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Appendix A Specifications and Quick Starts

1. A 1 5 of display 1 ls digit 20 A 2 5 of display 5 ls digits Resistance 200 Q 1 0 of display 3 ls digits 2 KQ 20 KQ 200 kQ 2 MQ 1 0 of display 1 ls digit 20 MQ 1 5 of display 2 ls digits 2000 MQ 5 5 of display 5 ls digits AC Voltage 200 mV 2 20 200 1000 V 1 2 of display 3 ls digits 750 V 1 5 of display 3 ls digits AC Current 200 pA 2 mA 1 5 of display 3 ls digits 20 mA 200 mA 2 3 of display 5 ls digits 20 A 3 5 of display 7 ls digits Frequency 2 kHz 20 kHz 2 5 of display 3 ls digits Capacitance 200 pF 200 nF 2 5 of display 3 ls digits 20 uF 200 uF Example Problem AA 1 Calculating Uncertainty in a Measurement with an RS DMM An RS DMM on its 2V range displays 0 123 volt Write this measurement in standard form Solution The accuracy Table AA 4 is specified as 0 8 of the display reading 1 Is digit This translates to 0 123 x 0 008 0 000984 0 001 1 Is digit in the display 4 5 of display 5 ls digits 0 001984 before rounding 0 002 volt rounded to 1 significant digit Thus the measurement written in standard form is 0 123 0 002 volt The precision of the measurement and the precision of the uncertainty must both extend to the same decimal place in this case the third NOTE For other measurements on other ranges the precision may extend to a decimal place other than the third AA 7 Specifications and Qu
2. CH2 Menu button once or twice to remove the CH2 trace from the display Press MEASURE to go back to the MEASURE state then press AUTOSET Attenuation In order for the numerical results in display boxes to be correct you must remove any attenuation that may have been inadvertently set on the CH1 input by other users To do this do the following While in MEASURE state press the CH1 Menu button Press the bottom toggle button as many times as it takes to bring up X1 in the Probe box Press the MEASURE button then press AUTOSET At this stage the sinewave should fill the waveform area of the screen as is shown in Figure AA 16 Digital J aggies As a first time user of a digital oscilloscope you will no doubt notice the jagged appearance of the sine wave This is normal and results from the process of digitization In any run the input signal is sampled 2500 times making 2500 line segments in the display AA 18 Figure AA 16 A typical display on the Tek TDS210 DSO At this stage your oscilloscope need only resemble what is shown here The Display Screen Identify the following aspects of your display screen The Icon Display The icon in the upper left hand corner shows the pres ent acquisition mode Icons for the various modes are reproduced below Sample Mode is the default mode and the current reading should be Sample Mode Wile Sample mode ef le Peak detect mode JT L Average mode Trigger Status
3. Figure AA 6 Tree structure of the menus To give the flavor of what is involved in examining and changing a mode we shall have you confirm the GPIB and RS 232 values in preparation for Lab 3 Do the following With the instrument ON turn the menu ON by pressing the Shift button then the gt button Keep pressing the gt button until you reach E I O MENU Press the v button once to move down one level of the menu to 1 GPIB ADDR Press the v button again to move down one level to ADDR is the current GPIB address of the instrument Press to go back to 1 GPIB ADDR Press gt to go to 2 Interface Press v to go to RS 232 then press gt to go to GPIB When you have finished press the Auto Man ENTER button The instrument should beep and show SAVED in the display to indicate that the change has been saved For the Programmer Communication The instrument supports RS 232 and GPIB communi cation though only one interface may be used at a time and that interface must be selected from the front panel The connectors are located on the rear panel GPIB is the default interface Parameter values are GPIB Address 22 default RS 232 Baud Rate 9600 default Coding 7 bit ASCII default Parity Even Stop Bits 2 Handshaking DTR DSR The instrument provides error checking of remo
4. If your signal is triggered it is frozen in position and not moving to the right or left Trigger status upper middle top of the screen shows if the trigger source is adequate or if acquisition is stopped Current reading should be Trig d meaning the signal is triggered Horizontal Trigger Position The downward arrow marker upper middle of the screen shows the horizontal trigger position This is the position on the waveform at which the acquisition begins This also shows the horizontal position since the horizontal position control Figure AA 17 moves the trigger position horizontally For your own interest rotate the Horizontal Position control back and forth now to see its effect on the marker Then reset the marker to its original center position HORIZONTAL lt Position gt HORIZONTAL MENU SEC DIV Yo 5s 5ns Figure AA 17 The horizontal controls on the oscilloscope Timebase The timebase refers to the time equivalent of 1 horiz ontal cm division on the display A numerical read out shows the main timebase setting Current reading should be 1 ms Vertical Scale Factors Numerical readouts bottom left show the vertical scale factors for CH1 and CH2 A vertical scale factor refers to the voltage equivalent of each vertical cm division on the display Current readings should be whatever is shown in your version of Figure AA 16 here 2 00 V Ground Reference An on screen marker mi
5. Protection key 4 Display Limit key 5 Voltage Current Adjust Selection key 6 Stored State Recall Reset Menu 7 State Storage Menu Local key 8 View Menu Calibrate key 9 I O Configuration menu Secure key 10 Output On Off key 11 Resolution Selection keys 12 Knob AA 21 Specifications and Quick Starts Specifications A selection of specifications is listed in Table AA 10 The supply can be controlled remotely as well as from the front panel It is of interest that the resolution available remotely exceeds the resolution available via the front panel Table AA 10 Some Specifications applying to the tempera ture range 0 to 40 C with the instrument connected to a resistive load Programming Accuracy Voltage lt 0 05 10 mV Current lt 0 2 10 mA Voltage lt 0 05 5 mV Current lt 0 15 5 mA Voltage lt 5 mV Current lt 1 mA Voltage 10 mV Current 1 mA Ripple and Noise lt 0 5 mV rms Settling Time lt 90 msec for the output voltage to change from 1 to 99 following receipt of VOLTage or APPLy com mand via GPIB or RS 232 Readback Accuracy Programming Resolution Front Panel Resolution Quick Start This Quick Start will take you through a test of the instrument s voltage and current outputs Voltage Output Checkout You can confirm the power supply s voltage function by the following procedure Ensure the power supply is OFF Ensure that any load that may have been left c
6. analog input ground AIGND The differ ential amplifier input is also tied to analog ground AA 26 With this configuration the PCI 1200 can monitor 8 different analog input channels via multiplexing In this mode the signal return path is analog ground at the connector through the AISENSE AIGND pin Figure AA 23 Floating Signal In mentation plifier AIGND stru Source 1 ACHO Am 9 Vm AISENSE o Figure AA 23 How to use the RSE input mode to measure the voltage of a source that is floating wrt ground 2 NRSE Input Eight Channels NRSE stands for Non Referenced Single Ended NRSE mode should be used when the source whose voltage is to be measured has one side grounded NRSE means that all input signals are referenced to the same common mode voltage which floats with respect to the PCI 1200 analog ground This common mode volt age is subsequently subtracted by the input instru mentation amplifier In this mode the signal return path is through the terminal of the amplifier at the connector through the AISENSE AIGND pin Figure AA 24 3 Diff Input Four Channels Diff input means that each input signal has its own reference It is the difference between each signal and its reference that is measured The signal and its reference are each assigned an input channel In this mode the PCI 1200 can monitor 4 differential analog input signals via multiplexing The signal return path is throug
7. are printed in UPPERcase optional letters in lowercase A colon separates a command keyword from a lower level keyword Table AA 2 The tree structure of the SOURce command taken from the Agilent E3640A programmable power supply command set The tree of this command has three levels lower branches of the tree are indented for easy identification SOURce CURRent lt current gt MIN IMAX I UP DOWN CURRent MIN IMAX CURRent TRIGgered lt current gt MIN IMAX TRIGgered MIN I MAX Specifications and Quick Starts VOLTage lt voltage gt MIN I MAX IUP DOWN VOLTage MIN MAX VOLTage TRIGgered lt voltage gt MIN I MAX TRIGgered MIN MAX Legend Square brackets indicate optional argu ments curly brackets indicate values or keywords Arrow brackets lt gt indicate an optional numerical value Vertical lines mean or These brackets are not part of the command About the Quick Starts The Quick Starts in the following sections were designed to provide a quick introduction to the instrument It was intended that some of them would be covered in labs or tutorials For maximum effectiveness you are strongly urged to work your way through them before beginning a lab where the instrument is featured The Ohaus Scout Il Electronic Balance General Description In many labs today the mechanical balance has been replaced with an electronic or digital balance The Ohaus Scout II ser
8. be weighed on the pan The balance will initiate a measurement cycle at the end of which a stable reading will appear in the display e For each subsequent object to be weighed press the Zero On button and repeat desired weight unit For the Programmer Communication The Scout II series of balances have a bidirectional RS 232 interface The instrument is able to send measure ments out the serial port and to respond to a small set of commands from a controlling computer The unit is a DCE device it is equipped with a standard DB 9 connector and requires a straight through cable RS 232 Parameters defaults The factory default RS 232 values are Baud Rate 2400 Coding 7 bit ASCII Parity None Stop Bits 2 Handshaking None Other values are possible but the defaults give the most reliable behavior more on this below The beginner is strongly urged to keep to the defaults RS 232 Commands All commands must be in standard ASCII form and terminate with a carriage return lt CR gt r or the carriage return line feed combination lt CR gt lt LF gt r n All strings returned by the balance are ter minated with a carriage return line feed Commands supported are listed in Table AA 3 Table AA 3 RS 232 Command Table for Ohaus Scout II Series of Electronic Balances Some of these functions e g certain units must first be turned on manually via the front panel Command Meanin Print current mod
9. channel 0 DACIOUT is the voltage output signal for analog output channel 1 Pin 11 AGND is the ground reference point for both analog output channels and analog input channels AA 28 The following output ranges are available Bipolar output 5 V Unipolar output 0to10V Maximum load current 2 mA for 12 bit linearity Output coupling DC Output impedance 0 2 Q typ Current drive 2 mA Power on state OV Digital 1 0 The digital I O of a DAQ card is used almost ex clusively in aspects of control A digital input line might be used to monitor the state of a switch whether it is open or closed A digital output line might be used to trigger the state of a switch AC or DC and thereby control a high power device like a heater or motor Pins 13 through 37 of the I O connector are digital I O signal pins Digital I O on the PCI 1200 uses the 82C55A IC The 82C55A is a general purpose peripheral interface containing 24 program mable I O pins These pins represent the three 8 bit ports PA PB and PC of the 82C55A Pins 14 through 21 are connected to the digital lines PA lt 7 0 gt for digital I O port A Pins 22 through 29 are connected to the digital lines PB lt 7 0 gt for digital I O port B Pins 30 through 37 are connected to the digital lines PC lt 7 0 gt for digital I O port C Pin 13 DGND is the digital ground pin for all three digital I O ports Selected Specifications for Digital I 0 24 1 O three 8 bit ports
10. described elsewhere in this appendix the Tek oscilloscope has no provision to be set to GPIB or RS 232 mode exclusively It can in principle be remotely controlled over both interfaces concurrently This is not possible simultaneously RS 232 The values of the RS 232 parameters can be set from the front panel as follows With the oscilloscope ON press the Utility button then press the Options button and finally press the RS232 Setup button Recommended param eters are Baud Rate 9600 Flow Control None EOL String lt CR gt if you are using a Mac lt CR gt lt LF gt if you are using a Windows PC lt LF gt if a UNIX box Parity None If necessary make the changes required GPIB The values of the GPIB parameters can be set as follows With the oscilloscope ON press the Utility button then press the Options button and finally press the GPIB Setup button Values recommended are AA 20 Address 1 Bus Connection Talk Listen If necessary make the changes required Waveform Transfer Waveforms can be transferred from the oscilloscope to the controlling computer and vice versa as explained in Figure AA 14 To put this into words you can transfer the contents of the five memory locations from the oscilloscope to your computer but you can transfer a waveform from your computer to the oscilloscope s REFA and REFB locations only This is a somewhat advanced topic You will likely not be doing t
11. other instruments or for your project General Description and AC current resistance continuity Diode Test The Agilent Model 34401A DMM Figure AA 5 is a DC DC Ratio measurements period and frequency It research grade 6 1 2 digit instrument with an accur will perform a number of MATH operations and can acy in the 0 003 range It is claimed to employ a store up to 512 readings in internal memory This is continuously integrating multislope MI ADC It one of the best instruments of its kind on the market provides measurements of DC and AC voltage DC that is within the budget of a teaching laboratory ka a FUNCTION a y F MAH EN acl ow ll a el el ee Vs S E iy HEWLETT 344014 EES PACKARD LuTMETER E a ea ey Far MATH a acl oo Peried P V RANGE DIGITS ee w Autos Man onon EMU kacai lt PO KJ cJ k Figure AA 5 The front panel of the Agilent Model 34401A digital multimeter at a glance This shows Measurement function keys Math operation keys Single Trigger AutoTrigger Reading Hold key Shift Local key Front Rear Input Terminal Switch Range Number of Digits Displayed keys D Menu Operation keys AA 9 Specificatios and Quick Starts Specifications The instrument can be operated at three precision levels 4 1 2 digits 5 1 2 digits and 6 1 2 digits The precision selected determines the measurement speed the more precision the slower the spee
12. sensors terminate in a DIN 5 Figure AA 20 The pinout looking into the socket on the SBI box For the Programmer Communication The values of the RS 232 parameters are fixed Baud rate 2400 Actual rate 2327 bps Word Length 8 bits Parity none Stop Bits 2 Transmit Data Must transmit all 1 s to power SBI The data consists of 4 byte groups of the form D5 D4 D3 D2 D1 DO D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 DO D11 D10 D9 D8 D7 D6 don t care don t care 0 0 I don t care 1 0 0 Ly 1 don t care A high order bit of 0 means the byte originates from Port 1 if 1 then Port 2 The bytes from any one port are always sent in the low byte high byte order Thus the bytes are in groups of 4 but the order of the bytes read by the controlling computer depends on where in the cycle of 4 reading began Thus the ordering may be 2 bytes from Port 1 2 bytes from Port 2 which Specifications and Quick Starts is the desired order An undesired order would be 1 high byte from Port 1 2 bytes from Port 2 followed by 1 low byte from Port 1 and so forth Thus the bytes need to be tested as to their port of origin One strategy of programming would be to shift bytes not in the desired order Of course this problem would exist in reading from the ID input lines as well as from the Input Voltage lines The Vernier Software SBI box is now regarded by the company as a lega
13. the DMM sends data at the rate of 2S s approximately Data Format The DMM outputs a frame of data of 14 bytes inclusive of an ASCII lt CR gt byte at the end The structure is explained by the following two examples BYTES 123 456789ABCODE Examplel DeC E 99 9T CR Example2 I 999MohmcCR Unlike the Ohaus electronic balance described in the previous section that uses only a portion of its 22 byte frame the RS DMM uses its full frame here 14 bytes What could be called a Mode string occupies bytes 1 3 a numeric string bytes 4 9 and a unit string bytes A D Sample Rate Maximum recommended sample rate rate of pro ducing a voltage transition on its RxD line is 1 S s This does not apply to COM mode in which the sample output is set by the DMM itself at about 2 S s approximately Peculiarities As already stated the RS DMM will not send unless the DTR line is unasserted in software This requires the programmer to pay attention to the platform used LabVIEW has a VI to enable the platform to be identified The student driver RS Open makes this issue transparent to the student For more information see Chapter 5 and in particular Figure 5 21 Specifications and Quick Starts Agilent Model 34401A Digital Multimeter At the time of writing only two of these instruments were available in the Physical Sciences lab for student use You will likely be using this instrument if at all for purposes of calibrating
14. 0 A signal generator Figure AA 10 is a fully digital instrument of late 1990s tech nology Though developed by Telulex Corp it is now marketed by Berkeley Nucleonics Cal under the model name BNC Model 625A signal generator Figure AA 10 Telulex Model SG 100 A otherwise known as the BNC Model 625A signal generator The instrument provides a broad range of operating modes such as arbitrary waveform pulse word data integration function dual tone sweep VCO AM FM SSB FSK and burst An arbitrary waveform can be downloaded to the instrument over the RS 232 interface from a host computer The instrument is claimed to have an architecture based on the latest advances in digital signal processing DSP and direct digital synthesis DDS technology The instrument is claimed to deliver clean fully synthesized DC to 21 5 MHz modulated or unmod ulated waveforms with 0 01 Hz frequency resolution and 1 mV and 0 1 dBm amplitude resolution A large LCD display allows all modulation parameters to be seen simultaneously and to assist in the navigation of the various modes Front Panel As can be seen in the figure the front panel is equipped with a multiline LCD screen a large rotary knob a keypad for entering numbers and selecting AA 14 functions and two BNC connectors lower right hand corner Of the latter the SIG Out connector is the main signal output The SYNC Out connector is a TTL CMOS compatible square wave out
15. Appendix A Specifications and Quick Starts We have gathered here for reference specifications and instructions for the use of the instruments referred to in this course The important functionality of these instruments available via the front panel controls is described along with some of the remote control commands of interest to the programmer You are strongly urged to work through the quickstarts for each instrument before attempting a lab in which the instrument is featured For a listing of student drivers for the instruments if they exist see Chapter 5 Index Instrument Ohaus Scout II Electronic Balance Radio Shack Manual Auto Range Digital Multimeter Agilent Model 34401A Digital Multimeter Instek Model GFG 8016G Signal Generator Telulex Model Sg 100 A Signal Generator Tektronix TDS210 Digital Oscilloscope Agilent Model HPE3640 Programmable Power Supply Vernier Software SBI Box National Instruments PCI 1200 DAQ Card Drivers SCPI Compliant Page Yes No AA 3 Yes No AA 6 Yes Yes AA 9 AA 12 Yes No AA 14 Yes Yes AA 16 Yes Yes AA 21 Yes No AA 24 Yes AA 25 Introduction Manuals The size of manuals that accompany instruments can be large We can reproduce here only a selection of the specifications for each instrument and those that are considered to be of interest to the science student Manuals produced by the manufacturers are available in the physics lab for shortterm borrowing Some manuals ca
16. N OFF Tektronix TDS 220 SR r oue tion on two signals simultaneously applied to the CH1 and CH2 connectors Maximum number of sam ples per channel is 2500 Maximum analog bandwidth is 60 MHz with bandwidth limiting BWL OFF or 20 MHz with BWL ON Its input impedance DC coup led is 1 MQ 2 in parallel with 20 pF 3 pF There are three acquisition modes sample peakdetect and average Accuracy is typically 3 in average acquis ition mode AUTOSET AA 16 om wn CHt CH2 EXT TRIG MOIO Figure AA 12 Line drawing of the Tektronix Model TDS210 digital real time oscilloscope MATH The instrument performs a limited number of math operations for example CH1 CH2 CH2 CH1 CH1 CH2 CH1 Inverted and CH2 Inverted These functions are selected via the MATH Menu button When a function is selected the instrument places the result in memory location MATH enters MATH mode displays the waveform and turns both channels OFF Measurements that would otherwise be possible on the CH1 and CH2 signals are disabled You can exit MATH mode by turning CH1 or CH2 back on via the CH1 or CH2 menu buttons Storage The waveforms applied to the CH1 and CH2 con nectors that are sampled simultaneously are stored in memory locations CH1 and CH2 These wave forms may be subsequently transferred to memory locations REFA and REFB f
17. Rules 1 All ASCII commands are case insensitive meaning that upper and lower case letters are treated equally 2 When the 625 has finished executing a command it will return a command prompt which is the DOS gt character 109 If a long string of commands is sent to the 625 a separate gt character will be returned for each command as it is executed see the Peculiarities section below 3 All whitespace characters lt CR gt s lt LF gt s tabs spaces and commas between commands are ignored Invalid commands ASCII characters that are not listed in the command menu are likewise ignored 4 If the 625 is reporting data to the control program it will place a colon character before the data 5 An ASCII hello string is sent to the RS 232 port on power up It is therefore not recommended that the instrument be turned OFF and then ON again during a communication session otherwise the hello string will enter the serial buffer and will have to be specially purged in software Remote Control Example A programmer accustomed to SCPI compliant instru ments will find the programming of this signal generator to be highly unusual not to say archaic An example of an ASCII character command sequence is the following AA 15 Specifications and Quick Starts MO Fl 3 1412 N 2 32 FO NOTE Spaces are not actually needed between char acters They were added here only to make the com mands more r
18. The instrument supports communication via RS 232 only The values of the RS 232 parameters are Baud Rate 300 1200 2400 4800 9600 19200 38400 57600 115200 default 9600 Coding 8 bit ASCII Parity None Stop Bits 1 Handshaking None The manufacturer recommends the instrument be operated with default settings You are strongly urged to follow this advice Serial Port Wiring The wiring of the serial port is a standard female DB9 The instrument is a DCE and connects to the com Specifications and Quick Starts puter with a straight through cable Instrument Specific Commands The instrument is not SCPI compliant The tradeoff is the instrument s relatively low cost The designers of the instrument s firmware adopted the strategy that each key on the keypad has an associated ASCII character which when sent to the instrument over the RS 232 port has the same effect as pressing that key on the keypad The keypad and the associated ASCII characters can be seen more clearly in Figure AA 11 TU 8 Next Cursor 99 DTMF Gen Function Field T LD 5 Mode Offset DTMF D FSK O gt R 2 Store Recall Remote Pwr Meas FM Q eL 0 Arbitrary Sinewave TTL Cmos Z0 500 Figure AA 11 A line drawing of the front panel of the Telulex Model SG 100 A signal generator Programming
19. bit resolution The National Instruments data acquisition DAQ card costs 700 and samples at a maximum rate of 10 000 per second 10 kS s at 12 bit resolution The greater the sampling speed the finer the detail of a waveform that can be resolved The greater the number of bits word size in the acquisition the greater the precision number of meaningful digits in the measurement A tradeoff exists between sampling speed cost and word size Display and Storage Capability Display capability is related to sample rate and stor age capability Most hand held DMMs of the present generation have a minimum amount of RAM A measurement they make they immediately display on a single line LCD screen A typical DSO on the other hand has a fair amount of memory and can store and display an entire acquisition consisting of perhaps 2500 samples on a multi line LCD screen of as much as 320 pixels wide by 240 pixels high The display and storage capabilities of instrumens are steadily being increased Remote Control Research grade instruments are equipped with one or more communication port most often an RS 232 or GPIB port and increasingly a USB port discussed in Appendix 3 But how controllable an instrument is does vary depending on the instrument s firmware For example the Radio Shack DMM will export a frame of data on its TxD line on command But it supports no remote control of measurement type or range The Agilent 34401A digita
20. cy product It has for some years been superceded by their ULI board and a new product called LabPro which is designed to be used with a USB interface You will not likely be using this box in this course National Instruments PCI 1200 DAQ Card A PCI 1200 digital acquisition DAQ card is installed in all of the computers in the Physical Sciences lab This card is a PCI device and is useable with any computer with a PCI slot The card is complex and so a Quick Start will be directed by the instructor in Lab 4 Why a DAQ Card A DAQ card encapsulates into one system box much of the functionality and control capabilities of a host of stand alone instruments A DAQ card can be used to measure a voltage much like a DMM and to generate an AC signal much like a signal generator A DAQ card can be used to provide control signals for external switches and to monitor the state of external switches And finally a DAQ card can perform these functions more or less simultaneously General Description The PCI 1200 DAQ card pinout shown in Figure AA 21 is manufactured by National Instruments NI the company that markets LabVIEW The card is config ured by the software that NI supplies called DAQ Channel Wizard With this program all card resources can be allocated or just a subset of them The cards in all the computers have been preconfigured for this course The Lines There are 50 lines Reading from the top down there are 8 analog inp
21. d Measure ment speed depends on the function as well as the resolution A selection of measurement speeds is listed in Table AA 5 The instrument is also rated as to transfer speed the speed at which it can transfer data in bulk to a controlling computer Transfer speed is faster than measurement speed A selection of transfer speeds is given in Table AA 6 As would be expected transfer speed via GPIB is greater than for RS 232 Table AA 5 A Selection of Measurement Speeds Function Digits Readings s DCV DCI 61 2 0 6 0 5 Resistance 61 2 6 5 51 2 60 50 51 2 300 41 2 1000 Table AA 6 A selection of Transfer Speeds This refers to the transfer of data from internal memory Mode ASCII Readings to Rate sec DC RS 232 55 HP IB 1000 AC RS 232 50 HP IB 50 Freq amp Period RS 232 55 HP IB 80 Quick Start The front panel controls are grouped by function Figure AA 5 When the instrument is turned ON it enters DC Voltage mode automatically You are advised to ensure that the Front Rear Input Terminal switch is set for Front A command is entered in response to a menu via push buttons on the front panel The menu is organ ized in a top down tree structure with three levels Figure AA 6 Once into the menu you can move one item horizontally right or left by pressing the gt or uU lt buttons one item down or up by pressing the v AA 10 or buttons respectively
22. d externally to a front panel BNC connector The frequency range of the counter is 0 1 Hz to 10 MHz Input sensitivity is 20 mV RMS 7 Offset 888888 Hz Hz 4 Frequency dial EXT INT 2 Output 50Q 9 VCF input Some Specifications Amplitude Attenuation DC Offset Frequency Response gt 20 Vp p open circuit gt 10 Vp p into 50 Q 20 dB 1 0 dB at 1 kHz lt 10V to 10V lt 5V to gt 5V into 50Q load lt 0 1 dB 0 2 Hz 100 kHz lt 0 5 dB 100 kHz 2 MHz Figure AA 8 A drawing of the front panel of the Instek Model GFG 8016G function generator Quick Start Operation of the instrument is straightforward We shall guide you through selecting a 1 kHz sinewave and connecting the signal generator to the oscillo scope Do the following to turn the Push the ON OFF button 1 AA 12 instrument ON Confirm that the EXT INT buttons 8 are both OUT this will ensure the display shows the frequency of the internally generated signal and not the signal applied externally Depress the appropriate Function button 6 to select a sine wave Manipulate the Frequency pushbuttons 5 and the Frequency dial 4 to select a frequency of about 1 000 kHz NOTE the blinking GATE LED in the display The frequency counter takes about 1 second to compute an average frequency The gate time depends on the frequency To c
23. ddle right shows the ground reference point of the waveform No marker means the channel is not displayed The current marker position should be mid way up the right hand side The Results Area To get your oscilloscope to interpret your waveform and to print the results in the MEAS boxes do the following Press the MEASURE button Press the topmost toggle button to display Source Press the lower four toggle buttons as required one after the other to display CH1 at the top of each box Press the topmost toggle button to display Type Press the lower four toggle buttons as required Specifications and Quick Starts one after the other to display different waveform information period frequency etc Typical res ults are shown in Figure AA 16 which figure your screen should now resemble closely except for the actual numbers Observations and Questions You are now in a position to answer these questions about your waveform Is the displayed Period value the inverse of the displayed Frequency value Is the displayed Cyc RMS value meaning rms value calculated over one cycle equal to one half the displayed Pk Pk value divided by the square root of 2 Can you speculate on why the answer to the prev ious question might not be yes For the Programmer Communication The instrument supports communication and control via both RS 232 and GPIB ports Connectors are located on the rear panel Maximu
24. e Type CH1 Period 1 85 ms CH1 freq 540 0 me Figure AA 15 A closeup of the oscilloscope display showing the five menu result boxes to the right of the waveform area and the toggle buttons Connecting the Signal Source Assuming you have set up the signal generator as described in the signal generator Quick Start and have connected it to CH1 of the scope do the following Turn the signal generator ON You might immed iately see a sinewave on the oscilloscope display If you do continue with step If you do not AA 17 Specifications and Quick Starts then do the following Press the CH1 Menu button once or twice until you see the sinewave Press the MEASURE button Press AUTOSET gt The MEASURE state You can think of the MEASURE state as the home state of the oscillo scope the state in which the oscilloscope displays numerical results in the result MEAS boxes and the state in which the word MEASURE is printed above the topmost box on the right hand side of the display To minimize confusion you should return your oscilloscope to the MEASURE state whenever you change an item in a menu Going to the MEASURE state is easy just press the MEASURE button Displaying Removing a Trace At this stage you should have only the CH1 signal showing since the CH2 signal is zero or just noise If you do not see the CH2 trace continue with step If you do see the CH2 trace do the following Press the
25. e nnnnA Set Auto Print Feature to nnnn nnnn 0 turns feature OFF nnnn C output is continuous C Begin span calibration L Begin linearity calibration xM Place balance in unit x nnnn S output on stability nnnn 1 3600 sets auto print interval x 0 gram x 1 ounces x 2 troy ounces x 3 pennyweights x 4 parts counting x 5 pounds T Same effect as pressing Zero On V Print software version EscR Resets setup and print menus to factory default Resets RS 232 configuration P Print display data LE Shows last error code Response Err Error Number xS Print stable data only Where x 0 for OFF x 1 for ON Data Format character space and takes up a maximum of 6 The balance outputs a frame of 22 bytes inclusive of the lt CR gt lt LF gt at the end The structure is explained in Figure AA 2 The response string consists of two parts a numeric part and a unit part The numeric part begins in the 7 AA 4 character spaces One space separates the numeric part from the unit part The unit part occupies at most 3 character spaces Preparation for Remote Control The balance is ready for student use and for remote control via LabVIEW No special preparation is neces sary if the student drivers listed in Chapter 5 are used The balance has been left with the factory defaults For exploratory reasons the balance has been run at a baud rate of 9600 but higher than the default baud rate has been found to result in unreliable opera
26. e interfaces supported It is anticipated that very soon the standard serial and GPIB interfaces will be replaced by universal serial bus USB and IEEE 1394 or Fire Wire interfaces At present the parallel printer port on Windows PCs is often used with lower end or hobbyist data collection devices These printer port devices are long obsolete and will soon disappesr 2 The Tek oscilloscope does not support external control over all values of the RS 232 parameters These are most reliably set manually from the front panel of the instrument before an attempt is made to access the instrument remotely 3 This material was adapted from the document SCPI Technical Backgrounder on the SCPI consortium website http www scpiconsortium org aboutscpi htm 4 Some of these legacy languages are still supported for example Agilent 3478A and Fluke 8840 They are long obsolete and are expected to soon disappear 5 If a Macintosh high speed modem cable is used the RTS line pin 4 on a DB 25 must be disconnected or else the DMM will not send This has the electrical effect of unasserting the RTS line See next note All of the DB 25 Mac cables in the physics lab have been modified in this way Unaccountably the LabVIEW 5 1 VISA VIs do not support control over the modem RTS and DTR lines on a Macintosh If an attempt is made to control the lines via a VISA attribute node an error message is generated 7 This fact is not d
27. e manual It apparently refers to empty string or a failure of the balance to provide a measurement Such returns should be trapped and removed from the data array To avoid this from happening set the baud rate to the 2400 default Sample Rate The sample rate depends on the baud rate At the default rate of 2400 with the instrument prepared to send in response to the P command the sample rate is about 3 per second At the baud rate of 9600 the sample rate is 4 5 per second In continuous mode the sample rate is increased slightly Settings for a Sample Rate of 3 non continuous e Baud rate 2400 for most reliable results e Auto Print OFF e Stable Data Output Only OFF e Use P command Settings for a Sample Rate of 3 continuous e Baud rate 2400 for most reliable results e Auto Print Cont e Stable Data Output Only OFF e Collect data in a tight loop e Since collection may begin in the middle of a data string the first data string should be discarded NOTE The balance does not always respond as ex pected when outputting data continuously When in this state the command to turn Auto Print OFF often has to be sent more than once to take effect Attemp ting to switch from Auto Print Continuous to Auto Print OFF may cause the balance to freeze see caution below regarding freezing Cautions at High Baud Rates If a higher than default baud rate is used the numeric part of the display screen someti
28. e voltage applied to this input the lower the frequency output The voltage applied to the VCF input can be held constant or swept The speed of the sweep is determined by the settling time of the supply Typical frequency ranges obtained with an Agilent program mable power supply on the 8V range providing the controlling voltage are listed in Table AA 8 Some gaps in frequency are the result of the fact that the VCF maximum was 8 volts approximately and not 10 V Using a programmable power supply such as the Agilent the controlling voltage can be swept down as well as up Table AA 8 High limit low limit frequencies obtained with voltage VCF inputs of 0 02 V and 8 22 V approximately To obtain this data the frequency control of the signal generator was kept at maximum fully clockwise on the range indicated Range High Limit Low Limit 1M 2 1 MHz 450 kHz 100k 210 kHz 45 kHz 10k 21 kHz 4 6 kHz 1k 2 1 kHz 460 Hz 100 200 Hz 46 Hz Some trial and error is required to find the best frequency range of the generator for the sweep range desired Attention should be paid to the issue of linearity i e how linearly does the frequency output depend on the voltage applied to the VCF input A calibration curve should be prepared AA 13 Specifications and Quick Starts Telulex Model SG 100 A Signal Generator This instrument will likely be used only for projects or practice programming General Description The Telulex Model SG 10
29. e width specified It is antici pated you will probably not use binary transfers in this course in any case for more information see the manual Though binary transfers are faster and more efficient in terms of memory usage than are ASCII transfers they are trickier to program Beginners are strongly urged to use ASCII format Agilent Model E3640A Programmable Power Supply General Description The Agilent Technologies Model E3640A program mable power supply Figure AA 18 is of late 1990s technology It is a single output dual range 30 watt supply It has two ranges LOW 0 to 8V 0 to 3 A and HIGH 0 to 20V 0 to 1 5 A It can function as a constant voltage CV source or a constant current CC source and will automatically switch from the one source type to the other depending on the load resistance Voltage and current limits may be set independently It has over voltage OVP protection and 5 memory locations for the storage of settings A relatively short settling time makes the instrument ideally suited for studies of the electrical characteris tics of devices over a range of voltage while minimizing device self heating A major feature of the instrument is that two or more supplies can be connected in series or in parallel to provide various voltages and currents Figure AA 18 The Agilent Model HPE3640A programmable power supply 1 Low Voltage Range Selection key 2 High Voltage Range Selection key 3 Overvoltage
30. eadable The command sequence breaks down as follows M0 Set 625 to Sinewave mode F1 Move cursor to field 1 frequency fisld 3 141Z_ Enter a frequency value of 3 141 MHz N Move cursor to next cursor field field 2 level field 2 3Z Enter a level of 2 3 dBm FO Move cursor to field 0 turn cursor off Peculiarities The fact that the execution of each command string is signalled by the return of a gt character means that these characters have to be meticulously removed from the serial buffer in software This task is performed by the student drivers listed in Chapter 5 Tektronix TDS 210 Digital Oscilloscope The Tektronix TDS210 digital oscilloscope was the least expensive of the TDS2xx series oscillo scopes that Tektronix marketed This oscilloscope is therefore ideally suited for student use in a teaching laboratory What you learn on this DSO you can apply to any other more modern instrument of its type and from any number of manufacturers General Description The Tek TDS210 digital oscilloscope Figure AA 12 is marketed with three optional extension modules The description here applies to the basic oscilloscope with the TDS2CM Communications module installed This is the configuration of all of the oscilloscopes in the physics lab This module provides hardcopy output and communication via the RS 232 and GPIB ports more on this below The oscilloscope can perform 1 GS s of 8 bit resolu y O
31. h are selected by the Function button To see what these modes are do the following e Push the Function button slowly about 10 times and observe the mode names as they appear each time on the LCD screen The modes are A H D H MIN MAX REL MEM RCL DUAL COM CMP After CMP the meter will revert back to the A H mode e Put the DMM into any mode you like and then turn the DMM OFF and ON Observe that the DMM will always revert to the A H mode on boot up Most of these modes will not concern us here and so we restrict our description to the two most important A H stands for Auto Hold In this mode the DMM shows in its secondary display the reading taken 4 seconds earlier This is the power on mode and therefore the mode you will use most often in this course COM In this mode the DMM sends data contin Specifications and Quick Starts uously out the RS 232 port when the DTR line is set high This mode should be used only in special circumstances for example as part of a project e REMEMBER To quickly reset your DMM to the A H default just turn it OFF and back ON Table AA 4 Selected specifications of the RS DMM Input Impedance is 10 MQ on all DC and AC voltage ranges Function Range Accuracy DC Voltage 200 mV 2 V 20 V 200 V 1000 V 0 8 of display 1 Is digits DC Current 200 pA 2 mA 1 0 of display 1 ls digit 20 mA 200 mA 2
32. h the amplifier s terminal and through ACH1 ACH3 ACH5 or ACH7 depending on which channel pair is selected Figure AA 25 This mode is recommended when any of the following apply e Input signals are low level less than 1 V e Leads connecting the signals to the PCI 1200 are greater than 10 ft in length Specifications and Quick Starts e lt Any of the input signals require a separate ground reference point or return signal e The signal leads travel through noisy environ ments Ground referenced Signal Source Instrumentation Amplifier 1 a ACHO O o 6 AISENSE Vm AIGND Common Vcm Mode Noise Figure AA 24 How to use the NRSE input mode to measure the voltage of a source that has one side grounded Floating Signal Instrumentation Source 2 ACHO Amplifier 2 ACH1 Figure AA 25 How to use the Diff input mode to measure the voltage of a source that is floating wrt ground Differential signal connections reduce picked up noise and increase common mode signal and noise rejec tion With these connections input signals can float within the common mode limits of the input instru mentation amplifier We have chosen to have you use this mode in all analog input measurements you make in this course On the Issue of Gain Even if a sensor has a signal conditioning circuit the signal applied to an analog input line of a DAQ card can vary over the range of millivolts to volts T
33. hort pronounced skippy The idea behind SCPI is that a system controller sends commands or program messages to one or more instruments over a bus and instruments send reply messages back to the controller The reply may be a measurement result an instrument setting an error message and so forth When a program message directly generates a reply it is called a query To give the flavor of SCPI commands a few typical ones are listed in Table AA 1 Such commands are referred to as device specific commands to distinguish them from interface specific commands specific to RS 232 or GPIB already described in Appendix B More SCPI commands are listed in the following sections dealing with specific instruments Table AA 1 A few typical SCPI Commands and Queries Queries terminate with a question mark Command Function ACQuire MODe Queries oscilloscope acquis ition mode CH lt x gt BANDwidth Queries the bandwidth setting of channel lt x gt DISplay STYle DOTs Set display style to dots MATH Return definition of math waveform SCPI commands are based on a hierarchical or tree structure Associated commands are grouped under a common node or root thus forming sub systems A portion of the SOURce subsystem taken from the E3640A power supply command set is listed in Table AA 2 SOURce is the root keyword of the command CURRent and VOLTage are second level keywords and TRIGgered is a third level keyword Essential letters
34. hough most of the time you will want a gain setting of only 1 there will be times when you want to amplify the AA 27 Specifications and Quick Starts signal to take full advantage of the 12 bit resolution of the card Gain settings for bipolar and unipolar opera tion are listed in Tables AA 11 Minimum and maxim um values can be set with the control limits Setting the control limits automatically selects the gain There will be more on this subject in Lab 4 Table AA 1la Bipolar Analog Input Signal Range Versus Gain Gain Setting Input Signal Range 1 5 0 to 4 99756 V 2 2 5 to 2 49878 V 5 1 0 to 8 99951 V 10 500 to 499 756 mV 20 250 to 249 877 mV 50 100 to 99 951 mV 100 50 to 49 975 mV Table AA 11b Unipolar Analog Input Signal Range Versus Gain Gain Setting Input Signal Range 1 0 to 9 99756 V 2 0 to 4 99878 V 5 0 to 1 99951 V 10 0 to 999 756 mV 20 0 to 499 877 mV 50 0 to 199 951 mV 100 0 to 99 975 mV Analog Output Signal Connections The use of the analogue output lines of a DAQ card are arguably of less importance than the analogue input lines To give some examples analogue outputs might be used to provide the retarding voltage in a photoelectric effect experiment or an analogue wave form such as a sinewave Pins 10 through 12 on the I O connector are analog output signal pins Pins 10 and 12 are the DACOOUT and DACIOUT signal pins DACOOUT is the voltage output signal for analog output
35. ick Starts For the Programmer Communication The instrument supports a uni directional RS 232 interface The port is accessed via five small holes on the right hand side of the instrument It takes a non standard connector Figure AA 4 A standard DB 9 connector is fitted to the opposite end of the cable which mates with a Mac cable if used In the figure five lines are shown The numbers correspond to the same numbered pins on the DB 9 i e 2 4 7 3 5 Figure AA 4 Wiring of the serial port on the Radio Shack DMM On bootup the lines may or may not be active depending on the computer since the states of the lines are determined by the computer On a standard Windows PC the TxD RTS and DTR lines are all LOW indicated by red LEDs on an RS 232 indicator box On a tower Mac the TxD and DTR lines are LOW On a Mac or Windows PC laptop no lines are active RS 232 Parameters fixed The following RS 232 values are fixed and cannot be changed Baud Rate 1200 Coding 7 bit ASCII Parity None Stop Bits 2 AA 8 Handshaking None The instrument does not support handshaking but the RTS line must be unasserted or else the DMM will not send The instrument supports no external control beyond a voltage transition on its RxD line meaning send data When in COM mode the DMM sends data continuously as soon as the DTR line is set HIGH ie as soon as G performs a VISA Open see Chapter 5 In this mode
36. ies of electronic balances Figure AA 1 are good examples They feature front panel controls simplified menu automatic shut off multip le weighing units parts counting and a weigh below hook The model described here is number SR6010 It has a 600g capacity and an RS 232 port Figure AA 1 The Ohaus series of electronic balance There are two buttons on the front panel Zero On right and Mode Off left The Zero On button is for turning the instrument on and for zeroing the unit before a weighing operation The Mode Off button is for turning the instrument off and for stepping through menu selections Accuracy Claimed accuracies are readability 0 1g repeatability 0 1 g standard deviation linearity 0 1 g Quick Start To get a measurement from the balance do the following e Assuming the instrument is OFF press the Zero On button momentarily to turn the instrument ON All segments will appear briefly on the LCD display followed by a software revision number 2 0 and then 00 e Note the current weight unit printed at the right hand edge of the display If a different weight unit is desired then press the Mode Off button AA 3 Specifications and Quick Starts continuously until the appears e Before performing a manual weighing the unit must first be zeroed To do this press the Zero On button momentarily e Immediately after zeroing place the object to
37. ill print an OL in the display meaning overrange There are 5 ranges of voltage and current AA 6 Sockets Four sockets designed to accept a standard banana plug are arrayed along the bottom sector of the panel These are labelled 20A mA COM and V Q You will not be using the 20A socket in this course On the other hand you will always use the COM socket otherwise known as the COMMON or GROUND connection in all measurements you make excepting capacitance To measure current use the COM and mA sockets to measure resistance or voltage use the COM and V Q sockets There are also two sockets for measuring capacitance Specifications Radio Shack claims the DMM has good voltage and current measuring characteristics meaning that when operated as a voltmeter it has a very large internal resistance 10 MQ and when operated as an ammeter it has a very small internal resistance 10 1000 Q depending on the range Specifications are listed in Table AA 4 All measurements have an uncertainty associated with them How to calculate this uncertainty is explained in Example Problem AA 1 Quick Start To turn the instrument on push the POWER button The display should come alive If the battery is weak a LOW BAT sign will appear in the display If the LOW BAT sign does appear call your instructor the battery will need replacing The instrument has a number of modes whic
38. ing in principle for four input lines One line of each port is called the Input Voltage Line the other the ID Input Line Which of the two lines gets read is controlled by the DTR serial line Normally with the DTR line high by default unasserted the Input Voltage line is read To read the ID Input lines the DTR line must be set low in software asserted ae met Figure AA 19 The SBI box showing Port 1 and Port 2 The signal on a line selected is digitized to 12 bits and output on the serial line in two 8 bit bytes The operation is called word formatting The lower six bits of each 8 bit byte is the data sent in low byte high byte order The higher two bits of each 8 bit byte identifies the origin of the bytes the Input Voltage line or the ID Input Line Thus each data frame con sists of four 8 bit bytes Frames are sent continuously with no special indicator of the beginning or ending of AA 24 a frame Technical Details The ADC in the SBI box is a Linear Technology LTC1290DCN 12 bit switched capacitor successive approximation type with 8 inputs and an on chip multiplexer Only 4 of the 8 inputs are actually used here PLD The actual serial word formatting as described above is performed by an AMD PALCE16V8H 25PC 4 The firmware was programmed by Vernier Software engineers Wiring Each port on the box is equipped with a DIN 5 con nector for connecting the sensors Figure AA 20 All Vernier
39. l multimeter the E3640A programmable power supply and the Tek TDS210 DSO on the other hand support remote control over much of the functionality of the instrument that is accessable manually via its front panel controls SCPI Compliance 3 The degree and ease of control of an instrument depends to some extent on whether or not it is SCPI compliant There was until fairly recently a number of proprietary ways of controlling an instrument determined by the firmware shipped with the instru ment At the lowest level of intelligence a hand AA 2 held DMM typically reacts to a voltage transition on its RxD line by sending a standard string of data At the middle level instruments like the Telulex signal generator respond to an arbitrary set of ASCII strings to set modes and to import waveforms At the highest level instruments like the Tek oscilloscope and others produced by leading edge companies like Hewlett Packard LeCroy Keithley Fluke and others respond to a set of commands and queries that have a definite logic and structure to them Just as various consortia have come together to agree on standards of hard ware interfacing for RS 232 GPIB and recently USB and Firewire similar efforts have resulted in a degree of software standardization Software standardization began in 1990 when Hewlett Packard and other companies defined what is now called the Standard Commands for Programmable Instruments or SCPI for s
40. m baud rate via the serial port is 9600 GPIB transfers are observed to be about 2x faster than serial transfers Whatever interface is used communication takes place via commands and queries in the form of ASCII strings with SCPI syntax described above A selec tion of SCPI commands exclusive to this instrument is listed in Table AA 9 As explained above for other SCPI instruments the syntax requires that commands and subcommands in the same branch of a command tree be separated by a colon commands of an unrelated nature must be separated by a semicolon An example of how to combine commands into a single string is explained in Example Problem AA 2 Table AA 9 A Selection of Set Commands and Queries for use with the Tek TDS210 Digital Oscilloscope Command Type Description CH lt x gt Query Returns oscilloscope vertical parameters for channel x Sets waveform data encod ing to ASCII Transfer oscilloscope wave form data DATa ENCdg ASCi Set CURVe Query AA 19 Specifications and Quick Starts Example Problem AA 2 Constructing a Command String for a Tek Oscilloscope Construct as a single command string the instruction to a TekTDS210 digital oscilloscope to transfer the data from channel 1 in ASCII form Solution Certain commands listed in Table AA 9 can be concat enated with a semicolon Thus the command string required is Setting Values of Communication Parameters Unlike the Agilent instruments
41. mes blanks freezes When this happens the instrument often ceases to respond to the Mode Off button it has to be restarted by unplugging and replugging the external power adapter In addition sampling may actual stop briefly in the course of a run It often starts up again after a short time AA 5 Specifications and Quick Starts The Radio Shack Manual Auto Range Digital Multimeter General Description The Radio Shack RS Manual Auto Range DMM Figure AA 3 is one of the least expensive DMMs on the market that has reasonable accuracy 1 2 and a serial port Rade Shack Figure AA 3 The RS multimeter Cat No 22 168A Controls The two most important buttons are the POWER button colored red and the DC AC button These buttons are located on the upper left and upper right hand corners of the DMM s control panel just below the display area The rotary switch in the center of the DMM s control panel is the FUNCTION and RANGE selector With this switch you select the FUNCTION or kind of measurement you wish to make and the RANGE of the measurement There are positions for at least seven types of function resistance OHM area capacitance LO HI voltage V current A and so on There are 7 ranges of resistance 200 Q 2 kQ 20 KQ 200 kQ 2 MQ 20 MQ and 2000 MQ On the 200 Q range the DMM will display a maximum of 200 Q if the resistance exceeds this value the DMM w
42. n be accessed in PDF format via the course web page and via some of the web pages of the manufacturers Digital Instruments The instruments used in this course are nearly all digital instruments They possess in their circuitry an analog to digital converter or ADC described in Chapter 3 To put the point simply here an ADC samples an analog waveform at an instant of clock time and converts the voltage to a number and does this repetitively at successive equally spaced clock times For the topics of conversion and instrument communication see Chapters 3 and 6 Here we focus on the instruments themselves the kinds of measure ments they make and their strengths and weaknesses Four important considerations among others distinguish one instrument from another acquisition speed display capability storage capability and control capability Before launching into details of the first instrument we shall spend a few moments elaborating these four points Acquisition Speed For a discussion of the topic of sampling see Appendix E Here we shall think of sampling as simply measurement The rate at which instruments sample or measure varies greatly and is for the most part determined by cost The Radio Shack DMM costs 99 AA 1 Specifications and Quick Starts and samples once each second 1 S s The Tek TDS210 digital storage oscilloscope DSO costs 1500 and samples at the maximum rate of 1 000 000 000 per second 1 GS s at 8
43. ns and Quick Starts acHo 1 2 achi acH2 3 4 ACH3 AcH4 5 6 ACHS ACHe 7 8 ACH7 AISENSE AIGND 9 10 DACOOUT aan 11 12 DACiOUT DGND 13 14 Pao PA1 15 16 PA2 PA3 17 18 PA4 pas 19 20 pag PA7 21 22 PBO PB1 23 24 PB2 pB3 25 26 PB4 Pes 27 28 PBe PB7 29 30 Pco pci 31 32 pce pc3 33 34 pca Pcs 35 36 pce pc7 37 38 EXxTTRIG EXTUPDATE 39 40 EXTCONV ouTBo 41 42 GATBO OUTB1 43144 GATB1 CLKB1 45 46 OUTB2 GATB2 47 48 CLKB2 5V 49 50 DGND Figure AA 21 Pinout of the PCI 1200 DAQ card connector Selected Specifications for Analog Input Number of channels 8 single ended 8 pseudodiffer ential or 4 differential software selectable Type of ADC Successive approximation Resolution 12 bits 1 in 4096 Max sampling rate 100 kS s Input coupling DC Overvoltage protection 35V power on 25V power off Input Impedance Normal power on Power off Input bias current 100GQ in parallel with 50pF 4 7 kQ min 100 pA Types of Signal Source Signal sources are described as being of two types floating and ground referenced Floating Signal Source A floating signal source is one that is not connected in any way to the building ground system but has an isolated ground reference point Some examples of floating signal sources are chemical cells the outputs of transformers and thermocouples The ground reference
44. o more than 10 Table AA 8 Practical sample rates achieved with the example program HPMVoltageLogger vi Chapter 5 Range Resolution Sample Rate 0 1 41 2 30 0 1 51 2 26 0 1 61 2 5 A MEAS MENU gt B MATH MENU gt C TRIGMENU gt D SYSMENU gt E I OMENU gt _ F CAL MENU Figure AA 7 The top level menu items Use chemical cell AA 11 Specifications and Quick Starts Instek Signal Generators Models GFG 8016G and GFG 8216A Three models of signal generator are available for use in this course the Good Will Instek Model GFG 8016G or Model GFG 8216A for general use and the Telulex Model SG 100 A for special projects We describe here the GFG 8016G the Model GFG 8216A is very similar General Description This instrument Figure AA 8 is manufactured by Good Will Industries Taiwan It is a combination sig nal generator and frequency counter It provides sine triangle square TTL pulse and CMOS waveforms over a frequency from 0 2 Hz to 2 MHz in 7 ranges It has a standard 50 Q output 10 a variable DC offset and a voltage controlled frequency VCF input 5 1 Frequency pushbuttons ON OFF Function buttons 1M 100K 10K square triangle sine GW Function Generator Frequency accuracy is 5 and sinewave distortion is claimed to be less than 1 from 0 2 Hz to 200 kHz The instrument has a built in frequency counter 6 digit display that can be used to read the internally generated signal or a signal applie
45. ocumented by Radio Shack or by Metex Corporation the OEM of the instrument Agilent Technologies is a subsidiary of the Hewlett Packard Company For more information on Agilent and Hewlett Packard products log onto the Hewlett Packard website www hp com Telulex was acquired by Berkeley Nucleonics Corp BNC You can obtain more information from the BNC website www berkeleynucleonics com These oscilloscopes were purchased in 1997 the year they first came on the market 11 These extension modules are the TDS2HM Hard Copy Module the TDS2CM Communications Module and the TDS2MM Measurement Module The TDS2CM Module also provides the functionality of the TDS2HM Module 12 In fact both ports can in principle be used alternately by one or two computers see Lab 3 Both ports cannot be accessed simultaneously Attempts to do this have failed 13 Tektronix claims a maximum baud rate of 19200 However attempts by the author to communicate at this rate have failed except for reception of instrument ID In spite of Tek s claim the maximum reliable baud rate appears to be 9600 14 These commands and queries were selected from the Tektronix TDS2xx series Two Channel Digital Oscilloscope Programmers Manual 070 9576 02 15 Another problem exists in using LabVIEW VISA functions with the SBI box on the Macintosh The VISA functions in LabVIEW 5 1 do not support manipulation of the handshake lines An attempt to assert the DTR line returns an erro
46. of a floating signal source should be tied to AIGND to establish a local or onboard reference for the signal Instrumentation Amplifier Vm Measured Voltage Vm Vin Vin GAIN Figure AA 22 Each of the 8 signals appearing at the 8 analog input channels passes through a multiplexer and then into an opamp instrumentation amplifier Ground Referenced Signal Source A ground referenced signal source is one that is connected in some way to the building system ground and is therefore already connected to a common ground point with respect to the PCI 1200 assuming that the computer is plugged into the same power sys tem Examples of this kind of source are nonisolated single ended outputs of instruments and devices that plug into the building power system i e outputs of simple power supplies and signal generators literally any instrument with a BNC coaxial output connector Analog Input Channels The 8 input lines or channels can be configured as 8 single ended inputs or as 4 differential inputs accord ing to the input mode selected There are 3 analog input modes called RSE Input NRSE Input and Diff Input We spend a few moments describing each 1 RSE Input Eight Channels Reset Conditions RSE stands for Referenced Single Ended RSE input should be used if the source of your signal is floating with respect to ground RSE means that all input sig nals are referenced to a common ground point that is tied to the
47. on nected to the output of the supply has been removed Turn the power supply ON by pressing the Power button on the left side of the panel The power supply will go into the power on reset state In this state the output is disabled the OFF annun ciator turns on its low voltage range is selected and the OVP annunciator and low voltage range indication annunciator turn on for example the 8V annunciator turns on for the E3640A model and the knob is selected for voltage control Push the Output On Off button to enable the output The OFF annunciator turns off and the CV annunciator turns on The instrument is now in AA 22 meter mode This means that the display shows the actual output voltage in volts and the output current in amperes Rotate the knob clockwise and then counterclock wise to confirm that the front panel voltmeter responds as you would expect With no load connected the ammeter should indicate nearly zero Push the High button to switch to high voltage 20V range and repeat When you are satisfied the supply is working correctly go back to the Low voltage range and a voltage of 0 00 V Current Output Checkout You can confirm the power supply s current function by the following procedure Start with the instrument OFF Turn the instru ment ON Connect an insulated banana cable across the output and terminals Enable the output The CV or CC annunciator will tu
48. ontinue Ensure the Amplitude control 3 is midrange with the indicator straight up and the attenua tion OFF If necessary push the amplitude control IN to turn off the attenuation Ensure the DC OFFSET control 7 is midrange or OFF A DC offset refers to a DC voltage added to the AC output which is not wanted here Connect the 50 Q OUTPUT of the generator 2 to CH1 of your oscilloscope with a BNC coaxial cable This cable s construction is illustrated in Figure AA 9 The signal is carried on the cable s central conductor The braided shield is ground which connects to the outer casing of the cable end BNC cable has twist lock connectors at both ends so take care when connecting the cable to the signal generator and oscilloscope Braided shield ay j ve yp ai N Inner insulation Central conductor TB Outer covering Figure AA 9 The composition and symbol of coaxial cable For the Programmer This instrument has no RS 232 or GPIB port and therefore does not support the kind of communication Specifications and Quick Starts described for other instruments here However it does have a voltage controlled VCF input Voltage Controlled Frequency The frequency output of the generator can be controlled by a DC or AC voltage applied to the VCF input 9 This voltage can be varied between 0 and 10 volts or 10 and 0 volts The frequency is swept down meaning the higher th
49. or reference or comparison purposes To transfer a CH1 signal first press the SAVE RECALL button For Source select CH1 for REF select A then press Save If the REFA button is On the REFA signal will be displayed in light pen along with the CH1 signal Figure AA 13 in dark pen The REFA signal will con tinue to be displayed until you press the REFA button Off tHe Si im Rela ziii 2S CHT Aiie Figure AA 13 A hardcopy from the oscilloscope showing the current CH1 display dark pen and the previously saved waveform in Ref A light pen The RefA waveform scaling is shown in the lower left hand corner of the display Specifications and Quick Starts Quick Start Before attempting to measure anything with your oscilloscope it is useful to make your way through the following activities First Boot Turn the oscilloscope ON NOW if you have not done so already When the oscilloscope boots it performs diagnostics and prints the results to its LCD screen If anything is amiss if a message states something has FAILED a test alert your instructor After a second or two the screen should clear The LCD screen has two recognizeable areas a larger square area for displaying waveforms and a smaller rectangular area to the right of it with five measure MEAS boxes for displaying menu selections and numeric results You select from menus by pressing the toggle buttons shown in Figure AA 15 Sourc
50. pply to plot the zener diode s current vs voltage characteristic in the reverse direction Describe how you would set the current limiting on the power supply to do this Solution If the zener can dissipate no more than 0 5W at its breakdown voltage of 6 2V then at 6 2 V it should pass a current of no greater than Pax _ 05W _ max 81mA mx VO EAV Thus to ensure the zener does not self destruct the current should be limited to about half of the maxim um current or about 50 mA This value though somewhat arbitrarily chosen will achieve the desired result Specifications and Quick Starts For the Programmer Communication The instrument possesses both RS 232 and GPIB inter faces though only one interface may be used at a time and that interface must be set via the front panel Default GPIB parameters Address 5 Possible values of the RS 232 parameters Baud Rate 9600 factory setting Coding 8 data bits Parity None Start Bits 1 fixed Stop Bits 2 fixed Handshaking CTS DTR fixed This instrument is unusual in that handshaking can not be turned off Changing Settings We shall assume you have worked your way through the QuickStart To confirm the GPIB RS 232 parameters part of Lab 3 do the following Turn the instrument ON Press the I O Config button If GPIB 488 is displayed rotate the knob until RS 232 is displayed Hold down the I O Config bu
51. put It is a hardwired version of the main output and is available in all modes The SYNC Out swings 0 V to 5 V and is useful for driving digital circuitry Quick Start Modes of operation are changed frequencies entered etc by pushing buttons on the keypad To give you the flavor of what is involved we describe how to enter a waveform and how to set a frequency Do the following The ON button is located in the lower left hand corner of the panel Push this button to turn the instrument ON When the instrument boots it performs diagnostics and loads an initialization from non volatile RAM This information is printed to its LCD screen Wait a few moments for this to complete The unit defaults to generating a 1 000000 MHz sinewave at a level of 10 0 dBm roughly 2 2 volts peak to peak into a 50 Q load To change the frequency press the Next Cursor Field N button once The cursor will move to the frequency field The cursor position is indicated by a flashing digit You can change the frequency two different ways 1 by entering a new value and 2 by modifying the current value To enter a new value type in the frequency using the numeric keypad Then press the MHz Z KHz Y or Hz X key to set the frequency units The instrument will make a double clicking sound to indicate that a new frequency value has been accepted For practice try entering a frequency of 2 000000 MHz For the Programmer Communication
52. r see note 7 16 8 This description is drawn from the National Instruments PCI 1200 User Manual and the Data Acquisition Basics Manual Both manuals are available in the physics lab for short term borrowing AA 30
53. ransfers in this course CH1 CH2 gt MATH REFA REFB Oscillo Computer scope REFA REFB Figure AA 14 Transfers supported between oscilloscope and computer Data Format Waveform data uses one 8 bit data byte 18 to repres ent each data point regardless of the acquisition mode The oscilloscope can transfer waveform data in either ASCII or binary format Use the DATa ENCdg command to specify one of the following formats e ASCII data is represented by signed integer 18 values The range of values depends on the byte width specified One byte wide data ranges from 128 to 127 Two byte wide data ranges from 32768 to 32767 Two byte wide data capability is included for compatibility with legacy products One byte wide data is recommended for maxim um efficiency and transfer speed Each data value requires two to seven characters This includes one character for the minus sign if the value is negative one to five ASCII characters for the waveform value and a comma to separate data points An example of an ASCII waveform data string is the following CURVE lt space gt 110 109 110 110 109 107 10 9 107 This kind of file is often called a Comma Separated Value CSV file For an example of a CSV file see Chapter 4 e Binary data can be represented by signed integer or positive integer values The range of the values Specifications and Quick Starts depends on the byt
54. rn on depending on the resistance of the test lead You will likely see something like 0 00V 0 000A displayed The display is in meter mode Set the display to the limit mode by pressing the Display Limit button the Limit annunciator will flash By means of the knob adjust the voltage limit to 1 0 volt to insure CC operation The CC annunciator will turn on To go back to meter mode when you have finished this task press the Display Limit key again or let the display time out after several seconds With the display in meter mode from step turn the knob clockwise and then counterclock wise to confirm that the ammeter responds to knob control and that the voltmeter displays near ly zero the voltmeter displays the voltage drop across the test lead You should see the instru ment switch from CV to CC and back again IMPORTANT If you wish you can change the digit that flashes by turning the knob To change this press the resolution selection keys lt or gt appropriately Turn off the power supply and remove the short CAUTION If used carelessly this instrument has the capacity to quickly destroy a component connected to it To illustrate the caution you should exercise we consider an example Example Problem AA 3 Setting the Power Supply s Current Limiting You are given a zener diode type 1N375 which is described as a 6 2V zener of 0 5W power rating You are to use the power su
55. te control commands and prints error messages to the display This greatly assists in debugging Serial Port Wiring This instrument is a DTE the serial port connector is a standard male DB 9 It is shipped with a null modem cable Device Specific Commands This instrument responds to a host of device specific commands A selection of the more useful is listed in Table AA 7 Table AA 7 A Selection of Device Specific Commands Command MEAS VOLT DC 10 0 003 MEASure Diode Preset and make a diode measurement Storing Outputting Data The programmer has the choice of having the meter record data at high speed and save the data to internal memory or of streaming the data continuously in Specifications and Quick Starts response to the Read command out the RS 232 or GPIB ports With the former choice the programmer is limited to 512 measurements whereas with the latter there is no such limitation For many projects in physics it is found to be desireable to limit the resolution to 4 1 2 digits for the highest speed and to stream the data over the RS 232 or GPIB port and collect it by means of a tight loop The user may collect as many readings as needed and may stop the acquisition at any time Some sample rates actually obtained are listed in Table AA 8 These were obtained using a single copper constantan thermocouple as the voltage source The sample rate at 41 2 and 5 1 2 digits of resolution typically differ by n
56. tion more on this below Data can be sent from the balance in either of two ways continuously or in response to the P command Table AA 3 If the highest speed is required then the balance should be run in continuous mode read buffer s s s s s s S300 2 sg s s s s s s r n read buffer s s s s s s10 590 soz s s s s s r n read buffer s s s s s s s9 650 sozt s s s s r n Figure AA 2 Three example responses from the Ohaus Scout II balance for the calibration mass of 300 gram supplied with the instrument grams top ounces middle and troy ounces bottom Peculiarities of the Balance The programmer should be alert to the following peculiarities of the balance e Whenever a VISA Open is executed with the balance connected to the serial port the balance performs a zero automatically There is no need to zero the instrument as part of an initialization sequence e If the balance is set to output continuously or is set to output in response to the P command and if the printing of unstable data is enabled then the balance will insert a question mark in place of the last space character in the return string of unstable data as for example s s s s s s 269 9 sg s s s s s r n This question mark can be used to flag data of questionable accuracy Specifications and Quick Starts e At the baud rate of 9600 there are times when the instrument returns the string ES r n This occurrence is not documented in th
57. tton and rotate the knob until 9600 Baud appears in the display AA 23 Specifications and Quick Starts The Vernier Software SBI Box The Vernier Software serial box interface SBI is an example of a free running serial digitizer A free running digitizer is one of the simplest types of digitizing devices in that it is a device over which there is no computer control It is a device that is always operational and sending data so long as power is applied to it It is commonly a device built from a very simple circuit of low speed and therefore inexpensive A glance through the electronics hobbiest magazines Poptronics Electronics World and others will reveal the existance of a number of these devices on the market Many are designed for the parallel printer port on a Windows PC while others have a serial port and work on any platform We discuss here an example of this latter kind of device This instrument has been used for data acquisition in the first year physics lab at UTSC for 15 years Though very simple and inexpensive it provides an interesting and challenging problem in programming for the ardent student of computer science General Description This device Figure AA 19 is called the Serial Box Interface or SBI box for short It is marketed by Vernier Software for use in education The box is equipped with two ports Port 1 and Port 2 each capable of supporting two analog 0 5V input lines thus mak
58. uses 82C55A PPI Compatibility TTL 0 3V lt Input Low lt 0 8 V 2 2 V lt Input high lt 5 3 V Output Low lt 0 4 V 4 V lt Output high 0 5 to 5 5 V power on Number of channels Digital logic levels Protection 0 5 V power off Power Connections Pin 49 of the I O connector supplies 5V from the computer s power supply via a self resetting fuse The fuse will reset automatically within a few seconds after the overcurrent condition is removed Pin 49 is referenced to DGND and the 5V can be used to Specifications and Quick Starts This concludes our description of the PCI 1200 DAQ card The four major functions of the card analogue I O and digital I O are explored in Lab 4 power external digital circuitry or low power sensors Power rating 1A at 4 75 to 5 25 V Practice Problems The Radio Shack DMM and Agilent 34401A DMM are both used to measure the voltage of the same chemical cell The results are as follows Show by means of uncertainty calculations that the measurements of these two devices agree to within the experimental uncertainties or they do not You are given the following instruments an RS DMM TekTDS210 DSO DAQ board Explain in one paragraph how you would use these instru ments to measure the output from i a chemical cell and ii a K type thermocouple AA 29 Specifications and Quick Starts EndNotes for Appendix A 1 The industry is changing rapidly in regard to th
59. ut lines ACHO ACH7 2 12 bit digital to analog DAC output lines DACOOUT DACIOUT 24 lines of TTL compatible digital I O PAO PA7 PBO PB7 PCO PC7 and 3 16 bit counter timer lines for timing I O These lines are made to terminate in a breakout box to assist the user in connecting the lines to external signal sources and sensors In Lab 4 you will begin your study of the card with the analog input channels so we begin our description here with them Instrumentation Amplifier Each analog input channel is connected through an instrumentation amplifier Figure AA 22 An instru mentation amplifier is essentially an opamp described in Chapter 2 with non inverting and inverting inputs The amplifier applies a selectable gain common mode voltage rejection and high input impedance to the analog input signals A common mode voltage is an undesireable electrical noise that appears in equal measure at both inputs Signals are routed to the and inputs of the amplifier through input multiplexers The amplifier converts the two input signals to a signal equal to the difference between the two input signals multiplied by the amplifier s gain setting The amplifier output voltage is referenced to the PCI 1200 ground The PCI 1200 ADC measures the output voltage by performing an analogue to digital A D conversion How the inputs are wired is determined by the mode selected more on this below AA 25 Specificatio

Appendix A Specifications and Quick Starts

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