Manual HS4D - Egmont Instruments
Contents
1. It is therefore possible to connect one side of the input to one point in the circuit and the other side of the input to the other point in the circuit and measure the voltage difference directly Advantages of a differential input e No risk of creating a short circuit to ground e Only one channel is required to measure the signal e More accurate measurements since only one channel intro duces a measurement error e The CMRR of a differential input is high If both points have a relative high voltage but the voltage difference between the two points is small the voltage difference can be measured in a low input range resulting in a high resolution 3 1 1 Differential attenuators To increase the input range of the Handyscope HS4 DIFF it comes with a differential 1 10 attenuator for each channel This differen Introduction tial attenuator is specially designed to be used with the Handyscope HS4 DIFF Figure 3 3 Differential attenuator For a differential input both sides of the input need to be at tenuated La Figure 3 4 Differential input Standard oscilloscope probes and attenuators only attenuate one side of the signal path These are not suitable to be used with a differential input Using these on a differential input will have a negative effect on the CMRR and will introduce measurement errors Figure 3 5 Differential input d i 2 3 2 The Differential Attenuator and the inputs of the Ha2. Figure 7 3 USB power cable One end of this cable can be connected to a second USB port on the computer the other end can be plugged in the external power input at the rear of the instrument The power for the instrument will be taken from two USB ports of the computer A The outside of the external power connector is connected to 5 V In order to avoid shortage first connect the cable to the Handyscope HS4 DIFF and then to the USB port Chapter 7 A 1 2 7 3 Power adapter In case a second USB port is not available or the computer still can t provide enough power for the instrument an external power adapter can be used When using an external power adapter make sure that e the polarity is set correctly e the voltage is set to a valid value for the instrument and higher than the USB voltage e the adapter can supply enough current preferably gt 1 A e the plug has the correct dimensions for the external power input of the instrument USB The Handyscope HS4 DIFF is equipped with a USB 2 0 High speed 480 Mbit s interface with a fixed cable with type A plug It will also work on a computer with a USB 1 1 interface but will then operate at 12 Mbit s Extension Connector nS e JJ gt o gt gt gt JD Y J Y Figure 7 4 Extension connector To connect to the Handyscope HS4 DIFF a 25 pin female D sub connector is available containing the following signals 32 Pin Description
3. 97 65 pV Signal coupling The Handyscope HS4 DIFF has two different settings for the signal coupling AC and DC In the setting DC the signal is directly Introduction coupled to the input circuit All signal components available in the input signal will arrive at the input circuit and will be measured In the setting AC a capacitor will be placed between the input connector and the input circuit This capacitor will block all DC components of the input signal and let all AC components pass through This can be used to remove a large DC component of the input signal to be able to measure a small AC component at high resolution A When measuring DC signals make sure to set the signal coupling of the input to DC 14 Chapter 3 O 4 1 4 2 4 3 Driver installation Before connecting the Handyscope HS4 DIFF to the com puter the drivers need to be installed Introduction To operate a Handyscope HS4 DIFF a driver is required to inter face between the measurement software and the instrument This driver takes care of the low level communication between the com puter and the instrument through USB When the driver is not installed or an old no longer compatible version of the driver is installed the software will not be able to operate the Handyscope HS4 DIFF properly or even detect it at all The installation of the USB driver is done in a few steps Firstly the driver has to be pre installed by the drive
4. Ee DE S 29 7 1 1 USB power cable 30 112 Poweradabter 24 46 5548 EE aed wi 31 72 USB ociosa ee eee AERA DA Dae ae 31 7 3 Extension Connector o karua 31 8 Specifications 33 Contents 8 1 Acquisition system 33 82 BNC inputs CHI to CHA pedt bea Ms Rg ME 33 8 3 Trigger system 2 6s ee Ree Ee WA ER N N 34 OA a a ae eG od BEER RE te BEE ie N 34 SO POWER is EE ee BOE N N SEE 34 80 Physical soso WERE e ie Re ER DoE Sy 34 87 IO connectors cisco dug daa ero da hd 34 8 8 System requirements 42 35 8 9 Environmental conditions 35 8 10 Certifications and Compliances 35 S 1L Package GOM EntS iker rss 35 Safety When working with electricity no instrument can guaran tee complete safety It is the responsibility of the person who works with the instrument to operate it in a safe way Maximum security is achieved by selecting the proper in struments and following safe working procedures Safe working tips are given below Always work according local regulations Work on installations with voltages higher than 25 Vac or 60 Vpc should only be performed by qualified personnel Avoid working alone e Observe all indications on the Handyscope HS4 DIFF before connecting any wiring Check the probes test leads for damages Do not use them if they are damaged Take care when measuring at voltages higher than 25 Vac or 60 Vpc Do not operate
5. Pin Description 1 Ground 14 Ground 2 Reserved 15 Ground 3 External Power in DC 16 Reserved 4 Ground 17 Ground 5 5V out 10 mA max 18 Reserved 6 Ext sampling clock in TTL 19 Reserved 7 Ground 20 Reserved 8 Ext trigger in TTL 21 Reserved 9 Data OK out TTL 22 Ground 10 Ground 23 PC SDA 11 Trigger out TTL 24 I C SCL 12 Reserved 25 Ground 13 Ext sampling clock out TTL Table 7 2 Pin description Extension connector All TTL signals are 3 3 V TTL signals which are 5 V tolerant so they can be connected to 5 V TTL systems Pins 9 11 12 13 are open collector outputs Connect a pull up resistor of 1 kOhm to pin 5 when using one of these signals Chapter 7 8 1 8 2 Specifications Acquisition system Number of input channels 4 analog CH1 CH2 CH3 CH4 isolated BNC Maximum sampling rate depending on model 12 bit 50 MS s 25 MS s 10 MS s or 5 MS s 14 bit 3 125 MS s 16 bit 195 kS s Maximum streaming rate depending on model 12 bit 500 kS s 250 kS s 100 kS s or 50 kS s 14 bit 480 kS s 250 kS s 99 kS s or 50 kS s 16 bit 195 kS s 195 kS s 97 kS s or 48 kS s Sampling source internal quartz external Internal Quartz Accuracy 0 01 Stability 100 ppm over 40 C to 85 C External On extension connector Voltage 3 3 V TTL 5 V TTL tolerant Frequency range 95
6. Please ignore the warning and continue installation Cancel Figure 4 5 Driver install step 4 The driver install utility now has enough information and can install the drivers Clicking Install will remove existing drivers and install the new driver A remove entry for the new driver is added to the software applet in the Windows control panel Chapter 4 E y Setup TiePie engineering instrument driver al al Ready to Install Setup is now ready to begin installing TiePie engineering instrument driver on your computer Click Install to continue with the installation or click Back if you want to review or change any settings Destination location C Program Files TiePie TiePie instrument driver lt Back Cancel Figure 4 6 Driver install step 5 As mentioned Windows XP SP2 and newer may warn for the USB drivers not being Windows Logo tested Please ignore this warning and continue anyway Software Installation A The software you are installing has not passed Windows Lago testing to verify its compatibility with Windows lt P Tell me why Continuing your installation of this software may impair or destabilize the correct operation of your system either immediately or in the future Microsoft strongly recommends that you stop this installation now and contact the software vendor for software that has passed Windows Logo testin
7. the equipment in an explosive atmosphere or in the presence of flammable gases or fumes Do not use the equipment if it does not operate properly Have the equipment inspected by qualified service personal If necessary return the equipment to TiePie engineering for service and repair to ensure that safety features are main tained Safety Declaration of conformity J TiePie TiePie engineering Koperslagersstraat 37 8601 WL Sneek The Netherlands engineering EC Declaration of conformity We declare on our own responsibility that the product Handyscope HS4 DIFF 5MHz Handyscope HS4 DIFF 10MHz Handyscope HS4 DIFF 25MHz Handyscope HS4 DIFF 50MHz for which this declaration is valid is in compliance with EN 55011 2009 A1 2010 IEC 61000 6 1 EN 61000 6 1 2007 EN 55022 2006 A1 2007 IEC 61000 6 1 EN 61000 6 1 2007 according the conditions of the EMC standard 2004 108 EC and also with Canada ICES 001 2004 Australia New Zealand AS NZS Sneek 1 11 2010 ir A P W M Poelsma Declaration of conformity Environmental considerations This section provides information about the environmental impact of the Handyscope HS4 DIFF Handyscope HS4 DIFF end of life handling Production of the Handyscope HS4 DIFF required the extraction and use of natural resources The equipment may contain sub stances that could be harmful to the environment or human health if improperly handled at the Handyscope HS4 DIFF
8. 16 bits are available too with reduced maximum sampling frequency resolution Model 50 Model 25 Model 10 Model 5 12 bit 50 MS s 25 MS s 10 MS s 5 MS s 14 bit 3 125 MS s 3 125 MS s 3 125 MS s 3 125 MS s 16 bit 195 kS s 195 kS s 195 kS s 195 kS s The Handyscope HS4 DIFF supports high speed continuous Table 3 1 Maximum sampling freguencies streaming measurements The maximum streaming rates are resolution Model 50 Model 25 Model 10 Model 5 12 bit 500 kS s 250 kS s 100 kS s 50 kS s 14 bit 480 kS s 250 kS s 99 kS s 50 kS s 16 bit 195 kS s 195 kS s 97 kS s 48 kS s Table 3 2 Maximum streaming rates Introduction With the accompanying software the Handyscope HS4 DIFF can be used as an oscilloscope a spectrum analyzer a true RMS voltmeter or a transient recorder All instruments measure by sam pling the input signals digitizing the values process them save them and display them 3 1 Differential input Most oscilloscopes are equipped with standard single ended inputs which are referenced to ground This means that one side of the input is always connected to ground and the other side to the point of interest in the circuit under test Figure 3 1 Single ended input Therefore the voltage that is measured with an oscilloscope with standard single ended inputs is always measured between that specific point and ground When the voltage is not referenced to ground
9. 8601 WL SNEEK The Netherlands The Netherlands Tel 31 515 415 416 Fax 31 515 418 819 E mail support tiepie nl Site www tiepie nl
10. Handyscope HS4 DIFF User manual TiePie engineering engineering ATTENTION Measuring directly on the line voltage can be very dangerous Copyright 2014 TiePie engineering All rights reserved Revision 2 9 October 2014 Despite the care taken for the compilation of this user manual TiePie engineering can not be held responsible for any damage resulting from errors that may appear in this manual Contents 1 Safety 1 2 Declaration of conformity 3 3 Introduction 5 3 1 Differential input o s 2 632 64 be pew WER Eg 6 3 1 1 Differential attenuators 7 3 1 2 Differential test lead 9 32 DAMPE oa os Sag OR ONE A aS 9 3 3 Sample frequency o 10 33 1 ANSSING ieee eben ea See be dads 11 d4 Digitizing 2 4 4 4 046 8 PW bd ba dae es 13 3 0 Signal Coupling ya ie bose gd a be RM ie BY 13 4 Driver installation 15 AL Introduction co oros rad 15 4 2 Where to find the driver setup 15 4 3 Executing the installation utility 15 5 Hardware installation 21 5 1 Power the instrument 21 SLL External power soi oras sa 21 5 2 Connect the instrument to the computer 22 5 2 1 Found New Hardware Wizard 23 5 3 Plug into a different USB port 25 6 Front panel 27 6 1 Channel input connectors 27 6 2 Power indicator e om e RR ER a eh ees 27 7 Rear panel 29 Ll BEWEER oa de a e N ie
11. MHz to 105 MHz Memory 128 kSamples per channel BNC inputs CH1 to CH4 Type Differential Resolution 12 14 16 bit user selectable Accuracy 0 3 of full scale 1 LSB Range 200 mV to 80 V full scale Coupling AC DC Impedance 1 MQ 30 pF Maximum voltage 200 V DC AC peak lt 10 kHz Maximum voltage with 1 10 attenuator500 V DC AC peak lt 10 kHz Maximum common mode voltage 200 mV to 800 mV ranges 2 V 2 V to 8 V ranges 20 V 20 V to 80 V ranges 200 V Common Mode Rejection Ratio 48 dB Channel Isolation 500 V Channel Separation 80 dB Bandwidth 3dB 50 MHz AC coupling cut off frequency 3dB 1 5 Hz Specifications 8 3 8 4 8 5 8 6 8 7 Trigger system System digital 2 levels Source CH1 CH2 CH3 CH4 digital external AND OR Trigger modes rising slope falling slope inside window outside window Level adjustment 0 to 100 of full scale Hysteresis adjustment 0 to 100 of full scale Resolution 0 024 12 bits Pre trigger 0 to 128 ksamples 0 to 100 one sample resolution Post trigger 0 to 128 ksamples 0 to 100 one sample resolution Digital external trigger Input extension connector Range 0 to 5 V TTL Coupling DC Interface Interface USB 2 0 High Speed 480 Mbit s USB 1 1 Full S
12. all utility will re move them before installing the new driver To remove the old driver successfully it is essential that the Handyscope HS4 DIFF is disconnected from the computer prior to starting the driver in stall utility When the Handyscope HS4 DIFF is used with an external power supply this must be disconnected too Chapter 4 je setup TiePie engineering instrument driver E El E Information Please read the following important information before continuing Before installing the new drivers existing old drivers will be uninstalled from the computer Therefore make sure that all TiePie engineering instrument devices are disconnected from the computer When any instrument is used with an external power supply make sure that the external power supply is disconnected from the instrument as well lt Back Cancel Figure 4 2 Driver install step 2 When the instrument is still connected the driver install utility will recognize it and report this You will be asked to continue anyway Setup z ES p There still appears to be a TiePie instrument connected to the system Make sure to disconnect it Continue anyway Figure 4 3 Driver install Instrument is still connected Clicking No will bring back the previous screen The instru ment should now be disconnected Then the removal of the existing driver can be continued by c
13. atically and click Nezxt Found New Hardware Wizard Please wait while the wizard installs the software GT ag TiePie instrument a TiePie sys To CAWINDOWSKSvstem32ADRIVERS lt Back Nest gt Cancel Figure 5 3 Hardware install step 3 The New Hardware wizard will now copy the required files to their destination 24 Chapter 5 9 9 F 7 Found New Hardware Wizard Completing the Found New Hardware Wizard The wizard has finished installing the software for mm TiePie instrument a Click Finish to close the wizard Cancel Figure 5 4 Hardware install step 4 The first part of the new driver is now installed Click Finish to close the wizard and start installation of the second part which follows identical steps Once the second part of the driver is installed measurement software can be installed and the Handyscope HS4 DIFF can be used Plug into a different USB port When the Handyscope HS4 DIFF is plugged into a different USB port some Windows versions will treat the Handyscope HS4 DIFF as different hardware and will ask to install the drivers again This is controlled by Microsoft Windows and is not caused by TiePie engineering Hardware installation Chapter 5 6 1 6 2 Front panel O OP O EP Figure 6 1 Front panel Channel input connectors The CH1 CH4 BNC connectors are the main inputs of the acq
14. ation of the second part will start automatically Installation of the second part is identical to the first part therefore they are not described individ ually here Chapter 5 5 2 1 Found New Hardware Wizard Found New Hardware Wizard Welcome to the Found New Hardware Wizard S Windows will search for current and updated software by looking on your computer on the hardware installation CD or on the Windows Update Web site with your permission Read our privacy policy Can Windows connect to Windows Update to search for software Yes this time only Yes now and every time connect a device Click Next to continue Figure 5 1 Hardware install step 1 This window will only be shown in Windows XP SP2 or newer No drivers for the Handyscope HS4 DIFF can be found on the Windows Update Web site so select No not this time and click Nezxt Hardware installation Found New Hardware Wizard This wizard helps vou install software for TiePie instrument E 9 If your hardware came with an installation CD E or floppy disk insert it now What do you want the wizard to do Install from a list or specific location Advanced Click Next to continue Figure 5 2 Hardware install step 2 Since the drivers are already pre installed on the computer Windows will be able to find them automatically Select Install the software autom
15. connecting a standard single ended oscilloscope input to the two points would create a short circuit between one of the points and ground possi bly damaging the circuit and the oscilloscope A safe way would be to measure the voltage at one of the two points in reference to ground and at the other point in reference to ground and then calculate the voltage difference between the two points On most oscilloscopes this can be done by connecting one of the channels to one point and another channel to the other point and then use the math function CH1 CH2 in the oscilloscope to display the actual voltage difference There are some disadvantages to this method e a short circuit to ground can be created when an input is wrongly connected e to measure one signal two channels are occupied ET Chapter 3 e by using two channels the measurement error is increased the errors made on each channel will be combined resulting in a larger total measurement error e The Common Mode Rejection Ratio CMRR of this method is relatively low If both points have a relative high voltage but the voltage difference between the two points is small the voltage difference can only be measured in a high input range resulting in a low resolution A much better way is to use an oscilloscope with a differential input Figure 3 2 Differential input A differential input is not referenced to ground but both sides of the input are floating
16. e red dotted signal bottom is the result of the reconstruction The period time of this triangular signal appears to be 4 ms which corresponds to an apparent frequency alias of 250 Hz 1 25 kHz 1 kHz To avoid aliasing always start measuring at the highest sam pling frequency and lower the sampling frequency if required Chapter 3 3 4 3 5 Digitizing When digitizing the samples the voltage at each sample time is converted to a number This is done by comparing the voltage with a number of levels The resulting number is the number cor responding to the level that is closest to the voltage The number of levels is determined by the resolution according to the following relation LevelCount 2Reselution The higher the resolution the more levels are available and the more accurate the input signal can be reconstructed In figure 3 10 the same signal is digitized using two different amounts of levels 16 4 bit and 64 6 bit Figure 3 10 The effect of the resolution The Handyscope HS4 DIFF measures at e g 12 bit resolution 2 2 4096 levels The smallest detectable voltage step depends on the input range This voltage can be calculated as VoltageStep Full InputRange LevelCount For example the 200 mV range ranges from 200 mV to 200 mV therefore the full range is 400 mV This results in a smallest detectable voltage step of 0 400V 4096
17. g 3 STOP Installation Figure 4 7 Driver install Ignore warning and continue Driver installation 19 Chapter 4 is Setup TiePie engineering instrument driver lal Bes Completing the TiePie engineering instrument driver Setup Wizard Setup has finished installing TiePie engineering instrument driver on your computer Click Finish to exit Setup Figure 4 8 Driver install Finished o 5 1 5 1 1 Hardware installation Drivers have to be installed before the Handyscope HS4 DIFF is connected to the computer for the first time See chapter 4 for more information Power the instrument The Handyscope HS4 DIFF is powered by the USB no external power supply is required Only connect the Handyscope HS4 DIFF to a bus powered USB port otherwise it may not get enough power to operate properly External power In certain cases it can be that the Handyscope HS4 DIFF cannot get enough power from the USB port When a Handyscope HS4 DIFF is connected to a USB port the hardware will be powered resulting in an inrush current which is higher than the nominal current After the inrush current the current will stabilize at the nominal current USB ports have a maximum limit for both the inrush current peak and the nominal current When either of them is exceeded the USB port will be switched off As a result the connection to the Handyscope HS4 DIFF
18. licking Nest Clicking Yes will ignore the fact that the instrument is still connected and continue removal of the old driver This option is not recommended as removal may fail after which installation of the new driver may fail as well When no existing driver was found or the existing driver is removed the location for the pre installation of the new driver can be selected Driver installation 18 Setup TiePie engineering instrument driver EE a El Select Destination Location where should TiePie engineering instrument driver be installed O Setup will install TiePie engineering instrument driver into the following folder To continue click Next If vou would like to select a different folder click Browse C Program Files TiePie T iePie instrument driver Atleast 1 1 MB of free disk space is required lt Back Next gt Cancel Figure 4 4 Driver install step 3 On Windows XP and newer the installation may inform about the drivers not being Windows Logo Tested The driver is not causing any danger for your system and can be safely installed Please ignore this warning and continue the installation y Setup TiePie engineering instrument driver ta El Information Please read the following important information before continuing On Windows lt P and newer the installation may inform about the drivers not being Windows Logo tested
19. ndy scope HS4 Diff are differential which means that the outside of the BNC s are not grounded but carry life signals When using the attenuator the following points have to be taken into consideration e do not connect other cables to the attenuator than the ones that are supplied with the instrument e do not touch the metal parts of the BNC s when the atten uator is connected to the circuit under test they can carry a dangerous voltage It will also influence the measurements and create measurement errors e do not connect the outside of the two BNC s of the attenuator to each other as this will short circuit a part of the internal circuit and will create measurement errors e do not connect the outside of the BNC s of two or more at tenuators that are connected to different channels of the Han dyscope HS4 Diff to each other e do not apply excessive mechanical force to the attenuator in any direction e g pulling the cable using the attenuator as handle to carry the Handyscope HS4 DIFF etc Differential test lead The Handyscope HS4 DIFF comes with a special differential test lead This test lead is specially designed to ensure a good CMRR The special heat resistant differential test lead provided with the Handyscope HS4 DIFF is designed to be immune for noise from the surrounding environment Sampling When sampling the input signal samples are taken at fixed inter vals At these intervals the size of the inpu
20. peed 12 Mbit s compatible Power Input from USB or external input Consumption 500 mA max Physical Instrument height 25 mm 1 0 Instrument length 170 mm 6 7 Instrument width 140 mm 5 2 Weight 480 gram 17 ounce USB cord length 1 8 m 70 I O connectors CH1 CH4 BNC Power 3 5 mm power socket Extension connector D sub 25 pins female USB Fixed cable with type A plug 34 Chapter 8 8 8 System requirements PC I O connection USB 2 0 High Speed 480 Mbit s USB 1 1 Full Speed 12 Mbit s compatible Operating System Windows 98 ME 2000 XP Vista 7 8 9 Environmental conditions Operating Ambient temperature 0 C to 55 C Relative humidity 10 to 90 non condensing Storage Ambient temperature 20 C to 70 C Relative humidity 5 to 95 non condensing 8 10 Certifications and Compliances CE mark compliance Yes RoHS Yes 8 11 Package contents Instrument Handyscope HS4 DIFF Test lead 4 x low noise differential with 4 mm banana jacks Accessories 4 x 1 10 differential attenuators USB power cable Software Windows 98 2000 ME XP Vista 7 Drivers Windows 98 2000 ME XP Vista 7 Manual Instrument manual and software user s manual Specifications Chapter 8 If you have any suggestions and or remarks regarding this manual please contact TiePie engineering TiePie engineering P O Box 290 Koperslagersstraaat 37 8600 AG SNEEK
21. r setup program This makes sure that all required files are located where Windows can find them When the instrument is plugged in Windows will detect new hardware and install the required drivers Where to find the driver setup The driver setup program and measurement software can be found in the download section on TiePie engineering s website and on the CD ROM that came with the instrument It is recommended to install the latest version of the software and USB driver from the website This will guarantee the latest features are included Executing the installation utility To start the driver installation execute the downloaded driver setup program or the one on the CD ROM that came with the instrument The driver install utility can be used for a first time Driver installation installation of a driver on a system and also to update an existing driver The screen shots in this description may differ from the ones displayed on your computer depending on the Windows version is Setup TiePie engineering instrument driver ka a Welcome to the TiePie engineering instrument driver Setup Wizard This will install TiePie engineering instrument driver 6 0 0 0 on your computer It is recommended that you close all other applications before continuing Click Next to continue or Cancel to exit Setup E Cancel Figure 4 1 Driver install step 1 When drivers were already installed the inst
22. s end of life In order to avoid release of such substances into the environment and to reduce the use of natural resources recycle the Handyscope HS4 DIFF in an appropriate system that will ensure that most of the materials are reused or recycled appropriately The symbol shown below indicates that the Handyscope HS4 DIFF complies with the European Union s requirements according to Directive 2002 96 EC on waste electrical and electronic equip ment WEEE EE Restriction of Hazardous Substances The Handyscope HS4 DIFF has been classified as Monitoring and Control eguipment and is outside the scope of the 2002 95 EC RoHS Directive Introduction Before using the Handyscope HS4 DIFF first read chapter 1 about safety Many technicians investigate electrical signals Though the measurement may not be electrical the physical variable is of ten converted to an electrical signal with a special transducer Common transducers are accelerometers pressure probes current clamps and temperature probes The advantages of converting the physical parameters to electrical signals are large since many in struments for examining electrical signals are available The Handyscope HS4 DIFF is a portable four channel measur ing instrument with differential inputs The Handyscope HS4 DIFF is available in several models with different maximum sampling fre quencies The native resolution is 12 bits but user selectable reso lutions of 14 and
23. t signal is converted to a number The accuracy of this number depends on the resolution of the instrument The higher the resolution the smaller the voltage steps in which the input range of the instrument is divided The acquired numbers can be used for various purposes e g to create a graph Introduction EA Figure 3 6 Sampling The sine wave in figure 3 6 is sampled at the dot positions By connecting the adjacent samples the original signal can be recon structed from the samples You can see the result in figure 3 7 Figure 3 7 connecting the samples 3 3 Sample frequency The rate at which the samples are taken is called the sampling frequency the number of samples per second A higher sampling frequency corresponds to a shorter interval between the samples As is visible in figure 3 8 with a higher sampling frequency the original signal can be reconstructed much better from the measured samples Chapter 3 3 3 1 Figure 3 8 The effect of the sampling frequency The sampling frequency must be higher than 2 times the high est frequency in the input signal This is called the Nyquist fre quency Theoretically it is possible to reconstruct the input signal with more than 2 samples per period In practice 10 to 20 sam ples per period are recommended to be able to examine the signal thoroughly Aliasing When sampling an analog signal with a certain sampling frequency signals appear in the output
24. ui sition system The isolated BNC connectors are not connected to the ground of the Handyscope HS4 DIFF Power indicator A power indicator is situated at the top cover of the instrument It is lit when the Handyscope HS4 DIFF is powered Chapter 6 Td Rear panel Figure 7 1 Rear panel Power The Handyscope HS4 DIFF is powered through the USB If the USB cannot deliver enough power it is possible to power the in strument externally The Handyscope HS4 DIFF has two external power inputs located at the rear of the instrument the dedicated power input and a pin of the extension connector The specifications of the dedicated power connector are Pin Dimension Description Center pin 1 3 mm ground Outside bushing 03 5 mm positive Figure 7 2 Power connector Besides the external power input it is also possible to power the instrument through the extension connector the 25 pin D sub connector at the rear of the instrument The power has to be applied to pin 3 of the extension connector Pin 4 can be used as ground The following minimum and maximum voltages apply to both power inputs Rear panel 29 Minimum Maximum 4 5 Vpa 14 VDc Table 7 1 Maximum voltages Note that the externally applied voltage should be higher than the USB voltage to relieve the USB port 7 1 1 USB power cable The Handyscope HS4 DIFF is delivered with a special USB exter nal power cable
25. will be lost Most USB ports can supply enough current for the Handyscope HS4 DIFF to work without an external power supply but this is not always the case Some battery operated portable computers or bus powered USB hubs do not supply enough current The exact value at which the power is switched off varies per USB controller so it is possible that the Handyscope HS4 DIFF functions properly on one computer but does not on another In order to power the Handyscope HS4 DIFF externally an external power input is provided for It is located at the rear of the Hardware installation 5 2 22 Handyscope HS4 DIFF Refer to paragraph 7 1 for specifications of the external power intput Connect the instrument to the computer After the new driver has been pre installed see chapter 4 the Handyscope HS4 DIFF can be connected to the computer When the Handyscope HS4 DIFF is connected to a USB port of the com puter Windows will report new hardware The Found New Hard ware Wizard will appear Depending on the Windows version the New Hardware Wizard will show a number of screens in which it will ask for information regarding the drivers of the newly found hardware The appear ance of the dialogs will differ for each Windows version and might be different on the computer where the Handyscope HS4 DIFF is installed The driver consists of two parts which are installed sepa rately Once the first part is installed the install
26. with frequencies equal to the sum and difference of the signal frequency and multiples of the sampling frequency For example when the sampling frequency is 1000 Hz and the signal frequency is 1250 Hz the following signal frequencies will be present in the output data Multiple of sampling frequency 1250 Hz signal 1250 Hz signal 1000 1000 1250 250 1000 1250 2250 0 0 1250 1250 0 1250 1250 1000 1000 1250 2250 1000 1250 250 2000 2000 1250 3250 2000 1250 750 Table 3 3 Aliasing As stated before when sampling a signal only frequencies lower than half the sampling frequency can be reconstructed In this case the sampling frequency is 1000 Hz so we can we only observe Introduction A 12 signals with a frequency ranging from 0 to 500 Hz This means that from the resulting frequencies in the table we can only see the 250 Hz signal in the sampled data This signal is called an alias of the original signal If the sampling frequency is lower than twice the frequency of the input signal aliasing will occur The following illustration shows what happens Tapparent 4 ms Figure 3 9 Aliasing In figure 3 9 the green input signal top is a triangular signal with a frequency of 1 25 kHz The signal is sampled with a fre quency of 1 kHz The corresponding sampling interval is 1 1000Hz lms The positions at which the signal is sampled are depicted with the blue dots Th
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