" devce, assgn t a number and dsplay a message, such as "USB Seral Port (COM8)", "Your new hardware s nstalled and ready to use": If there s no drver Wndows wll launch the New Hardware Found Wzard: Declne connecton to Wndows Update, then clck "Next" and select the settng "Install from a lst or specfc locaton". 13
As the drectory contanng the drver select the folder "Drver" on the CD-ROM wth comparator software (Fgure 4.4): If the warnng about software compatblty wth the operatng system "Wndows XP" appears, clck the Contnue Anyway button. After the drver nstallaton, clck "Fnsh" button. After the nstallaton of the drver the devce avalablty message wll appear on the screen. In some cases, the New Hardware Found Wzard starts agan. In ths case, you need to go through the nstallaton process agan. Installng the drver to connect the devce va LAN nterface For remote control va LAN you need to nstall specal software that comes on a dsk. Ths software s also avalable at the followng address: http://www.lantronx.com/devce-networkng/utltes-tools/com-port-redrector.html. To nstall run setup_cpr_x86x64cd_4.3.0.2.exe. After nstallaton, run the "CPR Manager" program (see. Fgure 4.1). Fgure 4.1 Locaton of the "CPR Manager" shortcut n the "All Programs" menu n Wndows 7 14
Fgure 4.2 "CPR Manager" man wndow Lst of the COM-ports wll be dsplayed. If all of them are marked as unavalable (Inaccessble) clck the "Add/Remove" and select an avalable number for the vrtual COM-port (Fgure 4.3). After that the new COM-port appears n the lst labeled "New" (Fgure 4.4). Clck "Search For Devce", after some tme the lst of avalable devces wll appear n the bottom of the table wndow (Fgure 4.4). Select the devce wth MACaddress (HW Address) that matches the MAC-address of the devce. Double-clck the left mouse button on the requred row of the table. IP-address of the devce wll be coped to the table n the Settngs tab for the new (selected) COM-port (Fgure 4.4). Clck "Save". The devce s ready for use va LAN nterface. 15
To ensure the successful settng up of the vrtual COM-port you can use the Wndows Devce Manager, t wll show created port, for example: Lantronx CPR Port (COM2), n "Ports (COM & LPT)" tab. Fgure 4.3 Vrtual COM-port selecton wndow (COM2 s selected) 16
Fgure 4.4 Selectng devce from the lst by ts MAC-address (only one devce shown here) 4.2 Installaton n Lnux To use the Program n Lnux copy VCH315 drectory from the CD ncluded n the product package to the local computer's dsk (or unzp the fle wth ths drectory when downloadng programs from the ste). If CD s not ncluded n the product package, ask the manufacturer the nstallaton fle. To start the Program run from the command lne fle "start.sh" from VCH315 drectory as follows:./start.sh The Program requres root access because t works wth computer ports. FTDI-drver for vrtual COM-port VCP s needed to work wth a comparator va USB. 17
Most Lnux dstrbutons wth kernel verson 2.6 and above have ths drver, so no setup s requred. Otherwse, the drver s avalable for download on the webaddress: http://www.ftdchp.com/drvers/vcp.htm. For RS-232 nterface connecton t s recommended to use the computer COM-port ntegrated on the motherboard, or use a specal USB-RS232 adapter from FTDI company. Otherwse operaton va COM-port to Lnux s not guaranteed. 18
5 Connectng the Comparator and startng to work wth the Program If the comparator s connected va RS-232 nterface, then before connectng the devce to the computer t s recommended to turn off the devce. If a USB nterface s used, the comparator can be connected n the ON state. After connectng the devce to a computer, you can turn the devce on. When you frst connect the devce va USB, you may need to nstall a drver (see Secton 4). After program started the man wndow and the wndow "Auto Connect..." showng the process of connectng wth the devce (see Fgure 5.1) wll appear. The "Auto connect..." wndow s dsplayed and the ports analyss process and devce connecton begn at startup f you select the "Analyse ports at every program start" tem n the "Auto connect..." or n the "Connectng to the devce" (menu tem "Optons> Connecton ", refer to Secton 6.2). The program automatcally searches for COM or USB ports on the computer wth connected comparators. If no comparator s not found, the program dsplays a message askng you to retry the connecton. If "Analyse ports at every program start" s not checked, then when you run the Program t wll attempt to connect usng COM-port number from the prevous program run, the number s stored n the n-fle n the Program drectory. 19
Fgure 5.1 Man wndow at startup Name of the man program wndow contans the name of the comparator and ts code (VCH-315). You can turn on the Comparator after the launch of the Program. If the program was able to detect connected Comparator, message "Connectng the comparator" (see Fgure 5.1) s dsplayed n the status bar. If communcaton wth the comparator was successful status bar wll show message contanng the connecton port number, for example: "The comparator s connected (COM1)". The feld n the upper rght corner of the man wndow changes colour to green, the label changes to "The comparator s connected". The comparator channels that contan measured and reference sgnals are marked green n the table n the man wndow, the correspondng table columns become actve (Fgure 5.2). 20
Fgure 5.2 Man wndow after connecton s establshed If multple comparators are connected, toy need to choose the comparator from the lst n the "Optons" menu under "Connecton" tem (see Secton 6.2). Next tme you start the Program connecton s establshed wth the comparator selected earler. 21
6 Interface Program nterface s standard for Wndows applcatons (Fgure 6.1). Appearance of the program may dffer from shown n ths manual dependng on the user's ndvdual settngs. The man element of the Program wndow s a table contanng nformaton on the sgnal n each channel, the number of counts obtaned, the average relatve frequency dfference, assessment of the current relatve frequency dfference, value of the frequency nstablty (standard devaton or Allan devaton). You can choose between showng ether standard devaton or Allan devaton n the table and graphs performed n "Settng calculatons" tem n "Optons" menu (see Secton 6.2). Fgure 6.1 Man Wndow To start or stop measurements n the requred channel clck on the correspondng feld n the "Start/Stop" row. If you want to start or stop measurements smultaneously 22
on all channels that contan sgnals use the buttons: "Start all channels", "Stop all channels." When you try to stop the measurement n one or all channels wndow appears, askng whether ths operaton should contnue. When you clck "Analyse records" program starts the tme-frequency measurement data processng that allows you to analyse both the current measurement data and prevous data. Entres for channels that are measured at the current tme are automatcally downloaded n the wndow. Ths entres are automatcally updated. The program allows you to specfy names for the reference and measured sgnals of each channel n the approprate felds n the "reference sgnal" and "measured sgnal" rows. The names of the sgnals must be assgned before the measurements start, after that edtng felds of the table wth the names of the sgnals wll not be possble. The names of the sgnals wll be dsplayed when workng wth the entres n the tme-frequency measurements data processng program. The text of the entre table or only the selecton can be coped to the clpboard, saved to a fle or prnted out. To do ths, press the rght mouse button on the table feld and select the requered opton n the pop-up menu (see Fgure 6.1). If the devce contanes one or more temperature sensors, addtonal channels for measurng temperature, hghlghted n orange, are avalable n the table of the man wndow (see Fgure 6.2). 23
Fgure 6.2 Man wndow. Temperature measurement channel (optonal) The nterval between the counts of temperature measurement s fxed at 10 s. Measurements n channel for temperature recordng start and stop same way as n the other channels. When you press the "Start all channels" / "Stop all channels" on avalable channels for temperature recordng the measures wll also the start (stop). You can change the name n the temperature felds of the channel. By default, the "reference sgnal" contans the strng "FMC" and the "measured sgnal" - the strng "Temperature N", where N s the number of the sensor. When measurements are runnng the feld "Number of counts" dsplays the number of obtaned temperature counts. The rest of the felds n the table for the channel reman empty. Smlarly to the phase dfference measurement the Program creates the current temperature graphs, as well as temperature varatons and the average temperature varaton dependence from the averagng nterval. The formulas for the calculatons 24
are the same as n the phase measurements processng, but temperature s used nstead of the phase dfference. 6.1 Current measurement graphs In "Plots" row of the table of the man wndow you can open the graphs of phase dfference, relatve frequency dfference, Standard devaton or Allan devaton by pressng the correspondng button. The program can show the decmated phase dfference values, and average values of the relatve frequency dfference on averagng ntervals of 1 s, 10 s, 100 s, 1000 s and 3600 s. To select the averagng nterval for the frequency or the decmaton factor for phase you need to press the rght mouse button n the requred channel feld n the "Plots" row, and select the tme nterval (see Fgure 6.3). Fgures 6.4 and 6.5 show examples of phase dfference and relatve frequency dfference graphs for averagng ntervals of 100 s and 1 s respectvely. Graphs show up to 1000 last entres for any averagng nterval. Lne of mean relatve frequency dfference can be dsplayed on the frequency graph (Fgure 6.5). The average value s calculated by formula (3.1.2) for the current graph. Ths value may vary sgnfcantly for frequency graphs wth dfferent averagng ntervals, and can also be dfferent from the value obtaned by the Kalman flter and shown n the table.. 25
Fgure 6.3 Man wndow. Selectng averagng nterval for the phase and frequency graphs 26
Fgure 6.4 Phase dfference graph for averagng nterval of 1 s 27
Fgure 6.5 Relatve frequency dfference graph for averagng nterval of 100 s 28
Fgure 6.6 Standard devaton graph Fgure 6.6 s an example of standard devaton graph, that also contans a table of standard devaton values. All graphs have a marker that appears when you clck left mouse button n the graph feld. Horzontal and vertcal values for the selected pont are shown n the upper rght corner of the wndow (Fgure 6.5). Wth a marker you can measure the dstance between two ponts on the graph, to do that select the frst pont by clckng left mouse button, then hold down the button, move cursor to the second pont and release mouse button. The measured horzontal and vertcal dfference values wll be dsplayed n the upper rght corner of the wndow (Fgure 6.4). Each graph wndow has the "Optons" menu, where you can save the graph to a "bmp" or "jpg" fle or prnt t out. 29
6.2 Man wndow menu Fgure 6.7 shows the "Optons" menu of the man wndow. The "Connecton" tem opens a "Connect devce" (Fgure 6.8) wndow. Ths wndow shows the lst of avalable COM-ports (ncludng vrtual COM-ports) of the computer. If the connecton to the devce s found n the lst, the correspondng COMport wll be hghlghted and the seral number of the connected comparator s shown. FIgure 6.7 "Optons" menu of the man wndow When you clck "Refresh and connect" button, f measurements are stopped the current devce connecton (f establshed) breaks and port analyss begns n order to fnd and connect to Comparator. If measurements are gong on ths opton s not avalable. When you clck "Apply" the Program wll try to connect to COM-port selected n the lst, f the number of the selected port s dfferent from the current one. Opton "Analyse ports at every program start" means that the analyss of ports and connecton to the devce, f t s detected (Secton 5), wll be made agan at the 30
next program start. If ths opton s selected, next tme you start connecton attempt wll be made at the prevously selected COM-port specfed n the n-fle. If PC runnng the program s connected to multple Comparators VCH-315 you can select the requred COM-port from the lst. Clck "Apply" to connect to the Comparator va the selected port. When you clck "Update and connect" current connecton to the devce (f t has been establshed) s broken, ports analyss and connecton to the prevously selected Comparator wll start.. Fgure 6.8 "Devce connecton" wndow Menu tem "Setup" (Fgure 6.7) opens a wndow "Frequency stablty characterstcs setup" (Fgure 6.9). You can select statstcal functons: SDEV (root mean square relatve devaton of the results of pars of sgnals frequency dfference measurements) and ADEV (root mean square relatve random two-sample devaton of the results of pars of sgnals frequency dfference measurements). SDEV (standard devaton) s always calculated at the entre nterval of observaton tme (snce start of measurements). ADEV (Allan devaton) can be calculated at the entre nterval of observaton tme or at a fxed nterval precedng the current moment (n a sldng wndow). If you select a fxed nterval you need to set the number of averages, e the length of the sldng wndow. The number of averages can be set from 32 to 1000. For example, f you select 100 averages the ADEV observaton tme at averagng nterval A = 1 wll be T = 100 s, and for A = 3600 s wll be T = 360000 s. 31
Note. If frequency jump occurred wth 100 averages selected then after 101 seconds ADEV value for A = 1 s wll not contan any nformaton about ths jump Note that the number of averages can be changed only when measurements on all channels are stopped. You can change the type of calculated functon durng measurements. After selectng the necessary statstcal functon press "Yes" or "Apply", then the changes wll take effect, the table and graphs wll show the values of selected characterstc. "Help" menu provdes nformaton about the program verson and frmware verson of the connected comparator. Fgure 6.9 "Frequency stablty characterstcs setup" wndow 6.3 Records fles Program saves phase dfferences samples measurement data. t yx, n two catalogs "samples" and "ASCII" n ts root folder. In the "samples" catalog data s stored n a format desgned for tme-frequency measurements data processng program. For each channel, two fles are created wth "*.nf" and "*.dat" extensons and named n YYMMDD_n format where YY - year, 32
MM - month, DD - day, n - channel number. If there were no measurements n a day, then fles for ths day are not created. Data processng program can be started by pressng the "Analyse" button n the man wndow (see Secton 6). In addton, the processng program can be run on another computer connected va LAN to the computer runnng the "Multchannel Frequency Comparator" program. In the processng program you need to specfy the path to the "samples" drectory to work wth records. "ASCII" catalog contans measurement data records n ASCII format for each channel separately. The fle name ncludes date and tme of recordng start: YYYYMMDD_hh_mm_ss_n, where YYYY - year, MM - month, DD - day, hh - hours, mm - mnutes, ss - seconds, n - channel number. Records are dvded nto fles for days. If recordng s contnued on the followng day, a new fle wth name that ncludes the date of the next day and tme 00:00:00 (eg 20150601_00_00_00_1) wll be created. The mage below shows an example of a fle n ASCII-format. The frst column contans tme of measurement correspondng to the tme of the computer that s runnng the program. The second column contans comparator tme counts n seconds. The thrd column contans comparator t yx,. counts. For phase dfference samples n seconds, you must dvde t yx, by fluctuatons of the comparator frequency multplcaton coeffcent K, equal to 10 6, and change the sgn (3.1.1) 33
Fgure 6.10 Example of the records stored n ASCII-format 34