Thurlby DSA524, Operating Manual

Page 1: ...Thurlby DSA524 digital storage adaptor OPERATING MANUAL AND TUTORIAL V2 0 ...

Page 2: ...anual applies to units with a firmware level of 2 71 and above IT IS VERY STRONGLY RECOMMENDED THAT NEW USERS START BY FOLLOWING THE TUTORIAL INDEX Title Section Page REFERENCE SECTION Connecting an Oscilloscope R1 2 Setting up the Display R2 2 Front Panel Controls R3 2 Escape and Reset R4 2 Controlling Digitising R5 2 Timebase Setting R6 2 CH1 and CH2 R7 3 Digitising Memories R8 3 Trigger R9 3 Tr...

Page 3: ... NN the key will enter the number printed alongside it Note that when SHIFT or a function ending in NN is pressed the lamp marked ENTER will flash to indicate that one or more further key presses is required Any function that causes the ENTER lamp to flash can be cancelled by pressing that function key again Note that some of the functions including SET SCOPE automatically set the RUN HOLD functio...

Page 4: ... TRIGGER RATE ABOVE 1MHz and the DSA will beep to indicate that the timebase speed may need to be set faster R7 CH1 AND CH2 The two input channels are identical The input sensitivity is variable between 10V and 2mV per division The maximum bandwidth is 35MHz down to 20mV div 20MHz at 10mV div 10MHz at 5mV div and 5MHz at 2mV div The volts per division keys autorepeat if held The input coupling can...

Page 5: ... is automatically increased or decreased to maintain a constant time delay when the timebase speed is changed within a limit of 9 999 divisions maximum PRE there is no equivalent to pre trigger on a real time oscilloscope Pre trigger allows the part of the waveform which occurred before the trigger to be stored and observed The maximum pre trigger delay is 40 divisions Pressing either key shows th...

Page 6: ...unaffected R12 INDEXED WAVEFORM MEMORIES The DSA524 has sixteen 1K word memories for temporary or permanent storage of waveforms Each memory is identified by a two digit number from 01 through to 16 The memory is sup ported by trickle charged Ni Cad batteries which will remain charged for several months should the unit be left unpowered To store a waveform in an indexed memory obtain the required ...

Page 7: ...not captured the first section of the waveform captured starts 350 nanoseconds after the trigger event b Display Update Rate Repeat mode involves complex manipulation of data which can take several seconds per digitisation The display update rate varies between about one per second for a single channel at 2usecs div to one every 10 seconds for both channels at 50nsecs div The Rate key is disabled ...

Page 8: ...hen overflows could occur on the multiplied waveform The displayed waveform is limited to 4 25 divisions and conse quently 3 divs multiplied by 2 5 divs will be displayed as 4 25 divs instead of 7 5 divs The AxB function cannot operate while digitising is taking place Pressing the AxB key will set RUN HOLD to HOLD The function multiplies the traces exactly as they appear at the moment that the AxB...

Page 9: ... show baud rate 9600 for example Use the reference cursor keys keys 2 and 3 to increase or decrease the rate then press ESCAPE If the DSA is not connected to an oscilloscope the baud rate may be set directly using the FUNCTION NN key see Section R27 Note that as well as the options of 300 through to 38 400 there is a further option of IEEE This option is exclusively for use when the optional IEEE ...

Page 10: ...g SHIFT followed by RESET and with the signal generator being set to SINE 20kHz 5V pk pk INDEX TO THE TUTORIAL Page Equipment Required 10 Setting up the Equipment 10 First Steps 10 What to Expect 10 The Display Oscilloscope 10 Front Panel Controls 10 Getting out of Trouble 10 Part One The Basic Functions Controlling Digitising 10 Controlling the Input Channels 11 Controlling the Traces 11 Setting ...

Page 11: ...the display is made up of discrete steps waveforms do not look quite the same as they do with an analog oscilloscope The minimum level change between samples is one thirtieth of a division and even where the input signal level is constant the digitised level may vary slightly This variation is caused by noise on the signal noise in the input amplifiers or digitising noise in the ADC typically bit ...

Page 12: ...es on the screen and provide 4 25 divisions of adjustment Press the key marked HOME VAR to enable variable posi tion it is enabled when the lamp is off Try varying the position of the traces note that whereas OFFSET only affects the waveform when digitising is taking place PO SITION affects it at all times whether RUN HOLD is at RUN or HOLD Press the key again to home the trace position 2 The GAIN...

Page 13: ...els are on the ALT lamp illuminates for speeds of 10us div and faster and that the CHOP lamp illuminates for speeds of 20us div and slower CHOP indicates that both input channels are digitised together on opposite cycles of the sampling clock while ALT indicates that the input channels are digitised alternately CH2 followed by CH1 Thus if digitising is un triggered or if the input signals do not h...

Page 14: ... digitising memory captures 4096 words 40 96 divisions per channel The SEARCH key enables the whole of the digitising memory to be accessed It also provides digital magnification by ten using linear interpolation 1 Press SEARCH once the COMP compress lamp will illu minate and a filled bar will appear at the top of the screen for 3 seconds the filled bar represents the 4K of the memory Note that th...

Page 15: ... DSA reset and the generator set to SINE 20kHz 5V pk pk The DSA524 can average any number of readings from 2 up to 255 enabling large improvements to be made to the signal to noise ratio of noisy signals The average number is initially set to 16 1 Turn off Trace B and note the waveform amplitude on Trace A Then remove the trigger signal by setting the source to EXT The waveform should now be unsyn...

Page 16: ...volatile memory and replay them on demand Up to 50 settings can be stored Each front panel setting includes the state of every key and rotary control and the source of each trace waveform Thus if a setting is learned which includes a trace recalled from a wave form store that same store will be recalled again when the setting is re played Thus reference waveforms can be recalled automatically with...

Page 17: ...avoid aliasing Aliasing causes the apparent waveform frequency to be much lower than the real frequency Thus if the timebase is set too low an invalid display will result see Fig a To avoid aliasing the timebase must be set as follows Minimum time div 50 divided by the maximum cyclic signal frequency The difficulties occur when the signal frequency is unknown In this case it is safest to set a fas...

Page 18: ...isplay are plot ted using a level of 100mV div for both Y and X at a rate selec table as 1 2 5 or 10 seconds per division The pen lift signal is normally low to lift but can be inverted To set the plot rate press SHIFT key 8 followed by SET PLOT key 5 The oscilloscope display will show the present plot rate Press one of the REF CURS keys key 2 or 3 to select a new value then press ESCAPE If the DS...

Page 19: ...to have a buffer large enough to accept the data in one stream hand shaking will almost certainly be needed There are two basic types of handshaking hardware handshak ing and X ON X OFF handshaking Both types are provided on the DSA Hardware handshaking uses the RTS and CTS lines of the DSA When the RTS line is set to a 0 a positive voltage level the DSA is ready to receive data when it is set to ...

Page 20: ...trace starting at word N MAG N where N is a decimal number between 0 and 900 This sets the SEARCH function into Magnify mode with the trace starting at word N SROFF This turns any of the SEARCH modes off NORM SLOW or FAST This sets the display update rate ION or IOFF This sets sine interpolation on or off AON or AOFF This sets averaging on or off Example TMB 10uS AON SLOW CR For TRA or TRB the sec...

Page 21: ...ee previous section for an explanation of this command To load the data send the primary command MEM followed by a comma followed by one of the secondary commands listed below followed by a carriage return The secondary commands are as follows ACQ1 or AQU2 This loads the digitising memory of CH1 or CH2 4096 words must be sent TRA or TRB This loads the trace memory of Trace A or Trace B 1024 words ...

Page 22: ...n OSCILLOSCOPE DISPLAY SYSTEM Trace A Displays 1024 words from either CH1 or any indexed waveform storage memory Trace B Displays 1024 words from either CH2 or any indexed waveform storage memory Line Type Selectable as individual levels dots or joined to form a smooth line Update Rate Selectable between 50 per second and Run Mode one every 3 seconds continuous in roll mode OSCILLOSCOPE DISPLAY VE...

Page 23: ... dismantle it S4 FUSE REPLACEMENT The AC power fuse is mounted on the back panel within the AC line input socket housing To replace the fuse pull the clip in tray outwards The active fuse is at the back of the tray the front space is for a spare fuse The fuse must be replaced with a 500mA anti surge 20mm cartridge fuse A ceramic bodied HRC type should be used whenever possible S5 MAINTENANCE AND R...

Page 24: ...Thurlby Electronics Ltd New Road Burrel Road St Ives Huntingdon Cambs England Telephone 0480 63570 Fax 0480 64832 Telex 32475 ...