TFG 2000系列 DDS 函数信号发生器简介
Contents
1. User s Manual DDS Function Generator 3 2 4 Format of amplitude value There are two ways to display and to enter the amplitude of channel A Press the key of pp rms to circularly select peak peak value or virtual value and the corresponding indicator light will be on The displayed value of the amplitude will vary with the different format Although there are two formats for amplitude values the working way inside the generator is Vpp Limited by the amplitude resolution a little difference will be produced between the former and the latter after exchanging Entering 1Vpp for sine wave for example the virtual value after changing is 0 353Vrms But entering virtual value of 0 353Vrms the Vpp after changing is 0 998Vpp Of course the difference is within the error range If the waveform is square the conversion coefficient is 2 Vrms is used only in the function of Tone and the waveform is sine or square For other functions or other waveforms only Vpp but not Vrms will be used 3 2 5 Amplitude attenuator The generator is set to Auto when startup or reset Press the keys of Attn and AU will be displayed Then the generator selects the attenuation proportion automatically according to the magnitude of the set amplitude The attenuation switches when the output amplitudes are 2Vpp 0 2Vpp and 0 02Vpp Now higher amplitude resolution and signal to noise can be obtained regardless of the magnitude of amplitude Th2. 3 2 Freguency of channel A Press the key of CH AJ to light the indicator lights of CHA and Tone The frequency value and the amplitude value of signal of channel A will be displayed and the waveform indicator light will display the waveform of channel A 3 2 1 Setting of frequency of channel A Press the key of Freq to display the current frequency value The frequency value can be entered either by the numeric keys or by the knob The signal of the frequency will be output at the end of CH A 3 2 2 Setting of period of channel A The signal of channel A can also be set and displayed in the form of period Press the key of Perd The current period value will be displayed Then use the numeric keys or the knob to enter the period value But frequency synthesizing way is still used in the interior of the generator It is only a conversion when entering and displaying the data Limited by the low end resolution of frequency only those frequency points with large distant period can be entered for longer periods Although the setting and display of the period are accurate the period values of real output signal will be greatly different The user should know fairly well 3 2 3 Setting of amplitude of channel A Press the key of Ampl and the current amplitude will be displayed Then use the numeric keys or the knob to enter the amplitude value The amplitude will be output at the end of Output A 23
3. 19 Chapter 3 Handling Instruction General operallon tile ers kees eos Seek Pe a Aa eyes eae reac 21 Frequency of channel A 7 23 Frequency channel B 28 Frequency sweeping 30 Frequency modulation FM 32 Exterior measurement 7 7 77 7 7 77 77 2727 ne 35 Parameter calibration 1 37 Parameter calibration 2 39 Chapter 4 Maintenance Fuse replacement TT TT 40 Adjustment and Calibration Tana aaa 40 Cleaning and decontamination 7 7 7 7 77 777777777777777777777777 41 User s Manual DDS Function Generator Chapter 5 Specifications Characteristics of output A 7 77 77 7 777 77 7777 7 777777 42 Characteristics of output B 7 77 7777 77 7 7 7 44 Output characteristics of SYNC 7 45 Frequency counto rasert senner nai inet KE renee aa d 45 USB Interface 45 General characteristics 46 User s Manual DDS Function Generator Chapter 1 Brief Introduction The front panel and Rear panel of DFG 8000 series DDS function generators are described i
4. H 325 D mm weight 3 kg Note Specifications are subject to change without notice 46 Seoul Office 2002 Seocho Hyundai Tower 1319 13 Seocho Dong Seocho Gu Seoul Korea Tel 822 3487 1199 Fax 822 3487 2299 A EZ DIGITAL The specifications are subject to change without notice
5. There is a port of FM Input on the rear panel which can import exterior modulation signals The frequency of exterior modulation signal should fit that of carrier signal The amplitude of exterior signal should be adjusted according to the requirements of frequency deviation modulation or depth of amplitude modulation The larger the amplitude of the exterior modulation signal the larger the frequency deviation modulation or depth of amplitude modulation A User s Manual DDS Function Generator When using exterior modulation the frequency deviation modulation should be set to be O and the interior modulation signal should be closed Otherwise the exterior modulation cannot work properly Similarly if using the interior modulation the value of Frequency deviation modulation should be set and the exterior modulation signal should be taken out Otherwise the operation of interior modulation cannot be normal 34 User s Manual DDS Function Generator 3 6 Exterior Measurement Press the key of Count to light up the indicator light of Count The generator can be used as a counter to measure the frequency of the external signal 3 6 1 Measuring of external frequency Press the key of Menu and the indicator light of Hz will be on The instrument will be in the state of frequency measuring Link the measured external signal from the Input of exterior measuring on the rear panel The measured
6. cymometer to measure the frequency of channel A At the same time modify the calibrating code by the knob The frequency of channel A will be changed until the accuracy is calibrated up to 10 3 7 4 Calibrating of frequency deviation modulation Pressing the key of Menu J the indicator lights of FM and Devia will be on The calibrating code of frequency deviation modulation will be displayed on the upper row Now the frequency of channel A is 2MHz and the frequency deviation modulation is 1 Use the modulation meter to measure the frequency deviation modulation At the same time modify the calibrating code by the knob The frequency deviation will be changed until the accuracy is calibrated up to 1 the frequency deviation is 20kHz 3 7 5 Calibrating of phase shift of channel B Press the key of Menu and light up the indicator lights of CHB and Phase The calibrating code of the phase shift of channel B will be displayed on the lower row on the screen The frequencies of channel A and B are 1MHz and the phase difference of the two channels is 0 the signals of the two channels are observed by double trace oscilloscope and the calibrating code can be modified by the knob at one time The phase difference of the two channels will be changed until it gets to 0 After the calibrating is over press the key of Menu and 1000 will be displayed on the upper row on the screen Input arbitrary wrong code except 1
7. frequency of output starts from the end frequency subtracting by frequency step restarts to sweep from the end frequency after it gets the start frequency To and fro sweeping 2 The frequency of output starts from the start frequency adding by frequency step restarts to sweep from the end frequency subtracting by frequency step after it gets the end frequency Press the key of Menu and select Sweeping mode the sequence number and the name of the current sweeping mode will be displayed The setting of sweeping mode can be carried by the numeric keys or adjusting of knob 3 4 4 Setting of interval time As the start frequency stop frequency and frequency step are settled the interval time for each frequency step can be decided by the requirement of sweeping velocity The shorter the interval is the faster the sweeping velocity is The longer the interval is the slower the sweeping velocity is But the real interval is the settled interval time plus the runtime of the control software When the interval time is short the runtime of software cannot be neglected because the difference is large between the real interval time and settled interval time Press the key of Menu to light the indicator of Interval the present interval time value will be displayed The setting of interval time can be carried by the numeric keys or adjusting of knob 31 User s Manual DDS Function Generator 3 5 Frequency modulation FM P
8. in the close state It is required to input the calibrating code The standard code 1000 can be input by the numeric keys and then press nJ So 1000 is displayed on the upper row meaning the calibrating function is in the open state now Then calibrate as follows 3 7 2 Calibrating of frequency of channel A In the state of calibration press Menu J to enable the indicator lights of CHA and Tone The calibrating code of frequency of channel A will be displayed on the upper row Now the frequency of channel A is 1MHz Use the cymometer with the accuracy of over six digit to measure the frequency of channel A At the same time modify the calibrating code by the knob The frequency of channel A will be changed until the accuracy is calibrated up to 10 Because the synthesizer of channel B and the synthesizer of channel A use the same fixed clock reference the frequency of channel B has the same accuracy as the frequency of channel A 3 7 3 Calibrating of carrier frequency In the frequency modulation carrier synthesizer uses controllable clock reference Although the carrier frequency is still the frequency of channel A it should be calibrated in addition Pressing the key of Menu J the indicator lights of FM 37 User s Manual DDS Function Generator and Carrier will be on The calibrating code of carrier frequency will be displayed on the upper row Now the frequency of carrier frequency is 1MHz Use the
9. will enter into the single frequency function of channel A Setting of frequency of channel A Set the frequency to be 3 5 kHz Freq 3 5 kHz Adjusting of frequency of channel A Press the key of lt or gt J to move the cursor In order to adjust the frequency finely or crudely turn the knob clockwise or anticlockwise to decrease or increase the number with continuous carry or borrow In this way other option data can also be adjusted by the knob which will not be restated again Setting of period of channel A Set the period to be 25ms Perd 21 5 ms Setting of amplitude of channel A Set the amplitude to be 3 2V LAmpl 343 J 2 V Selecting of amplitude format of channel A Virtual value or peak peak value pp rms The indicator light of Vpp means the selection of peak peak value of amplitude The indicator light of Vrms means the selection of virtual value of amplitude 12 User s Manual DDS Function Generator Selecting of common used waveforms of channel A Select sine square triangle ramp for channel A Sine Square Triang Ramp Selecting of waveform of channel A Select exponential for channel A waveform no 12 see the table of 16 waveform sequence numbers on page 19 Wave 1 2 n Setting of duty cycle of channel A Set the duty cycle of channel A to be 65 Duty 6 5 Setting of attenuation of channel A Set the fixed attenuation to be OdB select auto atte
10. 0 1MHz lt for frequency lt 10MHz 20 10MHz lt for frequency 20MHz Output impedance 500 5 1 4 Offset characteristics for the attenuation of OdB Offset range 10V Chigh impedance Resolution 20mV Offset accuracy 1 20mV 5 1 5 Sweeping characteristics linear frequency sweeping Sweeping range the start end point can be set arbitrarily Sweeping step any value greater than the resolution Sweeping rate 10ms 60s step Sweeping mode positive negative to and fro 5 1 6 Frequency modulation characteristics Carrier signal Channel A Modulation signal Interior signal of channel B or exterior signal Frequency deviation modulation 0 10 43 User s Manual DDS Function Generator 5 2 Characteristics of output B 5 2 1 Waveform characteristics The same as that of ChannelA 5 2 2 Frequency characteristics The same as that of ChannelA 5 2 3 Amplitude characteristics The same as that of ChannelA 5 2 4 Characteristics of harmonic wave The frequency of channel B is the harmonic of channel A Harmonic wave 0 1 250 0 times Frequency of harmonic wave lt 1MHz Phase difference of two channels O 360 Resolution 1 44 User s Manual DDS Function Generator 5 3 Output characteristics of SYNC 5 3 1 Waveform characteristics Square Rise Fall times20nS 5 3 2 Frequency characteristics The frequency of SYNC is the same as that of channel A when CHA is selected and it is the same as that of chan
11. 000 by the numeric keys and press the key of n The display on the upper row will be which means the calibrating is closed The calibrating code is stored in non losable memorizer so that they will not be lost even if the power is off Unless calibrating again will the calibrating code be renewed 38 User s Manual DDS Function Generator 3 8 Parameter calibration 2 The amplitude and offset cannot be calibrated via the keyboard If the error is too big the following calibrating method can be adopted 3 8 1 Calibration of amplitude of channel A Select the function of Frequency of channel A Select sine waveform with the frequency of 1kHz and the amplitude of 7Vrms Using the voltage meter with real virtual value measures the output AC voltage Micro potentiometer RP3 is used to calibrate output voltage to 740 02 Vrms 3 8 2 Calibration of offset of channel A Set the attenuation of channel A to be 00dB the amplitude to be OV the offset to be OV to measure the output DC voltage Use micro potentiometer RP7 to calibrate the zero point to OV 30mV Set the offset to be 10V to measure the output DC voltage Use micro potentiometer RP2 to calibrate the output voltage to 100 1 V 3 8 3 Calibration of amplitude of channel B Select the function of Frequency of channel B The waveform of channel B uses sine with the frequency of 1kHz and the amplitude of 7Vrms using the voltage meter with real virtua
12. DFG 8000 Series DFG 8020 8010 8005 DDS Function Generator User s Manual CA 3 x W Pa GC Lan an S Q Th 3 EZ DIGITAL User s Manual DDS Function Generator Introduction of DFG 8000 Series DDS Function Generators The present guide is valid for all models of DFG 8000 series DDS function generators DFG 80xx The last two digits of 80xx stand for the maximum frequency MHz for the model of a specified one With Direct Digital Synthesis Technique DDS DFG 8000 series DDS function generators are of the high performance indexes and numerous function characteristics which are necessary for the fast completion of measuring The simple and clear front panel design and the display interface of number and indicator light are convenient for the users to operate and observe Moreover the extended optional functions enhance the system characteristics The generators are of the following advanced specifications and powerful function characteristics High frequency accuracy up to the level of 10 High frequency resolution 20MHz for the whole range Unlimited measurement range without limitation for the whole range digital setting directly Non intergraded process up to the stable value immediately when switching continuous signal phase and amplitude without deflection High waveform accuracy the output waveform is synthesized by the computation value of functions with higher w
13. R 1 Display screen 2 Power switch 3 Waveform selection keys 4 Option key 5 Output A 6 Output B 7 Synchronization 8 Direction keys 9 Adjusting knob 10 Function and numeric keys 11 USB interface User s Manual DDS Function Generator Rear Panel gt REPLACE FUSE AS SPECIFIED DISCONNECT POWER CORD BEFORE REPLACING FUSE AC115 230 50 60Hz 30VA MAX 1 AC power socket 2 Input of count 3 Input of AM 1 3 Screen description There are two rows of display on the screen The parameters of time such as frequency period interval gate time frequency deviation modulation duty cycle and others are shown on the upper row The parameters of voltage such as amplitude offset attenuation as well as other parameters such as harmonic times phase difference waveform sequence number and so on are shown on the lower row There are 22 indicator lights on the screen indicating output channels signal waveforms the current function and options as well as the units of the parameters The instrument has 5 functions with the following different options User s Manual DDS Function Generator The options with shadow in the following table are the common ones which can be selected directly by pressing the corresponding keys on the front panel and the instrument will enter into the function of these options automatic
14. Summarize The basic working principle of the generator is described in chapter two Handling Instruction The function operation and an application of the generator are described in detail in chapter three Service and Technical Support The warranty and technique support of the product are introduced in chapter four Specifications The performances and technical specifications of the function generator are introduced in detail in chapter five Notice Please excuse any modification of the contents without special notification Besides it is unavoidable for not so adequate description and wrong printing The present document will not warrant in any form including but not limited to those for special aims User s Manual Table of Contents Chapter 1 Brief Introduction DDS Function Generator Prepare to se San naka aa Dem aan a a ccc aa aaa a 7 Description of Front Panel and Rear Panel 8 Screen description rr rr rrr rrr rr rrr crc rrr rrr 9 Keyboard description 7 11 Basic operation 12 Chapter 2 Principle Summarize Principle frame 17 Working principle of DDS gt gt gt 70 rrr rrr rrr rrr rr rrr ccc rrr 18 Working principle of operation control
15. ally The options without shadow are uncommon used So it is required to select the corresponding function firstly and then select different terms circularly by Menu Table of function option i Frequency of Frequency of Exterior ngo channel A channel B Fragueney ah aba measuring n sine sine sweeping modulation frequency Frequency of Frequency of Start Carrier ne CHA CHB frequency frequency frequency Period of Period of End Carrier f Gate time CHA CH B frequency amplitude Amplitude of Amplitude of Step Frequency CHA CHB frequency modulation ffset of Waveform of Waveform of Sweeping KEN l CHA CHB mode arn tne option modulation Duty cycle of Duty cycle Interval Modulation CHA of CHB time waveform Attenuation of Attenuation of CHA CHB H A a WA a HA 2 CH B Step Phase shift frequency of CH B Step amplitude 10 User s Manual DDS Function Generator 1 4 Keyboard description There are 38 keys on the front panel of the instrument with the following functions see the layout of the front panel 07 1 2 3 4 5 6 7 8 9 are used to input numbers is used to input Decimal point is to enter the minus in the option of Offset and in other circumstances it is used to enable or disable the key press sound circularly CHA CHB Sweep FMJ Count are the Function selection keys Menu J is to select the o
16. aveform accuracy and less distortion Multi waveform 16 types of waveforms can be output Square characteristics Accurate square duty cycle can be set Output characteristics Independent output for two channels the phase difference can be set accurately Frequency sweeping Be of the function of frequency sweeping and amplitude sweeping Start point and end point can be set arbitrarily Frequency modulation Frequency modulation signal FM can be output Computation function Frequency or period amplitude virtual value or peak peak value can be selected User s Manual DDS Function Generator Operation mode Keyboard operation color large screen menu display direct digital setting or continuous adjusting by knobs High reliability The adopting of Large Scale Integration circuit SMT and VFD make the generator high reliability and long service life Frequency measuring Frequency Counter can be selected to measure the frequency of external signal up to 100MHz 6 Programmable interface The USB interfacing is available DFG 8000 series DDS function generators and accessories package list DDS function generator Power cord 09 testing cable User s Manual in CD R USB interface cable 1 1 1 Q9 bi nip wire 1 1 1 Compact Disc of USB Interface 1 User s Manual DDS Function Generator Summary of User s Guide Book Brief Introduction The brief usage of the generator is introduced in chapter one Principle
17. e circuit When the key is pressed MPU identifies the code of pressed key and then executes the corresponding commands Display circuit displays the working state and parameters of the generator using menu characters The knob on the panel can be used to change the number in the position of cursor A trigger pulse will be generated for each rotating of 15 MPU can judge whether the rotation is left or right If it is left the number in the position of cursor will be subtracted by 1 if it is right the number in the position of cursor will be added by 1 with continuous carry or borrow 19 User s Manual DDS Function Generator Chapter 3 Handling instruction General operation rule Frequency of channel A Frequency of channel B Frequency sweeping Frequency modulation FM gt Exterior measurement Parameter calibration 20 User s Manual DDS Function Generator 3 1 General operation rule 3 1 1 Data input If an item is selected the parameter value can be entered by ten numeric keys writing from left to right If there are more than one decimal point entered in a parameter only the first one is valid For the function of Offset minus can be entered To make the data come into effect unit key must be entered after data input For wrong data input there are two ways to modify If the output end permits wrong output signal press any unit key to end and then re enter data If the output end does n
18. e distortion of waveform is smaller But a little instant jumping will occur for output signal when attenuation switching which is not allowed in some cases So the fixed attenuation way is set for the generator Pressing the key of Attn the attenuation value can be entered by the numeric keys The attenuation is 0dB when the data entered lt 20 20dB when the data entered 220 40dB when the data entered240 60dB when the data entered26 and auto when the data entered280 The knob can also be used to adjust the attenuation The attenuation will change one gear for each step If the fixed attenuation way is selected the attenuation step will not be changed when the amplitude of signal changes So that the output signal within the whole amplitude range will be changed continually But if amplitude of signal is small in the attenuation of OdB the distortion of waveform will be larger and the signal to noise ratio is worse 24 User s Manual DDS Function Generator 3 2 6 Output load The setting value of amplitude is calibrated when the output end is open The real voltage of output load is the setting value of amplitude multiplied by the assignment ratio of load resistance and output resistance The output resistance is about 50Q When the load resistance is big enough the assignment ratio approaches to 1 The voltage loss of output resistance can be neglected The real voltage approaches to the setting value of amplitude But when the l
19. e of the signals of two channels can be entered by the numeric keys or by the knob The maximum resolution of time difference of the signals of two channels is 80ns so the resolution of phase difference is higher when the frequency is lower 28 User s Manual DDS Function Generator For example the resolution of the phase difference is 1 when the frequency is lower than 34KHz The higher the frequency is the lower the resolution of the phase difference is For example the resolution of the phase difference is 28 8 when the frequency is 1MHz Linking the signals of two channels to the oscilloscope setting the harmonic times and phase difference of the signals of two channels various stable Lissajous figures can be obtained 29 User s Manual DDS Function Generator 3 4 Freguency sweeping Press the keys of Sweep to light the indicate light of Sweep and select the function of Sweep The frequency sweeping signal can be output from the end of CHA The sweeping of output frequency adopts step mode The output frequency will be added or subtracted automatically by a step every other interval time The start frequency the end frequency the step frequency and the interval time are settled by operator 3 4 1 Setting of start point and stop point The start point of the frequency sweeping is the start frequency and the end point of the frequency sweeping is the end frequency Press the key of Menu to sel
20. ect Start the start frequency value will be displayed The setting of start frequency can be carried by the numeric keys or knob Press the key of Menu to select Stop the stop frequency value will be displayed The setting of stop frequency can be carried by the numeric keys or adjusting of knob It must be paid attention that the end frequency should be greater than start frequency Otherwise the sweeping cannot be carried 3 4 2 Setting of frequency step Since the start frequency and end frequency have been set the frequency step will be decided according to the measuring degree The larger the frequency step the less the points of frequency in one sweeping process the rougher the measuring but the required time is shorter The smaller the frequency step the more the points of frequency in one sweeping process the finer the measuring but the required time is longer Press the key of Menu to light the indicator of Step The step frequency value will be displayed The setting of frequency step can be carried by the numeric keys or adjusted by the knob 30 User s Manual DDS Function Generator 3 4 3 Selection of sweeping mode There are three frequency sweeping modes expressed in 0 1 and 2 Positive sweeping 0 The frequency of output starts from the start frequency adding by frequency step restarts to sweep from the start frequency after it gets the end frequency Negative sweeping 1 The
21. ere water or air could enter into the instrument while drying 4 User s Manual DDS Function Generator Chapter 5 Specifications Characteristics of output A Characteristics of output B Output characteristics of SYNC Frequency Counter General characteristic 5 1 Characteristics of output A 5 1 1 Waveform characteristics Waveform types 16 types including sine square triangle ramp and so on Waveform length 1 024 points Sampling rate 100 MSa s Amplitude resolution 8 bits Harmonic distortion 240dBc lt 1MHz 235dBc 1MHz 10MHZz 230dBc 10MHz 20MHz Total distortion lt 1 20Hz 200kHz 2200mVrms gt Pulse square rise fall time lt 35ns over pulse lt 10 Duty cycle 1 99 5 1 2 Frequency characteristics Frequency range sine 20mHz upper limitation corresponding to the model Others 20mHz 1MHz Resolution 20mHz Frequency accuracy 5x10 20 MHz Frequency stability 5x10 3hrs 42 User s Manual DDS Function Generator 5 1 3 Amplitude characteristics Amplitude range 2mVpp 20Vpp High impedance for frequency lt 10MHz 2mVpp 10Vpp High impedance for frequency gt 10MHz 15MHz 2mVpp 8Vpp High impedance for frequency gt 15MHz Resolution 20mVpp for amplitude gt 2V 2mVpp for amplitude lt 2V Amplitude accuracy 1 2mV high impedance virtual value freq is 1kHz gt Amplitude stability 0 5 3hrs Amplitude flatness 5 for frequencys1MHz 1
22. hase increment on the present result of phase accumulator in each sampling clock period so as to change the output frequency value by change phase increment According to the address from the phase accumulator take the quantized data out from the wave memorizer and then convert it into analog voltage via digit analog converter and operation amplifier Since the waveform data are discontinuous sampling stair sine waveform is output from DDS generator The included high level harmonic wave should be filtered by low pass filter so to output a continuous sine wave With high accurate reference voltage source in digit analog converter the output waveform is if high amplitude accuracy and stability Amplitude controller is a digit analog converter Based on the amplitude value preset by user it generates a corresponding analog voltage and then multiplied by the output signal so to guarantee the amplitude of output signal to be the preset value Offset controller is a digit analog converter Based on the offset value preset by user it generates a corresponding analog voltage and then added with the output signal so to guarantee the offset of output signal to be the preset value The synthesized signal from amplitude and offset controllers is amplified by the power amplifier and then is output from output end A 18 User s Manual DDS Function Generator 2 3 Working principle of operation control MPU controls keyboard and display parts by interfac
23. l value measures the output AC voltage Micro potentiometer RP7 is used to calibrate output voltage to 7 07 0 07 Vrms 39 User s Manual DDS Function Generator Chapter 4 Maintenance Fuse replacement Adjust and calibration Cleaning and decontamination CAUTION IT IS ESSENTIAL FOR SAFETY TO PROPERLY MAINTAIN AND SERVICE THIS INSTRUMENT WARNING VOLTAGES WITHNIN THIS INSTRUMENT ARE SUFFICIENTLY HIGH TO ENDANGER LIFE COVERS MUST NOT BE REMOVED EXCEPT BY PERSONS QUALIFIED AND AUTHORIZED TO DO SO AND THESE PERSONS SHOULD ALWAYS TAKE EXTREAME CARE ONCE THE COVERS HAVE BEEN REMOVED 4 1 Fuse replacement Disconnect and remove all connection from any live power source Unscrew fuse holder by screw driver Locate the defective fuse and remove it by gentling pulling out Install a new fuse of the SAME SIZE AND RATING Screwing fuse holder CAUTION MAKE SURE THAT THE RATED AND SPECIFIED FUSE ARE USED FOR REPLACEMENT 4 2 Adjustment and calibration It s recommendable to regularly adjust and calibrate this instrument Qualified and authorized personnel only should execute performance and procedure 40 User s Manual DDS Function Generator 4 3 Cleaning and decontamination The instrument can be cleaned with a soft cloth to remove any oil grease or grime Never use liquid solvents or detergents If the instrument gets wet for any reason dry the instrument using low pressure cleans wh
24. n this chapter so as to help users to master the usage as quickly s possible The main contents of the chapter are as follows Prepare to use Front Panel and Rear Panel Screen Description Keyboard Description Basic Operation User s Manual DDS Function Generator 1 1 Prepare to use 1 1 1 To check the instrument and the accessories Check whether the instrument and the accessories are complete and unbroken If the package is badly damaged please keep it until the instrument passes the performance testing 1 1 2 Plug in and turn on the function generator To guarantee the safe operation of the instrument the following conditions should be achieved Voltage AC115 230 145 V Frequency 50 145 Hz Power lt 30VA Temperature 0 40C Humidity 80 Plug the power connector into 220V socket outlet with safe earth wire Press the power switch on the front panel to switch on the power Now the initialization of the generator begins and then the default parameters are installed The instrument will enter into the working state of single frequency of channel A and output sine waveform and display the frequency value and amplitude value of signal of channel A Warning In order to ensure the security of the operator triple core socket outlet with safe earth wire must be used User s Manual DDS Function Generator 1 2 Description of Front Panel and Rear Panel Front Panel DDS FUNCTION GENERATO
25. nel B when CHB is selected When sweep is selected SYNC is high level at the beginning of the sweeping interval and it is low level in the middle of the sweeping interval The frequency of SYNC is the same as that of channel B when FM is selected 5 3 3 Amplitude characteristics Compatibility of TTL CMOS Low level lt 0 3V high level gt 4V 5 4 Frequency counter Frequency measurement range 1Hz 100MHz Display 8 digit LED display Gate time Hz Resolution 0 1Hz lt 10MHz 1Hz 10MHz2 Accuracy 0 5 count lt 500KHz Timebase Error 1count 2500KHz Time base 10MHz 50ppm Amplitude of input signal 200mVpp 20Vpp Input sensitivity 1Hz 10Hz 200mVpp 2Vpp 10Hz 100Hz 200mVpp 4Vpp 100HzZ 10MHz 200mVpp 10Vpp 5 5 USB Interface For details see the instruction of demonstration software 45 User s Manual DDS Function Generator 5 6 General characteristics 5 6 1 Power conditions Voltage AC115 230V 45 Frequency 50 60H Power lt 30W Fuse 2A 250V T type 5 6 2 Environment conditions Temperature 0 40 Humidity lt 80 5 6 3 Operation characteristics Keyboard operation continuous adjusted by digit knobs 5 6 4 Display mode Digit displays the working parameters Indicator light displays the function and option 5 6 5 Safety Insulation Category Portable equipment of local level Pollution degree 2 Protection to IEC 529 Ordinary 5 6 6 Dimension and weight Dimension 254 W x103
26. nuation AU after start up or reset Atten 0 dB Setting of offset of channel A Set the DC offset to be 1V when the attenuation is OdB Lofts 1 V Step frequency of channel A Set the step frequency of channel A to be 12 5Hz Press the key of Menu and press the keys of 17 2J 5 Hz The frequency of channel A will be added by 12 5Hz at each pressing of the key of AJ the frequency of channel A will be reduced by 12 5Hz at each pressing of the key of VJ 1 5 2 Setting of parameters of channel B Press the key of CHB 7J and the indicator lights of CHB and Tone will be on and select the function of Tone The setting method of frequency period amplitude Vpp Vrms waveform duty cycle of channel B is the same as those of channel A Setting of harmonic waveform of channel B Set the frequency of channel B is the once harmonic waveform of channel A 13 User s Manual DDS Function Generator Harmo 1 n Phase shift of channel B Set the phase difference between the two channels is 90 Phase 9 0 1 5 3 Frequency sweeping of channel A Press the key of Sweep Sweeping signal is output from channel A Use default parameters Setting of sweeping mode Set the sweeping mode to be to and fro Press the key of Menu J to light the indicator light of Sweep and then press 2 n Setting of other parameters is described in 3 4 1 5 4 Frequency modulation
27. oad resistance is smaller the voltage loss of output resistance cannot be neglected It should be paid more attention that the real voltage does not accord with the setting value of amplitude Output of channel A has over voltage protection and over current protection Several minute short circuit or reverse voltage of less than 30V will not lead to any obvious damage Nevertheless the above cases should be avoided in case of potential damage for the generator 3 2 7 Flatness of amplitude For the output frequency less than 1MHz the amplitude of output signal is very flat For the output frequency greater than 10MHz the matching characteristics of output amplitude and load will lead to the worse flatness The maximum output flatness will be limited too Generally speaking the maximum output flatness is 10Vpp for output frequency from 10MHz to 15MHz and 8Vpp for output frequency higher than 15MHz The larger the output amplitude is the bigger the distortion of the waveform is 3 2 8 Setting of offset of channel A In some cases certain DC component should be contained in the AC signal to be output so as to produce DC offset Press the key of Offs J and select Offset The present offset value of channel A will be displayed Use the numeric keys or the knob to enter the offset value The preset DC offset will be produced from the output of channel A 25 User s Manual DDS Function Generator It must be paid attention that
28. of channel A Pressing the key of FMJ the signal of frequency modulation FM is output from channel A The default parameters are used Setting of frequency deviation modulation Set the frequency deviation modulation to be 5 Press the key of Menu to light the indicator light of Devia Press the keys of 5 The setting of other frequency deviation modulation parameters will be described in 3 5 1 5 5 Initialization or reset state The initial working state after start up or resetting by pressing the key of Reset is as following Waveform of channel A and channel B sine Frequency of channel A and channel B 1kHz Amplitude of channel A and channel B 1Vpp Attenuation of channel A and channel B AUTO 14 User s Manual DDS Function Generator Duty cycle of channel A and channel B 50 Attenuation of channel A AU automatic Offset of channel A OV Harmonic waveform of channel B 1 0 Phase shift of channel B 0 Start frequency 100Hz End frequency 1kHz Step frequency 10Hz Interval time 10ms Sweeping mode 0 positive Carrier frequency 5OkHz Carrier amplitude 1Vpp Frequency modulation 1kHz Frequency deviation modulation 5 0 Modulating waveform sine Gate time 1000ms 1 5 User s Manual DDS Function Generator Chapter 2 Principle summarize In the present chapter users will acquaint with the basic concept of the signal forming and the interior operation of the generator so a
29. on Generator 3 6 3 Low pass filter If the measured frequency is lower and high frequency noise is included in the measuring of the external signal there will be the effect of trigger error resulted from the noise The measured result will be less accurate with unstable measured data The low pass filter with the frequency of 10kHz will be added to the input signal The high frequency noise in the filtering signal does not affect the low frequency signal the measured result will be more accurate If the frequency of measured signal is higher low pass filter will induce amplitude attenuation for the input signal so as that the measuring sensibility will fall More badly correct measuring result cannot be obtained The low pass filter should be taken out For the square signal with low frequency the low pass filter is not needed because that the trigger edge is steep and the trigger error is little 36 User s Manual DDS Function Generator 3 7 Parameter calibration 1 The parameter errors in specification are the indexes when leaving factory It is possible to increase for long time using and large temperature changing In precision measurement the generator should be calibrated The four parameters of the instrument can be calibrated in software calibration by the function of calibration 3 7 1 Code calibrating Pressing the key of Menu so as to display on the upper row of the screen which means the calibration is
30. ot permit wrong output signal re select the same item and enter correct data and then press unit key to end it The input of data can use any assorted decimal point and unit but the generator will display it in fixed format For example the data 1 5kHz or 1 500Hz entered will be effective displayed as 1 500 00Hz Take the unit key as the ending of a data entering The corresponding unit Hz V ms or dB will be displayed No display for other units 3 1 2 Step entering method In practice a group of equidistant frequencies or amplitudes is needed It will be a messy job to use numeric key entering method Using knob will be also inconvenient as the distant value is multi digit It can be easily reached by step entering method To simplify the operation the step function for the frequency and amplitude of channel A is set By the simple step key the frequency or the amplitude can be added or subtracted a step Besides the changed frequency will come into effect at once without pressing the unit key To generate a series of frequencies with the distant of 12 5kHz for example the sequence of pressing is as follows Press the key of Menu to select Step press the keys of 1 2 5 kHz The frequency of channel A will be added by 12 5Hz at each pressing of the key of 7 and the frequency of channel A will be reduced 21 User s Manual DDS Function Generator by 12 5Hz at each pressing of the key of VJ No
31. ptions without shadow in the table of function options circularly Freq Perd Ampl Atten Offs Duty Harmo Phase keys are to select the options with shadow in the table of function options directly pp rms 4 is to select the Peak peak 8 Virtual value of the amplitude circularly Sine Square Triang Ramp Arb are the waveform selection keys Press the former four keys to select the four common waveforms Pres Arb key to select one of the 16 waveforms using the waveform sequence number The above five keys are bi functional keys They also have the functions of units MHz kHz Hz mHz 6 and waveform sequence number nJ lf pressing the five keys after data input the units of the data will be selected so as to be the end of the data input AJ Vv are used to increase or decrease the frequency or the amplitude stepping of channel A lt gt are used to move the cursor leftwards or rightwards Cal J is used to calibrate the parameters Reset is used to restore the system l User s Manual DDS Function Generator 1 5 Basic operation The following description will explain the basic operation to meet the usual need of the users Every user whoever has questions should read the corresponding contents in the chapter three of the instruction 1 5 1 Setting of parameters of channel A Press the key of CHAJ to light the indicator lights of CHA and Tone and the instrument
32. quence number of the present waveform will be displayed The sequence number can be entered by the numeric keys and press the key of nJ to select the required waveform It can also be changed by the knob conveniently For the four common used waveforms press the keys of Sine Square Triang RampJ to select directly The sequence numbers and names of the 16 waveforms are shown in the following table 26 User s Manual DDS Function Generator List of names and sequence numbers of 16 waveforms sequenc sequence waveform name e waveform name number number 00 sine Sine 08 positive DC Pos DC 01 square Square 09 negative DC Neg DC 02 triangle Triangle 10 laba Ws All sine commuting 03 up ramp Up ramp 11 limit sine Limit sine 04 down Down 12 square root Exponent ramp ramp function 05 positive Pos pulse 13 logarithm Logarithm pulse function 06 negative Neg pulse 14 Half round Half round pulse function 3 2 11 Setting of duty cycle of channel A Press the key of Duty and the channel selects square automatically The duty cycle is displayed The value can be entered by the numeric keys or by the knob The square with set duty cycle will be output The adjusting range of duty cycle is 1 99 27 User s Manual DDS Function Generator 3 3 Freguency of channel B Press the key of CHB to select the function of Tone of channel B The sequence number and name of wa
33. ress the key of FM to light the indicator light of FM The instrument will be in the function of FM and the signal of frequency modulation will be output from the end of CHA 3 5 1 Setting of carrier frequency Press the key of Menu and light the indicator of Carrier the carrier frequency will be displayed The setting of carrier frequency can be carried by the numeric keys or adjusting of knob In frequency modulation the signal of channel A is taken as carrier signal and the carrier frequency is in fact the frequency of channel A But for the clock signal of DDS synthesizer is switched from fixed clock reference to controllable clock reference the frequency accuracy and stability of carrier wave will be reduced The maximum carrier frequency can reach to 5MHz only 3 5 2 Setting of amplitude of carrier waveform Press the key of Menu to light up the indicator light of Carrier and the value of amplitude of carrier waveform will be displayed The setting of carrier frequency can be set by the numeric keys or adjusting of knob 3 5 3 Setting of frequency deviation modulation Press the key of Menu to light up the indicator light of Devia the offset value of frequency modulation will be displayed The setting of frequency deviation modulation can be carried by the numeric keys or adjusting of knob The frequency deviation modulation stands for the change of carrier frequency in the frequency mod
34. s to know more about the specifications and use the generator in the best way e Principle frame Working principle of DDS 6 Working principle of operation control 16 User s Manual DDS Function Generator 2 1 Principle frame Keyboard Displayer Knob Modulation input DDS Amplitud eae Voltage Power and AM amplification amplification Offset setting Output protection control amplification Output attenuation 20 60dB l7 User s Manual DDS Function Generator 2 2 Working principle of DDS To generate a voltage signal the traditional analog signal source adopts electronic components as oscillator in different ways So both frequency accuracy and stability are not high enough Besides it is of the disadvantages of complicated technique low resolution and inconvenient frequency setting and realization of computer control Direct Digital Synthesize DDS technique is a new developing method of generating signals without any oscillator components by which a series of data stream are generated using digital synthesizing method and then a pre established analog signal is generated from digital analog converter To generate a sine signal for example the function of y sinx18should be digitally quantized first and then taking x as the address and y as the quantized data to store them into waveform memorizer DDS uses phase adding technique to control the address of waveform memorizer Add a p
35. signal can be periodic signal of arbitrary waveform The Vpp of the signal should be greater than 100mVpp but less than 20Vpp As the result includes the effect of crystal oscillating error and triggering error the accuracy will be a little worse than those in self testing Linking the end of channel A and the port of Count Input on the rear panel the generator can measure the frequency for the signal of channel A Entering the frequency by the numeric keys or by the knob the measured result can be displayed As the frequency synthesizer of channel A and frequency measuring instrument use a same clock the result measured does not include the effect of crystal oscillation error So the measured result is of high accuracy 3 6 2 Setting of gate time Press the key of Menu to light up the indicator light of Gate The gate time will be displayed The gate time can be entered by the numeric keys or by the knob For frequency measuring the method of averaging the periods is used So the longer the gate time is the more the collected periods is the more the effective digits for the measured result but the slower the tracking velocity of frequency changes Contrarily the shorter the strobe time is the less the effective digits for the measured result but the faster the tracking velocity of frequency change The latter setting is appropriate to measure the time stability of frequency in short time 35 User s Manual DDS Functi
36. the summation of the half of the output amplitude of signal and the absolute offset value should be less than 10V to guarantee the peak value of signal less than 10V Otherwise the amplitude limited distortion will be induced Besides when the attenuation of channel A is selected auto the output offset will attenuate with the attenuation of amplitude For the Vpp of amplitude greater than 2V the real output offset is the set offset value For the Vpp of amplitude greater than 0 2V but less than 2V the real output offset is tenth of the set offset value For the Vpp of amplitude less than 0 2V the real output offset is one percent of the set offset value It will be more convenient using the numeric keys than the knob when adjusting DC offset for output signal In general case whether DC offset is positive or negative DC level will rise if turning right and fall if turning left Sign of positive and negative will change automatically when passing through zero point 3 2 9 Output of DC voltage If amplitude attenuation of channel A is set to be 0 dB the output offset value is equal to the preset offset value and it is independent of the amplitude If the amplitude is set to be OV the offset can be set arbitrarily within the range of 10V The instrument will be a DC voltage source and preset DC voltage signal can be output 3 2 10 Selection of waveform of channel A There are 16 waveforms in channel A Press the key of Wave and the se
37. ulation process expressed as following DEVI 100xSHIFT PERD 32 User s Manual DDS Function Generator Where DEVI is the frequency deviation modulation SHIFT is the maximum single peak change value in frequency modulation PERD is the period value when the frequency deviation modulation is 0 In practice the offset value of frequency modulation is under 5 in order to limit the bandwidth taken by the carrier signal 3 5 4 Setting of frequency modulation Press the key of Menu and light up the indicator light of FM the value of frequency modulation will be displayed The setting of the value of frequency modulation can be set by the numeric keys or adjusting of knob In frequency modulation the signal of channel B is taken as modulation signal and the modulation frequency is in fact the frequency of channel B Generally speaking carrier frequency should be 10 times higher than modulation frequency 3 5 5 Setting of modulation waveform Since the signal of channel B is taken as the modulation signal the modulation waveform is in fact the waveform of channel B Press the key of Menu and light up the indicator light of FMfreq The sequence number and the name of the waveform of channel B will be displayed The setting of modulation waveform can be carried by entering the sequence number by the numeric keys or adjusting of knob 3 5 6 Exterior modulation Frequency modulation uses exterior modulation signals
38. veform of channel B will be displayed on the top left of the screen The setting method of frequency period amplitude Vpp Vrms waveform duty cycle of channel B is the same as those of channel A except that there is no DC offset for channel B 3 3 1 Setting of harmonic wave of channel B The frequency of channel B can be set and displayed at the multiple of the frequency of channel A That is to say the signal of channel B is the N grade harmonic wave of that of channel A Press the key of Harmo to select Harmonic of channel B The grade of harmonic wave can be entered by the numeric keys or by the knob The phases of the two channels can get the stable synchronously If Harmonic of channel B is not selected the signals of two channels will not keep harmonic relation at all Even the frequency of channel B is set to be the multiple of that of channel A the signals between the two channels cannot always reach the phase synchronization So to keep the harmonic relation between the signals of two channels set the frequency of channel A first and then set harmonic grade The frequency of channel B can be changed automatically Do not use the frequency of channel B 3 3 2 Setting of phase shift of channel B If the harmonic wave of channel B has been set press the key of Phase to select Phase of channel B Now the signals of two channels are completely synchronous with the phase difference of 0 The phase differenc
39. w a series of increasing by distant or decreasing by distant frequencies with the step of 12 5kHz are obtained in fast and accurate way The Step entering method can only be used in the frequency of channel A or the amplitude of channel A 3 1 3 Knob adjusting In practice signal needs to be adjusted sequentially sometimes so number adjusting knob will be used There is a blink position of cursor in the numeric display Press the key of lt or gt J to move the blink cursor leftwards or rightwards Rotate the knob on the panel can adjust the number sequentially with increasing 1 by turning it clockwise or decreasing 1 by turning it anticlockwise even carry or barrow from high order digit By the knob data come into effect after entering and do not need enter unit key When the blink cursor moves leftwards the data can be adjusted crudely and when it moves rightwards the data can be adjusted finely 3 1 4 Selecting of input way For known data it is the most convenient to use numeric keys as it can be gotten easily without the generating of transient data no matter how big the change of the data is which is so important For the modifying of the entered data or for entering sequence data it will be more convenient to use the knob But for a series of equidistant data using step key will be much more convenient So user should select neatly according to the different applications 22 User s Manual DDS Function Generator
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