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1902 mkIV

1. 4 Channes heads tage 4 channel model shown The External Clamp Box Installation This four channel device can be used with any amplifier to prevent input saturation as for instance when high voltages or intense magnetic fields are used as stimuli On receipt of a TTL signal from external trigger equipment it clamps incoming electrode signals for the duration of the trigger signal It can operate in several different clamping modes as selected by a rear panel switch The 2804 External Clamp Box Installing the 1902 software Confidence check Try1902 Connecting the 1902 Running Try1902 Com port and channel number Communications test Installation To install the 1902 operating software autorun the 7902 Support CDROM supplied with the hardware This should be completely automatic under any version of Windows It will install Try1902 a diagnostic and calibration program It will also install the 1902 Control Panel which can be opened by the user to run the 1902 in stand alone mode Once the software is installed you can run Try1902 to check that the 1902 is to the first order working and has not been damaged in transit Before it is run the 1902 must be powered up and connected to your computer With mains power off insert the DC power cable and the RS232 cable into the back of the 1902 The power cable will only plug in one way and the RS232 cable is reversible end for end Make a n
2. How does it work 40 Details of operation The input clamp option CED1902 4 C is designed for use with triggered stimulation of a subject where the stimulus would otherwise overload the isolation amplifier input Such overloads may not be electrically damaging but the amplifier can take several seconds to recover afterwards making it difficult to measure fast responses to the stimulus The types of stimulus where clamping can be useful include fast magnetic field changes and somatosensory stimulus pulses In experimental situations where for example EMG recordings are taken from the hand during magnetic stimulation to the brain clamping is generally not necessary However when very fast responses 1 e 2 10 milliseconds after stimulation are to be measured or recordings are taken from the facial area during stimulation to the head then input clamping can prevent amplifier input saturation and allow these recordings to be made successfully The clamp will not give good results with AC coupling or with the notch filter or high pass filters enabled in the 1902 The clamp input has FET switches that operate at the isolated electrode input They are opened and closed by a timing circuit that is triggered by a pulse at the Trigger 2 front panel input Note that the trigger input is referenced to system ground electrically isolated from the electrodes and that the trigger LED does not need to be set to Trigger2 for a
3. Channel numbers 16 31 1902 communication 14 configuration Setting the 1902 configuration The hardware Wherever there are multiple 1902s the software uses channel numbers to identify which 1902 is being addressed Up to thirty two channels can be set In the 1902 Mk IV channel numbers 0 15 are set by a sixteen way rotary switch accessed through a hole in the back panel Using a 3mm flat bladed screwdriver turn the switch clockwise to increment the channel number The stepping feel is satisfactorily distinct In position 0 and 8 the screwdriver slot is vertical The switch positions are printed on the back panel in hex as a guide If you need to set channel numbers above 15 you must access a switch inside the 1902 See sections on opening the 1902 on page 46 and on the options switchpack on page 51 When the switch OPT 0 is in the off position the rotary switch selects channels 16 31 The 1902 communication settings that is to say the com port number and the channel number s of the 1902 s are stored in the Windows registry in keeping with modern programming practice Formerly this information was stored in a system file named CEDCOND INI These settings only affect communication with the host computer they have no bearing on the function of the 1902 such as the amplifier gain filter response etc Consequently they need only be set once unless you want to rearrange your 1902s in relation
4. EEG unclamped Input ve to inverting input Isolation amplifier Clamped EEG Differential input as with normal EEG 0 5 ms 1 0 ms 12 ms but input is clamped see page 40 for Transducer 14 ms interval selected 10 1902 functional organization The waveform conditioner Digital filter Response The trigger generator General information To the user the 1902 comprises two completely separate functional blocks the waveform signal conditioner and the trigger generator The waveform conditioner provides one channel of output with the input selected via software from a range of input connections There is a comprehensive set of conditioning controls gain selection filtering and offsetting and overrange detection The 1902 may readily be adapted to different specialized signal sources requiring additional control for instance clamping by a choice of internal daughterboards The computer can read back the characteristics of these daughter boards By default digital filtering is installed in your 1902 the alternative being analogue filter sections on a daughterboard The digital filter processing section is based on a 16 bit ADC carrying out conversions at 30kHz this interrupts the microprocessor which carries out digital processing as required before writing the modified data to the DAC which is also clocked at 30 kHz The digital processing imposes a time delay latency of
5. 25 Life support iv Live human subjects 7 43 44 54 55 NOT 28 29 M Magnetic stimulus 40 Mains earth 32 43 46 NOT v 33 43 Mains live 43 Mains neutral 43 Mains plug 16 Mains power 1 32 UK 32 43 Mains frequency pickup 35 Maintenance 45 Mating plugs 16 17 27 Monitor revision number 45 48 Multiple channel setup 37 Multiple channels 34 35 38 Multiple installations 5 13 Index N Noise 26 38 Non disclosure agreement 51 O Offset accuracy 45 Opening 1902 46 Operating system 18 Optoisolator 43 Original packaging 49 Outer case 13 32 Output amplifier 25 programmable signal source 28 trigger pulse 29 waveform 10 Overload indicators 12 25 P PCB CED 1902 02 55 CED 1902 03 56 CED 1902 04 54 CED 1902 20 50 Phase shift 33 38 Plug 4 pin mini DIN 17 6 pin DIN 17 8 pin DIN 17 9 pin D type 31 Power block 1 Powerbox PMP55 32 Printed circuit board 13 Pulse length trigger 29 Q Quad 1902 13 Quad clamp box 4 R Rack mount 1902 13 Radiall SMB 46 51 Rear panel diagram 19 Rear panel connections 16 Recycling 1902 v Reference electrode 35 37 RS232 multi drop 13 serial line 7 S Safety plugs 1 5mm 2 2mm 2 Screened cables iv 31 Sensors high impedance 29 Serial number 45 48 Servicing 1902 49 Shared electrode 36 Sleep recording 23 Socket 4 pin mini DIN 29 6 pin DIN 27 50 8 pin DIN 28 9 pin D typ
6. This is all the more so since with electrodes close to vital organs a very small current can be fatal Consequently the 1902 has provision for an isolation amplifier that has been approved for use with human subjects Electrodes ri yr rigger ransducer Trigger Amp A 99 A Out Out Gate Gate Pos W y 5 i A S i Tri AN rig Trig Ze Overload Neg Ze ma i Power RFI approvals The 1902 has been type tested and found to meet the requirements of the European EN55022 1987 Class B and the USA FCC Part 15 J Class B radio frequency interference specifications when used with the specified power supplies and cables Safety approvals The 1902 meets the safety requirements of BS EN5724 IEC EN60601 1 when used with a CED approved power supply BSI certificate no 221 000018 issued 17 September 1997 Warning The 1902 s isolation approvals may not be relevant to industrial users The unit will run on other power supplies see page 31 but it is important to note that the 1902 does not meet EN 60601 1 1 2000 safety and EN 60601 1 2 2001 EMC standards unless used with the CED approved power supplies 7 Signal input to the 1902 Important General information To amplify signals with the 1902 you must first select the input source and mode of operation The sources are the transducer and the isolated amplifier You cannot use both at once The transducer has four input modes the isolated a
7. power cable socket 16 RS232 port 31 transducer input 28 trigger input 29 Connectors daughterboard bottom entry 52 daughterboard pin headers 52 Molex cable socket 16 suppliers of 17 Continuous operation v Ctrl1902 5 20 AC DC 21 DC rectification 21 during sampling 23 24 filters analogue 21 digital 10 21 gain 20 input select 20 notch filter 21 offset 20 port 20 trigger 22 with CED applications 22 D Data non repetitive 23 repetitive 24 Daughterboards 10 location of 52 nylon stand offs 52 DC power supply voltage requirements 32 DC power switch none 1 16 Declaration of Conformity 61 Differential input 33 Drive capability TTL 29 Dual 1902 13 Dust ingress of v E Earth continuity 32 Earthing strap 46 ECG input 12 ECG lead configurations 27 57 Index EEG input 12 EEG ECG or EMG input 8 EEPROM 18 53 Electric shock 7 43 Electrode box 2 17 34 buffer option 3 Electrodes bipolar configuration 33 ECG 55 independent pairs 37 shared reference 35 36 37 Electrode skin junction 35 Electrostatic discharge 46 52 EMG 37 EMG recordings 40 Equipment digital voltmeter 46 oscilloscope 46 sinewave generator 46 Evoked response recording 24 Exact unity gain 38 External clamp box 4 F Facial recordings 40 Farnell electronic component supplier 17 FCC part 15 J Class B iv 7 Filters DC rectification 10 25 digital 10 12 25 m
8. If you expect that you may revert to your previous configuration you can save the pre existing EEPROM data with the Read from 1902 and Save to disk buttons Serial number Configuration of standard 1902 with no front end board standard filter board and 50Hz Notch filter m Front end Filters Front end fitted Inputs Low pass description High pass description Frontend can be offset 2poleBWorth 2 poleBWorth AC DC select available on front end I Use irtemeeed digital fiering Yassir Settings for analog filters Fixed front end gain i LR hooo HP 1 fico aiji paca Hie LP 2 foo HP 2 jo sti K LP3 fo HP3 f Front end offset range 1 volts a Front end offset range 2 volts Doo Notch filter fitted 50 Hz z Load from disk Program 1902 Read from 1902 Save to disk EEPROM update dialog 53 54 The EEG daughterboard Inside the 1902 The EEG daughterboard designated the CED1902 04 provides medical isolation designed to meet EN60601 1 isolation standards There are several design options for this card that are implemented at board assembly Some options are mutually exclusive so the board is never fully populated Build options include the buffer see page 34 isolated transducer power and the input clamp see page 40 This board is optimized for low noise and a high common mode rejection ratio CMRR which makes it ideal for EEG recording Using the standard model of da
9. The classic example of this and one for which a 1902 is ideal is evoked response recording here segments of brain activity are correlated with recurrent stimuli in order to extract responses buried in the noise During data sampling under Signal all the 1902 s controls are accessible and can be adjusted All settings are recorded with each sweep each sweep can be regarded as a separate data file LK laid File Edit View Analysis Cursor Sample Script Window Help 2c i elm ose Aue w y it me TA Continue z oe EB en 3 ro JT Pause at sweep end Stop Reject Restart BBactive3 crs frame 0 x Port 0 Input Isolated EEG x i Offset Gan i000 4 ee E Trigger C 2 1 Falling edge trigger Filters High pass Low pass 2pole B Worth 2pole BWorth Cutoff 100 Hz Cutoff 500 Hz I AC couple J7 50Hz Notch EMG processing Nowe E Cancel Hep E For Help press F1 1 143 702 0 2694 Frame 1 max 48 0 00 Staeo Flagsoooooooo f I Signal controlling 1902s for multi channel data acquisition 24 Electrical specification Main amplifier The main amplifier comprises a programmable gain amplifier a selectable mains notch filter a programmable selection of low pass and high pass filters analogue or digital and programmable selection of input sources The output of the amplifier is through a standard coaxial BNC socket Bandwidth with ana
10. Unchecking Trigger1 sets Trigger 2 one must always be selected Note that the clamp option see page 40 always uses Trigger 2 when the clamp option is in use Trigger 1 may be used as an independent trigger channel Most users will run the 1902 as a hardware adjunct to a CED 1401 interface operating under one of CED s principal software packages Spike2 or Signal CED applications control the 1902 hardware through an applet similar to the Stand alone Control Panel This appears either with or without an oscilloscope style display on the right The version with the display appears during the setup phase the display assists the user in adjusting gain filtering offset etc It is not a true oscilloscope of course but a digitized simulation using data from the 1401 s ADC analogue to digital converter sampling the appropriate input channel 1902 controls X I Volts Port fo 7 Input Isolated EEG volt i J Offset Gain 1000 7 Oftsel pl volt Irigger 2 1 J Falling edge trigger Filters High pass Low pass 2 pole B worth a 2 pole B worth 7 Cutoff oc Hz Cutoff jal pass Hz I AC couple 50 Hz Notch EMG processing None a 5 volt Cancel Help Control of 1902 setup from CED application 0 005493 volt During sampling the oscilloscope display is not available Access to the ADC cannot be guaranteed quite likely it will be too busy doing other things Also the display generated b
11. approximately 0 35 ms on the data at the time of recording During playback Spike2 or Signal can be configured to remove this delay if required 2 pole or 3 pole digital filters can be applied with either Bessel or Butterworth response The corner frequencies are selected from dropdown lists or users may type in their own values high pass from 0 01 to 1000 Hz low pass from 1 to 10 000 Hz There is a rectification option useful for EMG studies The digital filtering system can also be used to output ADC data down the serial line at up to 100 Hz The trigger generator provides one output channel of pulses derived from a choice of two inputs selected by program It uses comparator circuitry with hysteresis to generate clean TTL pulses from a variety of trigger input sources The Trigger2 input can be used to trigger the EEG input clamping circuit if this option has been fitted see page 40 Electrodes Transducer Indicators Amp out 10 kHz low pass General information Isolated amplifier x100 or x1000 gain x1 to x1000 Notch filter Micro _ controller High pass nl Serial line owas fe i i Overrange Rectify t High pass 10 kHz low pass OUTPUT Waveform signal flow in the 1902 detailing digital filtering subsystem 11 12 Features seen by the user General information Features of the 1902 all selected by program control are Differential or single ended transducer waveform
12. back Inside the 1902 Servicing other than calibration replacing daughterboards and firmware updates should not be attempted by users The 1902 can only be serviced by CED at Cambridge Electronic Design Limited Science Park Milton Road Cambridge CB4 OFE UK Telephone general inquiries 44 1223 420186 Telephone hardware help 44 1223 433477 Fax 44 1223 420488 Email hardhelp ced co uk Ideally the 1902 should be returned to CED in its original packaging which is robust and will protect it against damage Before sending it back e You must first get a returns number from CED e We advise you to dispatch the machine to us CIF CED is not responsible for the safety of the equipment until it is inside our premises e If you are dispatching from outside the EU it is essential to call us for advice on the documentation necessary to get your machine through Customs If you do not provide the correct documentation it may be subject to additional taxes or duties be turned back or even impounded e Include a written description of the problem with the equipment e Make sure the packaging is adequate to avoid damage in transit 49 Inside the 1902 The 1902 The main circuit board in the CED 1902 Mk IV is designated motherboard the CED 1902 20 It has a different computational core from the previous version and uses a Cirrus EP7312 with associated FPGA and flash ROM These are SMT surface mount technology
13. connected to normal AC mains by the standard IEC cable provided There will be a mains plug suitable for your country This power supply can run on any mains voltage from 100 V to 240 V AC 50 Hz 60 Hz There are no switches on the 1902 or the power supply power is entirely controlled by switching at the mains socket The RS232 cable for the 1902 has two 9 way D type connector sockets and is reversible end for end Offer one end to the D type plug marked RS 232 and the other to your computer s RS232 port You will have to inform your application software which port you intend to use see 1 902 communication configuration page 14 Make sure that the jackscrews on both connectors are screwed home to reduce the possibility of radio television interference We expect users to furnish their own input cables for the trigger and transducer connectors for which we supply suitable mating plugs and also their own BNC output cables Details of the front panel socket pin outs are described in the Electrical Specification section below The two outputs from the 1902 trigger and amplifier are brought out through BNC connectors which can be connected using standard BNC cables to measuring and recording equipment such as the CED 1401 Electrode cables A Mating connectors The kit Component The hardware When specified the EEG or ECG electrode inputs will normally be routed through the CED1902 11 Electrode Box see page 2 wh
14. output iso power Vagus 1 The ECG lead configurations are leads I IL MI aVR aVL aVF and V 2 Buffer I O available with the CED1902 4 B buffer option see page 38 Iso power is a factory fitted build option 3 The cable screen is AC coupled to mains earth by 1 nF 6 kV continuous rating 4 Connected to Common except in older ECG 1902s having the right leg drive option fitted 27 Electrical specification Transducer input The 1902 transducer input is an 8 pin DIN socket Input is inherently differential for single ended use the inverting input is grounded The main amplifier offsetting DAC is brought out and may be used as a simple programmable signal source when the waveform conditioner is not required Transducer input 8 pin DIN socket Pin 1902 function Single ended Differential Wire colour Ground Ground Ground es 12 V power 12 V power 12 V power _ oe 12 V power 12 V power 12 V power 4 5Vpower 5Vpower 5Vpower 5 inputtve Input_ Bridge output ve 6 DACoutput DAC output DAC output 7 input ve Linktopin1 Bridge output ve 8 Nocomection To y O Shell Mainsearth Screen Sereen e A human subject must NOT be connected to this socket e The power outputs are intended for driving transducers only Transducers should have impedances greater than 500 Ohms 5 volt or 1200 Ohms 12 volt e Transducer current sh
15. significant bit is set to 1 and the channel number selectable by the rear panel rotary switch will be in the range 16 31 The switchpack is indicated on the diagram on page 50 The other three switches are reserved for future expansion They should be left as they are If you need to change the notch filter frequency a link has either to be closed for 60 Hz or open for 50 Hz This link is indicated on the diagram on page 50 A full set of circuit diagrams can be supplied to authorized personnel on request There will be an administration charge for this service and purchasers must sign a non disclosure agreement 51 Exchanging 1902 daughterboards rN Taking out the old 52 daughterboard Installing the new daughterboard Reassembly Inside the 1902 Open the case as detailed on page 46 Remember to observe precautions against electrostatic discharge earth yourself to the 1902 by a wrist strap and earth the 1902 to mains earth Preferably you should work at a bench topped with conductive plastic The filter module is located just behind the output connector 1902s fitted with digital filters do not have this module installed The front end module is a little way behind the isolated input connector Using a strong plastic pry tool gently lever the circuit board upwards It may help to use a pair of pliers to pinch the split tops of the nylon stand offs to spring the board off the stand offs Ease the board vert
16. the same test connector A 1 pt cross head screwdriver for undoing the outer case A small flat blade insulated trimming tool for adjusting potentiometers A sinewave generator capable of generating 50 or 60 Hz at some 5 V for adjusting the mains notch filter BNC cables and for the 1902 MK IV fitted with digital filters a BNC to 1902 transducer input cable The 1902 circuit board is mounted in an inner can enclosed by an outer case You have to remove the inner can and take off its lid to do the calibration 1 Take due precautions against electrostatic discharge Earth yourself to the 1902 with a wrist strap and earth the 1902 to mains earth 2 First remove power and all cables from the 1902 At each side of the back panel of the outer case is a small black screw Undo these with a l pt cross headed screwdriver Push the BNC connectors on the front of the case so that the inner can slides out by a couple of centimetres dislodging the back panel You can now see that the inner can is also restrained by an earthing strap of green amp yellow wire attached by a small screw Undo the screw and lock washer from the inner can Make a note of the order of these fixings since it is important to replace them the same way see also Reassembly page 52 Slide the bright metal inner can out of the black outer case Remove the lid There are four small screws near the corners of the inner can that hold the l
17. to your computer Once you have used Try1902 to check that your 1902s are working correctly as described in Confidence check above you should use the Try1902 File menu Set port and channels command to save your settings The command opens a dialog box used to set the 1902 communications parameters There are three fields as described below COM port for 1902 communications First 1902 channel to use Search up to at least Saving to the registry The hardware Global 1902 setting This dialog will set the COM port and 1902 channel range in use so that applications such as Spike2 Signal and Ctl1902 will be able to find your 1902s automatically Set the COM port to use for 1902 communications and your first and last 1902 channel numbers If you set the last channel number to Last found the 1902 support will search for 1902s starting at the first channel until a missing channel is detected COM port for 1902 communications Com 6 v First 1902 channel to use Channel 0 Search up to at least Last found 1902 communications dialog box This sets the com port serial line used to communicate with your 1902s Try1902 will set this field automatically so you should not need to change this This sets the channel number used to start the search for 1902s Set this value to the lowest numbered channel that you are using 1902 channel numbers normally start at zero The search for 1902s starts
18. vs time Gain ranges Low noise EEG ECG Gain step sequence Gain accuracy Bandwidth all gains Isolation voltage continuous Isolation voltage peak for 5 sec Input output leakage at 240V 50 Hz Input clamp option Low noise EEG Lead configuration ECG Calibrator ECG 10 GOhm 150 pA 0 3 uV rms 100 dB HIRV less than 10 uV after 1 hour warmup 5 5 uV C 1 5 uV 1000 hrs x1 000 x1 000 000 x100 x100 000 X13 xO 2 DC 10 kHz 1500 V DC 2500 V peak less than 20 uA 0 5 ms 14 ms I II HI aVR aVL aVF and V 1 mV pulse Electrical specification Note wire colours The Wire colour columns in the tables below are for your amp socket drawings convenience if you have to make up cables All 1902 sockets are drawn as the user sees them i e viewed from outside This is also the view of the backs of their mating plugs as seen while wiring them up Isolated input The 1902 MkIV is fitted with a 6 pin DIN socket with a metallic shell that acts as a screen To conform with safety requirements mating plugs must be of the type with a plastic outer sleeve the inner metallic body must be fully inserted into the plastic sleeve whenever the plug is in use Isolation input 6 pin DIN socket DIN pin EEG function ECG function Wire colour Left leg Input ve Left arm Buffer input iso power 2 4 Common 6 Common Common Shell Notes Buffer
19. E NECESSARY TO CORRECT THE INTERFERENCE Serial No Manufactured by CED Limited Cambridge England I I f CE amp WEEE symbols 16 position RS232 channel port set Power inlet Serial number position Rear panel features 19 Software supplied with the 1902 Try1902 Note 1902 ASCII commands The Stand alone 20 Control Panel Port Input Gain Offset Application software The 1902 is supplied with Try1902 a test and calibration program which is referred to throughout this manual Also supplied is Ctl1902 a stand alone applet for users who wish to run the 1902 as a simple electronic box In effect it supplies the knobs and switches of a logical front panel A similar applet is invoked by CED s principal software packages Spike2 and Signal to provide full operational control of the 1902 More details of Try1902 are given in the Help sections and in Maintenance amp Calibration Whatever the application all communication with the 1902 is ultimately in the form of short ASCII strings A full description of these is provided in the 1902 Technical Manual Open the Control Panel by selecting Start Programs 1902 Support Ctl1902 A window opens holding the 1902 controls These comprise dropdown lists and check boxes The contents and ranges on offer depend on the 1902 Ctl1902 interrogates the 1902 to see which options to display For example the notch filter check box will dis
20. EE RES 32 Basic mode of OPETALION sine sice tevers ictwtovinucaadonecnsueiteetsenedldeotes 33 Multiple independent channels ccccesssceceeseeeeeenteceeeeneees 34 Multi channel configurations and the1902 input buffer 35 1902 input clamp ODUOM ses dete esceucs cis oiel Heosreucs weet ees anwees 40 Use f th notch INCI a 1 5 ca coscedteesti nace mioetaatoraneduanateenevasdtaats 42 Theory of electrical 180 a0 Ot ves cecil esses vssetesinecce eet ons 43 eat the T902 naiaiae eae i e e eS 45 U Upd tin HMWAT Eae rne ana reen a EErEE ATE SARE 45 Calibration Losse orien et e eE a Sunde E a EEE a tens 45 Openingthe OO Dass a ae e A EEEE EA A 46 Try1902 the calibration utility 0 cc eceeceeseeceestteceesteeeeees 47 COnita Ci OED E E E E A 48 Servicine th 1902 rroetan a e R aE 49 THE 1902 motherboard sinoni nrraa aaa 50 Features of the motherboard ssesessesssessseesseesserssersssrsssesses 51 Circuit dia TANTS eneret re dy Ea EA E E SEE aat 51 Exchanging 1902 daughterboards 0 0 0 eeeecceceeseeceesteeeeeeeeees 52 Updating the EEPROM ss sesssssssssseseessesssssersseserssrsresseesesserseese 53 The EEG daughterboard isstecc tsar nena aatieisaiscaaledtedegeededvine 54 The Te Ga Sater O ge Ss sasasecsaiesexaesetaassnadesassessnones anvedessesares 55 The filter daughterboard ors ican cos fee una tonddna wohastenuadavsByseiadecshencdeds gt 56 EATS CD RAA x Seok creas obatbieracate E dadeesuaneetatrcne 57 User notis
21. IV this memory is an area of the flash ROM Earlier models used a small EEPROM The operating system the 1902 monitor is run directly from flash ROM The flash ROM also stores the data needed to boot up the microprocessor and configure the FPGA As a component of the 1902 processing core flash ROM data is part of the physical design and subject to revision and upgrade Updating the firmware is done through an option of Try1902 see page 45 As and when it becomes desirable to do so upgrade files will be offered as free downloads from CED s website www ced co uk Your current firmware version is displayed as the monitor version in the Try1902 window The hardware Isolated electrode input Trigger inputs 4 Electrodes Trigger 2 ETAN Trigger 1 mAN Transducer input Trigger Amplifier output output Transducer Trigger Out eo eer p RO f f Overload Power Power Trigger gate above Trigger signal below indicators indicator Front panel features 1902 mk v 5c i RS232 Serial line input DC Power In 15 Volt and 5 Volt Use ONLY power consumption CED approved A 4 Watts power supplies THIS EQUIPMENT COMPLIES WITH THE REQUIREMENTS IN PART 15 OF THE FCC RULES FOR A CLASS A COMPUTING DEVICE OPERATION OF THIS EQUIPMENT IN A RESIDENTIAL AREA MAY CAUSE UNACCEPTABLE INTERFERENCE TO RADIO AND TV RECEPTION REQUIRING THE OPERATOR TO TAKE WHATEVER STEPS AR
22. The CED 1902 Mk IV Owners Handbook Copyright Cambridge Electronic Design Limited 2012 Neither the whole nor any part of the information contained in or the product described in this guide may be adapted or reproduced in any material form except with the prior written approval of Cambridge Electronic Design Limited 1 edition 1 0 October 1991 2 edition 1 5 February 1992 3 edition 2 0 March 1997 4 edition 2 1 September 1997 5 edition 3 0 May 2006 6 edition 3 1 May 2008 7 edition 3 2 July 2012 Published by Cambridge Electronic Design Limited Science Park Milton Road Cambridge CB4 OFE UK Telephone 44 0 1223 420186 USA amp Canada Toll Free 1 800 345 7794 Fax 44 0 1223 420488 Web www ced co uk Email info ced co uk Trademarks and Tradenames used in this guide are acknowledged to be the Trademarks and Tradenames of their respective Companies and Corporations Preface Installation General information The hardware Application software Table of Contents Publishing infOnmatlOny c cicieccacdseevvsererodennecnetdetencsinteseeenaeetneaenl i Table Gl Contents asen a ii BALE SUP POR ENEE EEEE E EN Mulan tlet i Seadettiee iv Potential for Radio Television Interference USA only iv Storage and operating environment sessssssseesessseessrresssressees v Protection ntoro iee aoe a Satan natu E E v Typographic CONVeNtIONS ccccccceeseceesteceeseeeeeceeaeece
23. Trigger test prompt Pressing Trigger test opens a small window that invites you to test the trigger inputs with a signal generator and oscilloscope However just toggling the two radio buttons will change which of the yellow Gate LEDs is lit on the front panel EEPROM test checks the validity of data in a part of the flash ROM that is equivalent to the EEPROM of earlier 1902s This stores information that is specific to the 1902 in question such as its serial number and daughterboard configuration The test takes a few seconds and reports either success or failure If you are familiar with the 1902 command set documented in the 1902 Technical Manual you can send command strings to the 1902 by selecting Interactive mode Vary parameters allows you to set the high and low pass filters the notch filter and AC coupling as well as input mode gain and offset Calibrate amplifiers opens the calibration procedure this is dealt with below see page 45 General information Machine control In equipment used in research and industry it is highly desirable that all functions of instrumentation are readable and controllable by computer The 1902 achieves this by one of the most universal means the RS232 serial line or else an RS232 virtual port implemented on a USB adaptor Electrical When recording electrophysiological signals from live human isolation subjects it is a legal and ethical necessity to protect them from electric shock
24. Try1902 Once your 1902 is recognized look for the monitor version number displayed along with the port settings and the serial number Having downloaded a firmware update file with a f1li extension select File Update firmware from inside Try1902 The process is then almost completely automatic Repeat for each channel of 1902 Calibration should be performed every six months to retain the specified offset accuracy but if small discrepancies can be tolerated the interval may be extended to three years Bear in mind that calibration is a complex and time consuming procedure and should only be undertaken by an experienced technician To make the task as easy as possible the calibration option of Try1902 provides step by step instructions with graphic prompts for each The test sequence adapts itself to the particular configuration of the 1902 it finds Even so there are thirty six stages to be gone through in a unit with an isolation amplifier In view of the complexity of the task we strongly recommend that users return their 1902s to CED for calibration 45 46 Calibration tools required Opening the 1902 rN Inside the 1902 You will need e A digital voltmeter capable of resolving to 1 microvolt with a cable to mate with the internal test connector a Radiall SMB snap on socket see page 50 A dual channel oscilloscope with bandwidth of at least 10 MHz and sensitivity of 5 mV per division to attach to
25. ains frequency select 51 mains notch 12 25 46 response Bessel 10 21 56 Butterworth 10 21 Chebyshev 56 Firmware upgrades 18 45 Firmware version 18 Fixings combo screws 46 order of 46 52 rear panel screws 46 star washers 52 58 Flammable anaesthetic mixtures NOT v Flash ROM 18 50 fli files 45 Floating circuit 43 44 Fluff 45 FPGA 50 FPGA image 18 Front panel diagram 19 Front panel connections 16 G Gain accuracy 26 Gain range 25 26 Graphic symbols vi H Half bridge transducers 28 Hardware help desk 48 Hysteresis trigger input 29 I IEC 601 1 v 7 17 32 IEC cable 16 IEC Type B vi Impedance mismatch 36 Inner can 13 32 Input isolation amplifier 9 medical isolation 26 overload 40 transducer 28 transducer 9 trigger 29 40 waveform 12 Input buffer 35 37 54 Input capacitance 35 37 Input clamp 26 40 54 Input impedance 35 main amplifier 25 transducers 28 trigger 29 Input lead switching 55 Input offset drift 26 Input phase shift 35 Input selections clamped 41 isolated 41 non isolated 41 Input voltage trigger 29 Inputs balanced 35 Installation kit 1 Interference radio TV iv 13 16 31 Isolated clamped input 9 Isolated EEG or ECG amp c input 9 Isolation gap 43 Isolation leakage 26 Isolation voltage 26 Isometric transducers 28 L Laptop PCs 31 LED Gate 29 LED Power 5 LED Trig 29 LEDs Overload
26. at the first 1902 channel specified and continues until a missing 1902 is detected after the channel specified in this field So if there is a gap in your 1902 channel numbers you can use this field to force the search to cross the gap by setting it to your highest 1902 channel number Normally 1902 channel numbers are contiguous and you would leave this field set to Last found Once the settings are correct hit OK to save them to the Windows registry Once this is done all software using the 1902 either within a CED application or as stand alone support will be able to find and use your 1902s If you change the com port or the 1902 channel numbers you should use this Try1902 dialog to adjust your settings to match the new arrangements 15 Cable connections Power Earth OV 5 45 Key 15 ee 1902 power cable socket 16 RS232 A Signal cables A The hardware The 1902 needs both power and RS232 cables to be connected it will not function usefully without RS232 control although once the 1902 has been set up and is working properly the RS232 cable can be removed The two cables are applied to connectors on the rear panel The connector from the power supply is a Molex style cable socket at 0 156 pitch with a retaining ramp There are six pin positions one of which is blanked to provide a polarizing key This socket engages with the connector marked Power In If the CED power supply is being used this must be
27. atibility by the application of the following EMC standards Conducted and radiated emissions EN55022 1987 Class B COMPLIES Vfg1046 1984 COMPLIES FCC CFR47 Part 15 Subpart J Class A COMPLIES EN50082 1 1991 Immunity standards EN50082 1 Generic immunity PASS EIC801 2 Electrostatic discharge PASS 8kV Criterion A EIC801 3 RF field immunity PASS 3V m Criterion B EIC801 4 Electrical fast transients PASS 2kV Heavy industrial Criterion A Peter Rice Signature s pott Technical Director Date 20 July 2009
28. blem by doing one or more of the following e Re orient the receiving antenna e Re orient the position of the 1902 with respect to the receiver e Move the 1902 away from the receiver e Plug the 1902 into a different outlet so that the 1902 and the receiver are on different branch circuits If necessary consult CED or an experienced radio television technician for additional suggestions You may find the booklet prepared by the Federal Communications Commission helpful How to Identify and resolve Radio TV Interference Problems This is available from the US Government Printing Office Washington DC 20402 Stock no 004 000 00345 4 To comply with FCC rules Part 15 J Class B Computing device use only shielded interface cables Storage and operating environment pa Protection A Electrode Common leads Anaesthetic gases Preface The storage and operating environment for a 1902 must not exceed the temperature range 0 to 50 Celsius in conditions of non condensing humidity which should not exceed 95 saturation in an atmospheric pressure range of 500 hPa to 1060 hPa The 1902 complies with relevant EU and USA requirements for electromagnetic interference The 1902 is suitable for continuous operation The 1902 is not protected against ingress of water or dust There are no hazardous voltages inside the 1902 The 1902 can be recycled please contact CED for further details The 1902 offers Class I protection agains
29. devices There are passive SMT components mounted on both sides of the board The CPU can drive an ADC DAC pair in order to implement a digital filter So far as the analogue circuitry is concerned it is the same as the 1902 Mk III Jumper for mains notch 4 way switch pack filter Calibration SMB socket CED 1902 20 D the 1902 motherboard 50 Features of the motherboard The options switchpack The notch filter link Circuit diagrams Inside the 1902 The various adjustable pots and the Radiall SMB calibration connector are described in the calibration procedure see page 45 onwards Apart from that there are only two features on 1902 circuit boards that may be relevant to users The switch labelled OPTO on the 4 way switchpack is the most significant bit of the 1902 channel number When this is off the most
30. e 16 31 BNC 25 29 46 Socket drawings 27 Software help desk 48 Software installation 5 Somatosensory stimulus 40 Specification isolated input 26 main amplifier 25 Stand alone control panel 20 Start Menu 5 20 Strain gauges 28 Surface mount technology 50 Switches for trigger 30 T Temperature coefficient input offset 26 Test calibrate amplifiers 46 communications 5 EEPROM 6 others 6 trigger 6 Tools 1 pt cross head screwdriver 46 3mm flat screwdriver 14 insulated trimming tool 46 plastic pry tool 52 pliers 52 Transducer input differential 9 single ended 9 Transducers 28 Transformer 43 Trigger high level pulses 12 switch closure 12 Try1902 5 20 calibration 45 confidence check 5 monitor version 45 saving EEPROM data 53 setting port amp channel number 14 updating EEPROM 53 updating firmware 18 TTL input if source can t drive 29 TTL output 10 12 29 Typographic conventions vi U USB adaptor 5 13 31 Vv Voltage gain ECG 55 EEG 54 Voltage offset 12 W Water ingress of v Windows registry 14 15 Wire colours 27 59 60 User notes EC Declaration of Conformity This is to certify that the CED 1902 Manufactured by Cambridge Electronic Design Limited Science Park Milton Road Cambridge CB4 OFE UK Tel 44 01223 420186 Conforms with the protection requirements of Council Directive 2004 108 EC relating to Electromagnetic Comp
31. e the amplified signal with and without the notch filter in circuit and then make adjustments to the electrode cable routing positioning of the subject relative to overhead lighting etc The aim would be to minimize the waveform differences with and without the notch filter in place Note also that interference from sources such as fluorescent lights can be rich in harmonics of the mains frequency and a notch filter will only remove the fundamental component This can leave components at 150 Hz 250 Hz etc and hence the need for reduction of interference coupling at source by making improvements to the cable routing and the positioning of the subject Theory of electrical isolation Current flows in circles You cannot rely on insulation Floating power supplies Details of operation To be safe for use on live human subjects the electrodes and the circuitry connected to them have to be isolated To understand why first consider what actually happens when one receives an electric shock from the mains This illustration uses UK earthed neutral mains which can be quite lethal For our purposes AC can be regarded as slowly changing DC You usually receive a shock by touching a live point while grounded whereupon an electric current flows through your body to earth You may not be interested in what happens to it after that but it is relevant At the local substation transformer the neutral terminal of the secondary wind
32. e timed inputs will arm the clamp circuit which will then clamp the inputs for the selected length of time on receiving a trigger The clamp circuit begins to operate within a few tens of microseconds of receiving a trigger and the amplifier is fully clamped after about 200 microseconds The circuit can best deal with large potentials on the electrode inputs if they do not arrive before this time The implication is that if possible the clamp circuit should be triggered marginally before the stimulator One way of achieving this is to use external positive trigger pulses about 0 5 to 1 0 milliseconds in duration trigger the 1902 from the front rising edge and trigger the stimulator from the trailing falling edge The 1902 clamp time selected should be 0 5 to 1 0 milliseconds longer to compensate 41 42 Use of the Details of operation Trigger2 input Isolated electrode input CED 1902 Electrodes Analogue output Analogue output to 1401 Stimulus output Stimulator Clamping before stimulus The 1902 incorporates a mains frequency notch filter set at notch filter time of manufacture to be either 50 Hz or 60 Hz depending on Mains harmonics the country of destination It is important to note that a notch filter is a diagnostic tool for use during the set up phase of laboratory work and is not intended for use during the main recording If you suspect mains hum is corrupting your signals you should compar
33. eeeeeeeenes vi Use Of symbols ene a E Mas E vi INILOCUCHONS eae e e o e E 1 SOK ISD erenn treats rieesiun shania a care ahabatreecsees 1 The Electrode BOX i ccsicnsuciasssiocanidoancssunnsastunaecstantararnieexereeasetude 2 TheActive Head Stagen cren ae a EE EE 3 Installing the 1902 software ooenseeesseeseeeessesssseresssersssreessee 5 Confidence check Try1902 iain secscticctcoctesttaautese ieee unentatestss 5 Machine Control asena aa a A R 7 Electrical isolation ees rrrainis atier e Eea e 7 REL APO VAIS om vecsautericanuinedsantoutetvtntuldeaele AR A iA 7 Satety Approval Sase eeni ae pE EeP AAS EESTE Enik 7 Signal input to the 1902 ssnneeessessssseesssersssresssersssreessrrsssseessees 8 1902 functional organization ccecceeeesceceesteceesteceeeeteeeesenees 10 The waveform conditioner seeeseesesseseesseesserssssrrsseres 10 The trigger generator esssseesseseesseesseeresssresserssssresssres 10 Features seen by the user curt sscosscavcerericcebaccdl imeheaarncetsantenseens 12 Physical consttr ctioNssinieirn e sieaathaacs pieeaaies 13 Installations with multiple 19028 eee eeeesceeeeereeees 13 Rack mount installations eccceessceeseteceeeteeeeeeneeees 13 Using a USB pott csc ccuteevlaaves ana stcuterdeaad Medusuanal tenes taetalees 13 Channel numbers and how to set them ceeeeceeeeseeeeeeeees 14 1902 communication configuration ccessceeesteeeeeeeee
34. eeenees 14 CADIS COUME CT OMS 16555 xesuhgi shen E sete acess caw T AE REE 16 POWE aeoo Peay ane Re ae ar ee a et ean ee E 16 RS2 2 ae adds Bhaiste a satateen E EE 16 DIMA CADIES sor cetessnscctasctust evel acs e a EE 16 Electrod cables senen nene haan ieee a a e 17 Mating connectors ssesessseessesessseessssrssssresseresssrrsseresssreesereeso 17 Firmware the 1902 flash ROM csscccssessscoseescssssccseeees 18 Software supplied with the 1902 0 eesceesseceeesteeeeesneeees 20 The Stand alone Control Panel 0 ceecceceeseeceesteceeeeeeeeeenees 20 The control panel with CED applications ccceeessseeeeees 22 Electrical Specification Details of operation Inside the 1902 Index EC Declaration of Conformity Table of Contents Running the 1902 from Spike2 cccccccssceessceeeeeeeeeenteeeeeeeeees 23 Running the 1902 from Signal soeeessessseseessesesssersseresssressereesse 24 Main am pliiier oeenn Rian 25 Isolation Pre aMPlIehstaciarcwuw ent benrmaanadce wenGucatios 26 Isol ted INP UL jcsdetsctots tactic vata a a OEE 27 Transducer 1 DUE sais cteaus ecient A awa Seahawk aise 28 Bridge AFANSCUCETS x coicenssacssiasnutesesndacoanaviolaannesuueauncs 28 Sing le ended transducers c cc ethan teacnevscneetev en weeneuastt weet 28 Trigger CITC UIL cacveccesrieles e ea teen nleeee niente 29 Wiring Switches geseran a an ia 30 RS232 cable anian e E EEE EEE S 31 Pwer supply srece aE E
35. en a dco A E A 60 EC Declaration of Conformity ssesseseeseseeeessesesseresssressereesse 61 Life support Potential for Radio Television Interference USA only Preface CED products are not authorized for use as critical components in life support systems without the express written approval of the chairman of the board of directors of CED Life support systems in this context are systems which support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided can be reasonably expected to result in a significant injury to the user A critical component in this context is any component of a life support system whose failure to perform can reasonably be expected to cause the failure of the life support system or to affect its safety or effectiveness The 1902 generates and uses radio frequency energy and may cause interference to radio and television reception Your 1902 complies with the Specification in Subpart J of Part 15 of the Federal Communications Commission rules for a Class B computing device These specifications provide reasonable protection against such interference in a residential installation However there is no guarantee that interference will not occur in a particular installation If the 1902 does cause interference to radio or television reception which can be determined by turning the 1902 off and on you can try to eliminate the interference pro
36. h the power supply and DC cable to the 1902 can and case and all connector bodies apart from the isolation amplifier The Cable screen pin of the isolation connector is AC coupled to mains earth through a 1 nF 6 kV working capacitor The 1902 power supply must be plugged into a mains socket with a good earth For applications that do not need EN 60601 1 isolation the 1902 can be powered from another suitable source of stable power Any such power supply must have a mains earth through connection The 1902 requires approximately 220 mA at 5 V 75 mA at 15 V and 20 mA at 15 V plus whatever current is required for external transducers see page 28 Basic mode of operation Bipolar input Details of operation The simplest method of acquiring an electrophysiological signal with a 1902 is the Isolated EEG mode of Spike2 using a bipolar electrode configuration This involves three wires two as a differential signal input and a common lead to provide a return path for the tiny input bias currents NONE OF THESE LEADS must ever be connected to mains earth Note that for skin surface recording the electrodes are always connected to the isolated input The transducer input must not be used with human subjects The two signal leads form a differential input The signal that is detected and amplified is the algebraic difference between the voltages on the two electrodes This is achieved by inverting the ve input and su
37. ic Design Lig Cambridge Engi land 2 channel model shown Buffer option The Active Head Stage Installation The B option on the 2 and 4 channel boxes adds an input and output connector for the 1902 buffer option and also a rotary switch for selecting common reference buffer output drives all the ve inputs or bipolar buffer not used modes of operation Note that the buffer connectors are inoperative unless the correct output lead usually channel 0 is connected to a CED 1902 fitted with the buffer option For details of common reference operation using a buffer see page 35 The 16 channel boxes are available with either 16 signal electrode inputs plus common reference or 16 electrode pairs plus 4 buffer connections The CED1902 10 Active Head Stage is an optional electrode adaptor box similar to the CED 1902 11 mentioned above with safety plug connections for up to four electrodes It contains either two or four channels of battery powered differ ential amplifiers with N switchable gains of x1 x3 and x10 The outputs are AC coupled with a corner frequency of 1 6 Hz The Active Head Stage links together the Common leads of all electrodes connected to it The 1902 clamp option see page 40 cannot be used if this adaptor is present because its amplifiers are upstream of the clamp circuitry If clamping is required the CED 2804 External Clamp The 1902 Active Head Stage Box should be considered instead
38. ically off its connector pins It is important that these pins are not bent Install the replacement board in place of the original Take care to align the bottom entry connector sockets correctly with the connector pins on the motherboard Be patient Push the board down until it locates firmly on the shoulders of the nylon stand offs If any of the stand offs have come away with the old board push them out and re fit them in the motherboard The larger diameter end fits into the motherboard Reassembly is the reverse of disassembly Take care to replace the star washers correctly they form part of the IEC601 1 1 approval The screws holding the inner case lid have star washers between the screw heads and the lid these are specials that cannot be separated the earth bonding strap has a star washer between the ring tag and the case not under the screw head the rear panel has star washers under the screw heads Updating the EEPROM 1902 EEPROM setup Data from file Standard 192 Inside the 1902 If any change has been made to the daughterboards apart from swapping a faulty unit for one that is identical the EEPROM will have to be updated You will have been sent a file with a 192 extension with the correct information To reprogram the EEPROM start the Try1902 program select File EEPROM Setup and press the Load from disk button Browse to wherever you have saved the 192 file select it and press the Program 1902 button
39. ich accepts standard 1 5mm optionally 2mm safety plugs and connects to the 1902s via a 6 pin DIN plugs Alternatively users may wire the 6 pin DIN plug supplied with the 1902 to their own requirements A full kit of mating front panel connectors is supplied with the 1902 as are the serial line control cable and the power supply mains cable The standard connector kit comprises e One 8 pin DIN plug for transducers e One 4 pin mini DIN plug for the trigger e One 6 pin DIN plug for electrode signals Further connectors can be obtained from a variety of suppliers but for reference we have obtained ours here Part number Supplier UK tel No Trigger 4 pin mini DIN 152 208 08701 200200 e To meet the requirements of EN60601 1 only the DIN parts specified apart from trivial details of colour etc can be used for the electrode connectors e Ifthe DIN 6 pin connector is used the plastic cover must be kept fully pushed onto the plug body at all times 17 Firmware the 1902 flash ROM Other firmware Firmware upgrades 18 amp the Internet The hardware Because the 1902 has so many user specified options e g choice of front end high pass and low pass filter values notch filter frequency an internal read only memory is provided to hold the characteristics of the options fitted and suitable names in English for these options This simplifies the task of any controlling software In the 1902 Mk
40. id to the base clamping the Inside the 1902 circuit board These screws have built in shakeproof washers combo screws Undo the screws and lift off the lid 7 Replace the RS232 and the power cables and apply power You are now ready to run the calibration software Try1902 the Run the program Try1902 see page 5 Click the button calibration utility marked Calibrate amplifiers Full instructions appear on the screen Items to be adjusted or connected to will flash With up to twenty pots to adjust this is a great help You may step back as well as forward Stage 1 of 36 Stage 9 of 36 Lt Stage 22 of 36 Stage 36 of 36 Front end oe i U o O Calibrating the 1902 47 Contacting CED Info to have ready 48 Inside the 1902 CED operates both hardware and software help desks These are staffed by the same engineers and programmers who design CED s equipment and write the software If you need to phone either help desk but particularly hardware help it will be of great assistance to us if you could have the following information to hand e The model and serial number of your 1902 s the serial number is printed on the rear panel e The 1902 Monitor revision number from Try1902 e Details of the isolation daughterboard if present also from Try1902 e The version numbers of any CED application programs you are running from Help About Servicing the 1902 Sending it
41. ighly susceptible to noise pickup The input will not somehow default to a single ended configuration To maximize AC common mode rejection phase shift must be minimized That is to say the input time constant C R must be minimized see diagram on page 35 Minimizing and balancing the time constant by eliminating shared inputs has been discussed above Input capacitance can also be minimized using the Active Head Stage 1902 10 2 and 1902 10 4 see page 3 This is particularly useful if you are using mixed electrode types the capacitance of an Ag AgCl surface contact electrode will be quite different from that of a skin penetrating needle electrode The Active Head Stage minimizes capacitance differences very simply by reducing electrode lead lengths thereby reducing their capacitance The 1902 10 is a battery powered local amplifier with low impedance outputs which can satisfactorily drive signals down long leads to the 1902 Being identical to each other these leads introduce no phase shift In order to be effective the Active Head Stage has to be close to the subject Be careful not the let the box touch the subject since this will increase noise pickup The box should be positioned out of the way e g on the back of a headrest The 1902 10 is internally shielded with a coat of conductive paint It MUST NOT BE EARTHED since this will compromise the 1902 s isolation 39 1902 input clamp option When is the clamp needed
42. ings is robustly strapped to earth As much charge will flow out of earth as has flowed in through the victim This happens because were it not to a static voltage would rapidly build up and oppose further current flow So the current has to complete a circuit If no circuit can be completed no current can flow If you stand on a dry plastic bucket and touch one live point you will merely gain a static charge to mains voltage In the case of a person attached to mains powered equipment relying on insulation is completely impractical there is usually more than one wire connected to the subject not to mention intentional or accidental contacts with other equipment and earthed conductors including other persons There are too many possible paths for current flow The solution is to shrink the entire power supply circuit until it is contained within the 1902 and not connect it to earth at all This is known as a floating supply In the 1902 a miniature transformer provides power for the isolated circuitry signals to and from the rest of the 1902 pass through optoisolators There is an isolation gap of 6 mm between copper tracks on the two sides Insulation between the two sides is guaranteed to withstand mains voltages This greatly reduces the scope for current flow paths Charge cannot flow out of the electrode circuit so long as there is no way for it to come back it can only travel round the electrode wires The isolation socket has
43. inputs non isolated not for human subjects Optional isolated EEG electrode input Optional input clamping with EEG input Optional isolated ECG 5 lead input selection Gains from x100 to x100 000 in steps of x1 x3 x10 Optional gains from x1 000 to x1 000 000 in steps of x1 x3 x10 build option AC DC coupling switch 12 bit DC voltage offset Selectable mains frequency notch filter 50 Hz or 60 Hz Overload indicators readable by computer Trigger input converts from high level pulses or switch closures to TTL with program selectable choice of 2 inputs non isolated Digital filter with a wide range of user selectable settings Optional precision unity gain buffer for use in multi electrode configurations Physical construction Installations with multiple 1902s Rack mount installations Using a USB port Com port number The hardware The 1902 is built on a multilayer printed circuit motherboard to which a daughterboard may be attached to provide one of the various isolation options This is contained in a two part folded steel inner can that provides electromagnetic containment This assembly is mounted in the outer case also of folded steel that provides mechanical protection It is often the case that 1902s are purchased as multiple units Usually these will be dual or quad 1902s they are accommodated with external cases bolted together as a stack inside which the separate inner cans are mounted Mult
44. iple units are powered from a single power supply and cable and are driven from a single RS232 port in multi drop mode Typically the bottom unit will be the master to which the cables are attached Usually this will be set to the highest channel number For more on channel numbers see below Rack mount installations can accommodate up to four 1902s in a traditional 19 inch rack The folded steel case is 2U 89mm high inside this the 1902s are mounted in their inner cans The power supply is internal to the case and there is also a cooling fan A rack mount case presents only one load to an RS232 port and may contain buffers to drive other racks of 1902s Computers especially laptops are increasingly being supplied without an RS232 port In this case the 1902 can be connected to one of the USB ports via a USB virtual com port This is a cable that plugs into a USB port with a 9 way RS232 plug at the other end The RS232 port is powered from the USB socket It connects with the RS232 cable supplied by CED a standard RS232 cable will not work This hardware is inexpensive and readily obtainable The USB virtual com port should be installed before the 1902 During installation it will be assigned a com number e g Com5 which can be found by looking in Control Panel Device Manager Ports This is the com port that should be set during 1902 installation see page 5 13 Channel numbers and how to set them
45. is for AC power only This symbol is used on the power supply to show that the outputs are DC only The CED 1902 is subject to the EU WEEE regulations and may be returned to CED Ltd for recycling Observe precautions against electrostatic discharge Attention consult accompanying documents Introduction Checklist The power block Cables Installation This section will guide you through the installation of your CED 1902 Mk IV isolated pre amplifier This involves loading the operating software and running an initial confidence check The installation kit for your 1902 comprises e One or more 1902s either free standing or rack mount e A power block with attached DC power cable e A power block mains cable suitable for your country e An RS232 cable to connect the 1902 to your computer e A kit of accessories including plugs to match the front panel connectors e An installation disk to allow you to install and check out your 1902 e CED Electrode or Head Stage Boxes optional e This owners manual The 1902 power block will run with no adjustment on any mains voltage from 100 V to 240 V 50 Hz 60 Hz drawing 1 3 A maximum It has no switch being controlled by plugging in and switching on at the mains socket The 1902 itself has no DC power switch For electrical isolation to be complete mains power must be disconnected from the power block Use only the cables supplied by CED They have the
46. l to the ve inputs of all the channels In this arrangement each channel produces a measurement of the potential difference between its own electrode and the shared reference electrode Each electrode sees the same input capacitance load Right leg or other common point A Right leg or other common point Multi channel with Multi channel with independent electrode pairs shared buffered reference The Common electrode If you are using either the CED1902 10 Active Head Stage or one of the CED1902 11 Electrode Boxes note that the Common inputs of all 1902s are connected together inside the box and brought to a single input socket 37 Advantages of using a buffer Drawbacks of using a buffer Buffer connections 38 Details of operation The table shows the calculated degradation of CMRR with input loading It can be seen that the buffer circuit has clear advantages in multi channel configurations CMRR 50Hz dB Number of inputs Without buffer With buffer There are several possible problems associated with the use of a buffer circuit 1 The buffer introduces additional noise The amplifier used in the 1902 buffer option is the same type as is used in the main inputs so the resulting noise voltage is not more than V2 times that of an unbuffered configuration 2 The buffer has to be exactly unity gain if the common mode rejection performance is to be maintained The standard circuit using an operational amp
47. lifier as a buffer falls short of unity gain by an amount proportional to the reciprocal of the open loop gain of the amplifier at the frequency being considered The 1902 uses a more sophisticated circuit that is adjusted to exactly unity gain at say 50 Hz 3 A buffer introduces some phase shift in the signal passing through it This can reduce the common mode rejection of the multiple channel system but the resulting performance is independent of the number of channels connected to the buffer output see table above For wiring the buffer in see the isolated input connector pinout table on page 27 CED Electrode Boxes CED1902 11 2B and CED1902 11 4B make the buffer input and outputs available as touch proof terminals The Active Head Stage Minimizing input capacitance Using the Active Head Stage Details of operation As mentioned above common mode rejection is a major element in noise reduction see page 35 This is because many forms of noise mains interference in particular are picked up equally by both leads Common mode rejection is essentially a DC phenomenon but will apply to AC signals provided there is no phase shift between the electrodes It is important to note there must be two electrodes The common electrode should not be confused with a grounded input The differential inputs are high impedance so if one terminal is left unconnected it will float at an indeterminate voltage This configuration is h
48. logue filters Bandwidth for gains over x3000 Bandwidth with digital filters Gain accuracy Digital filter response Filter slope low and high pass Low pass filter corner frequency High pass filter corner frequency Rectification Filter latency Mains notch cut 50 Hz or 60 Hz Overload indicator indicate when input is overrange Transducer input Input impedance Input bias current Range of gains available Common mode range CMRR DC to 50 kHz 3dB in DC mode 0 16 Hz to 50 kHz in AC mode 25 kHz 3dB DC to 10 kHz 3dB 2 Bessel or Butterworth 2 or 3 order 12 or 18 dB octave 1 Hz 10 kHz cont variable 0 01 Hz 1 kHz cont variable User selectable 0 35 ms approx 50 dB typical 2 yellow LEDs 1 for each polarity 1 GOhm 50 nA max x1 to x100 000 in steps of 1 3 10 10 V gt 100 dB 25 Electrical specification A daughterboard option provides the 1902 with a medical specification isolation pre amplifier and associated isolated power supply This amplifier can be DC blocked with a corner frequency of 0 16Hz Any resistive electrode balancing network is expected to be external to this unit Isolation pre amplifier 26 Input impedance Input bias current at 25 C Noise referred to input 1 Hz 10 kHz Common mode rejection at 50 Hz Common mode voltage range Input offset voltage initial adjusted Input offset voltage vs temperature Input offset voltage
49. metal shells and screening braid that are necessary to meet the requirements for control of electromagnetic inter ference Others may not do SO The power block Powerbox PMP55 shown The Electrode Box Installation The CED1902 11 family comprises optional electrode adaptor boxes that plug into the electrode input sockets of CED 1902 isolation amplifiers There are four variants of the smaller box e CED1902 11 2 2 channel bipolar e CED1902 11 2B 2 channel bipolar or common reference e CED1902 11 4 4 channel bipolar e CED1902 11 4B 4 channel bipolar or common reference CED also manufactures two 16 channel electrode boxes e CED1902 11 16 16 channel common reference e CED1902 11 16B 16 channel bipolar or common reference The electrode boxes have input connectors for up to 16 electrode pairs plus common electrodes The connectors can be either 1 5mm or 2mm safety touch proof types The boxes are passive i e they do not amplify the signals The outputs are connected apemon re to the electrode inputs of AS CED 1902 isolation amplifiers via shielded sag Ret Out cables The boxes have two D1902 11 4 or more Common input cirode adaptor connectors that are linked together and to the Common leads of all the output cables The interior of the box is coated with The 1902 Electrode Box electro conductive paint which is electrically connected to the screens of the output cables El Cambridge g hectrom
50. mming it with the ve input Consequently any voltage that is present on both inputs is cancelled out and not amplified This is known as common mode rejection it applies to AC as well as DC so long as there is no phase shift It is also limited to a comparatively small input range about 1 volt As an example if there are 0 500136 volts on the ve input and 0 500289 volts on the ve input 0 500136 0 500289 0 000153 The approximately half volt common mode signal disappears the difference remains and since the larger signal is on the inverting input the result is negative This is what will be amplified Note that in this configuration the electrodes are symmetrical neither signal electrode nor the voltage it re cords is privileged over the other All more advanced modes of operation are elaborations of this basic configur ation J Right leg or other common point Bipolar electrode configuration 33 Multiple independent channels Dual bipolar input The Common electrode 34 Details of operation The 1902 electrode inputs are inherently differential they will reject a signal that is common to both electrodes This section describes two or more independent differential inputs Later sections will discuss multiple electrode input where there is a common shared reference Consider the simplest recording using multiple input two independent bipolar channels Each channel will detec
51. mplifier operates either normally ie with differential inputs or with a clamp of varying duration The source and mode are selected by one drop down list in the 1902 controls xi Port fo x Input Normal diff x Gain fi a z Normal diff Trigger s 26 Inverted diff Filters High pass Grounded EEG EEG unclamped Input drop down list version with electrode clamping 1902 Control Panel See page 20 for how to open the Control Panel and for more about the other controls See page 40 for a description of input clamping Please note that the input source DEFAULTS TO THE TRANSDUCER If you wish to use EEG or ECG EMG etc input you must first SELECT ONE OF THE ISOLATED INPUTS mentioned above General information Input mode table The input modes are tabulated below For the pinout of the transducer and isolation amplifier sockets see pages 27 and 28 For more on the fundamentals of differential input see page 33 Note that when selecting isolated input EEG is taken to include ECG EMG etc Source Mode Effect Grounded Both amplifier inputs grounded Single ended Input ve to amplifier non inverting input inverting input grounded Normal diff Input ve to non inverting input Input ve to inverting input Inverted diff Input ve to inverting input Input ve to non inverting input Grounded EEG Both amplifier inputs grounded Isolated EEG Input ve to non inverting input
52. n its place For details of the digital filter see page 10 Index 1902 master 13 trigger generator 10 waveform conditioner 10 1902 circuit diagrams 51 1902 Support CDROM 5 192 files 53 A AC DC coupling 3 12 25 Active head stage 3 34 Adjustable pots 51 Amplifier saturation 40 Application software com usage 16 Signal 5 10 20 24 Spike2 5 10 20 23 version number 48 ASCII command strings 20 AT chassis 31 ATX chassis 31 B Bandwidth 25 26 Bias current 25 26 33 34 37 54 Boot loader 18 BS 5724 7 Buffered input advantages 38 drawbacks 38 C Cable standard RS232 31 BNC coax 16 power 5 16 RS232 5 16 31 transducer 16 trigger 16 Cables fraying 45 from CED 1 users own 16 Calibration 45 3 yearly 45 6 monthly 45 at CED 45 CED 1401 22 ADC 22 CED s address 49 61 CED s email address 49 CED s telephone numbers i CED s website 18 45 CEDCOND INI 14 Channel number chans 16 31 14 rotary switch 14 switchpack 14 51 top bit 51 Channel numbers 5 14 gaps in sequence 15 lowest amp highest 15 Clamp amplifier unclamping 41 before stimulus 41 duration 41 mode link 54 MOSFET switches 40 response time 41 trigger2 40 Cleaning 45 CMRR 26 35 36 38 54 Com port 5 14 Coml 5 Com5 13 Common electrode 34 37 Common lead v 33 Common mode rejection 33 Common mode voltage range 26 54 Connector diagram
53. nd filter type Bessel or Butterworth If this channel has analogue filters rather than digital the two dropdown lists have just four values each The choice of corner frequencies depends ultimately on the values of components fitted on the filter daughterboard One choice is always None or DC i e straight through The signal can be rectified i e all negative excursions of the signal are inverted This is mainly of interest during EMG studies As well as rectifying you can choose x10 gain This is a filter to attenuate mains pickup It is set during manufacture to either 50 Hz or 60 Hz the check box switches it in or out Note that this is provided for diagnostic purposes only it is not intended for use during experiments See page 42 AC coupling blocks the DC component of a signal It can be very useful for instance if your signal happens to be a small ripple on a large DC level It does attenuate very low frequencies the corner frequency is approximately 0 16 Hz Note that DC values of greater than 150 mV applied to the isolated electrode input may cause saturation in the input amplifier even with AC coupling selected 21 22 Trigger The control panel with CED applications Application software This toggles between the two trigger inputs which are functionally identical A check box can set triggering to occur on the falling edge In previous versions of the 1902 only the rising edge could be used
54. no connection to any mains conductors so it cannot act as a conduit for shock current from other equipment To keep it this way 1902 electrodes should NEVER be earthed 43 Limits of isolation 44 Details of operation It will be apparent from the foregoing that while one contact between a floating circuit and the rest of the world is safe two contacts are not because the possibility then exists of their forming a current loop that includes the subject An experimental set up can only be as safe as its least safe component the best that each piece of equipment can do is not to provide a conduit for shock current flowing through itself Cleaning the 1902 Updating firmware Calibration Calibration at CED Inside the 1902 The 1902 needs regular cleaning to remain in good condition Before cleaning remove power and all cables from the 1902 The exteriors of the 1902 case and the power supply should be cleaned annually to remove deposits of foreign matter with a soft cloth moistened with water Avoid spilling drops of water or any other liquid on the 1902 Check the sockets for pieces of paper or fluff If any are seen remove them with a pin Check the cables visually for fraying or other mechanical damage The 1902 Mk IV has user updatable firmware Updating the firmware is only necessary if the version available for free download from CED s website is later than your own To find which version you have open
55. oltage range operating 15 V no damage 50 V Input impedance 100 kOhm Trigger threshold for ve going input 1 5 V approx Lower trigger threshold 1 0 V approx Output pulse TTL negative going Output pulse length 3 us nominal Trigger output drive capability 0 8 mA maximum Pin Function Wire colour 1 Comparatorinpnt o o E ground 3 Internal pull up SVviadk7 4 intemal pull down OV via4K7 magere shon Mainsean o 4 pin mini DIN socket e A human subject must NOT be connected to this input socket 29 Electrical specification Wiring switches To use a switch that is normally open as a trigger source connect pins 1 and 4 to one contact and pin 3 to the other Connect the screen to the switch body Closing the switch raises the input from 0 V to 2 5 V To use a switch that is normally closed connect pin 1 to pin 3 the switch between pin 3 and pin 2 and the screen to the switch body Opening the switch raises the input from 0 V to 5 V Screen Screen 30 Wiring for normally open switch Wiring for normally closed switch RS232 port 1 5 aC 6 9 RS232 port 9 pin D plug RS232 to USB converters Electrical specification The RS232 port is a standard 9 pin D plug The functions DSR CD and RTS are connected together within the 1902 case so that a simple pin to pin cable can be used The RS232 serial line cable provided with the 1902 has a 9 way D type socket at each end
56. ote of which physical com port the RS232 goes into most likely Com1 many computers only have one com port Some computers especially laptops have no com port at all in this case use a USB RS232 adaptor see page 13 Switch 1902 power on at the mains Observe on the front panel that the green Power LED comes on Open Tryl1902 by selecting Start Programs 1902 Support Try1902 First of all you must set the com port and the 1902 channel dropdown lists These identify the com port being used and the channel number to which the 1902 is set As soon as they correspond to the 1902 present it will be identified and reported In multiple installations where all 1902s share the same com port the 1902 identified will change as the channel number is changed The numbers will correspond to the 1902 unit numbers 0 1 2 etc In single installations the channel number will be 0 unless specified otherwise This is the most basic test simply checking that the 1902 will accept and return data Press Communications test to start the test Stop testing stops the test and reports the number of passes repetitions done and errors found if any Installation Trigger test EEPROM test Other tests Untitled Try1902 stop testing Communications test started Communications test stopped 0 errors in 24 passes Interactive mode started Trigger test Interactive mode finished EEPROM checksum test OK Try1902 with
57. ould not exceed 10 mA Bridge transducers The differential input is connected to a force or pressure transducer or to a strain gauge The 1902 can provide the voltage excitation needed For half bridge types binding adaptors must be used to complete the bridge Single ended Single ended transducers should be connected between the ve transducers input pin 5 and ground pin 1 The ve input pin 7 should be linked to ground The 1902 voltage offset facility on pin 6 can be used to back off a static voltage level at the transducer output 28 Electrical specification Trigger circuit The trigger circuit accepts signals from high impedance sources that cannot drive TTL inputs such as sensors it can also be A wired to a switch Trigger connections are made to two mini DIN sockets on the front panel one of which will always be active as shown by its yellow Gate LED Each trigger input drives a comparator which responds to a positive going signal by default giving a flash on its yellow Trig LED In 1902 Mk IV the comparator may be set to trigger on a negative going signal The comparator has hysteresis it fires on a rising voltage at 1 5 V but does not relax until it has fallen back to 1 0 V This reduces repeated triggering from noisy signals The trigger circuit output is through a standard BNC socket The driver is a 74HCT04 inverter element this chip is in a socket for easy replacement in case of damage Trigger input v
58. play either 50 Hz or 60 Hz Here briefly are the controls This is the 1902 channel number For use with just one 1902 it is greyed out This selects waveform input from the transducer or the isolation amplifier It sets the various operating modes such as single ended or differential for the transducer or various clamp delays on the isolation amplifier This is the voltage gain of the input selected It may not go down to unity some inputs have minimum gains of 100x or 1000x Rather than use the dropdown list the spin controls to the right may be used This is a fixed DC voltage summed with the input to centre the signal about zero a positive or negative value in millivolts may be entered by keyboard or the spin controls can be used for steps of 5 Low pass amp high pass filters EMG processing Notch filter AC couple Application software 1902 controls x Port fo Input isolated EEG a hoo z Offset po 8 Gain 11000 ir WA 0 I Trigger 2 1 J Falling edge trigger Filters High pass Low pass 2 pole Bessel 7 2 pole B wWorth a Cutoff fas Hz aa Hz Cutoff 100 Hz 7 Hz T AC couple V 50 Hz Notch EMG processing Rectity amp 10 a Apply Cancel Help 1902 Stand alone Control Panel For digital filters the corner frequencies are selected from dropdown lists or users may type in their own values They can also select slope 2 pole or 3 pole a
59. smatch Shared electrodes 36 Details of operation The table shows the calculated degradation of CMRR with impedance mismatch Note how an initial small mismatch causes the steepest fall off in performance Impedance mismatch kOhm CMRR 50Hz dB 0 The diagram below shows the situation when two channels are used with a shared reference electrode The shared electrode now sees a load equal to twice the load seen by each of the unshared electrodes Its time constant may be expected to be approximately double that of the other two This is a configuration to avoid by one of the methods that follow Electrode 2 Electrode 3 shared Common Channels with shared reference electrode Independent electrode pairs Electrodes with shared reference Details of operation The diagram on the left shows a multi channel 1902 setup where each channel has separate ve and ve electrodes Each channel produces an independent measurement of the potential difference between the electrodes associated with that channel There is one common electrode providing the bias current return path This type of arrangement is appropriate for measurement of parameters such as EMG where individual muscle sites are being examined The diagram on the right shows the configuration with a buffer circuit in operation One electrode the reference electrode is taken to the buffer input and the output of the buffer is fed in paralle
60. suitable for AT and ATX chassis PCs The baud rate is fixed at 9600 Function Wire colour Signal ground DTR to 1902 Data to 1902 Data from 1902 KE E E a ee E DRA Jo peeo a gt o a a CTS from 1902 e For correct EMC performance it is essential that the serial line cable connectors have good quality metal shrouds and that they are clamped with integral jackscrews to the threaded posts provided on the 1902 and on the computer e The cable must be screened with metal braid or foil which should be clamped to the shrouds at both ends To use the 1902 with a computer such as a laptop that may not have a physical com port consider one of the commercially available devices that implement a virtual RS232 port on the end of a USB plug The special RS232 cable supplied by CED must still be used See page 13 for more on this 31 32 Power supply Mains electricity Mains earth Other power supplies Electrical specification The 1902 must be powered from a CED approved power supply if it is to meet the EN 60601 1 1 2000 safety and EN 60601 1 2 2001 EMC standards The Powerbox model PMP55 32 J12 is the current April 2008 approved supply This power supply accepts mains voltages from 100 V AC to 240 V AC at frequencies from 50 Hz to 60 Hz without needing adjustment by the user The 1902 power supply draws typically 30 VA There is electrical earth continuity from the mains plug and mains cable throug
61. t and amplify the Jocal voltage difference between its ve and ve electrodes Because each channel is independent any voltage difference between the two electrode pairs will not be amplified Additionally a sig nificant voltage gradient between widely spaced elect rode pairs will entail only insignificant voltage differences between the closely spaced electrodes of a single channel Right leg or other common point Dual channel bipolar configuration Because the isolated sides of separate 1902s are isolated from each other the Common inputs of all 1902 channels need to be tied together The Common input pin is connected to the zero volts point of the floating circuitry and serves as a return path for the very small bias currents of the electrode inputs If you are using either the CED1902 10 Active Head Stage or one of the CED1902 11 Electrode Boxes note that the Common inputs of all 1902s are connected together inside the box and brought to a single input socket Multi channel configurations and the1902 input buffer Why use a buffer Details of operation The input buffer option CED1902 4 B is used in multi channel configurations where a shared reference potential is required The option is completely housed inside one of the boxes usually channel 0 of a multi channel configuration It uses spare pins on the isolation input connector to take an input signal in buffer it and feed it back out The
62. t electric shock To maintain the safety standard accessory equipment attached to the 1902 must also comply with relevant safety requirements such as IEC601 1 or the relevant IEC standard e g EN60601 1 configured to comply with EN60601 1 1 2000 The Common lead on a three wire electrode cable provides a return path for the input amplifier bias currents UNDER NO CIRCUMSTANCES should this lead or any other electrode lead be connected to mains earth This will negate the 1902 s isolation provisions and expose subjects to the risk of fatal shock The 1902 is not protected against flammable anaesthetic mixtures It must NOT be used in the presence of such mixtures vi Typographic conventions Use of symbols gt pit Preface The following conventions apply to the text in this manual e Titles of manual sections other manuals and other publications are in italics e Labels and identifiers appearing on the equipment described in this manual are in Arial e Menu items buttons and other contents of computer displays are in Arial italics e Text entered by keyboard is in Courier New Names of keys are enclosed in angular brackets e g lt esc gt lt enter gt Where applied the symbols below have the following meanings This symbol is used on the CED approved power supply to denote that the electrical isolation is to IEC Type B standard This symbol is used on the power supply to indicate the mains input
63. trigger pulse to be routed to the clamp circuit Clamping waveforms Details of operation Selection of timing values Connection of external equipment Details of operation The timing unit can generate pulses in the range 0 5 to 14 milliseconds the length being determined by the input source selected by software On receipt of the selected edge on the Trigger 2 input the timing circuit generates a pulse of the selected length The 1902 Mk IV has the option of selecting to trigger on positive rising or negative falling edges of the trigger signal The timed pulse operates switches that disconnect the electrode inputs from the input amplifier During the length of the timing pulse the 1902 output will be undefined but will stay within its linear range At the end of the timing period the input is unclamped and the amplifier output will jump to a level representing the new value of the inputs In addition to the four transducer input selections Ground Normal differential Reverse differential and Single ended and the two isolated selections Grounded EEG and Unclamped EEG there are thirteen additional isolated input settings These are given times in milliseconds 0 5 ms 1 0 ms 1 5 ms 2 0 ms 3 ms 4 ms 5 ms 6 ms 7 ms 8 ms 10 ms 12 ms 14 ms Other multiples of these basic times are available to special order So far as the user is concerned these are normal EEG inputs However selecting one of thes
64. ughterboard overall 1902 voltage gain is software selectable between x1 000 and 1 000 000 or between x100 and x100 000 these build options being at the user s choice CED1902 04 C the EEG daughterboard Inside the 1902 The ECG The ECG daughterboard designated the CED1902 02 provides daughterboard medical isolation designed to meet EN60601 1 isolation standards It has input lead switching so the one connector can measure differential or resistively summed voltages between four electrodes nominally Left arm Right arm Left leg and Vagus Overall 1902 voltage gain is selectable between x100 and 100 000 CED1902 02 the ECG daughterboard 55 56 The filter daughterboard Inside the 1902 The analogue filter daughterboard is built to implement 2nd order filters with 12 dB per octave roll off The standard configuration is Butterworth optimised for flatness of response before the corner frequency Bessel or Chebyshev polynomials can also be supplied to special order The corner frequencies and the response are determined by the precise value of the resistors and capacitors fitted High frequency and low frequency sections each have four selectable positions including straight through The high pass filter comes before the low pass filter CED1902 03 the filter daughterboard If the digital filter has been implemented this daughterboard is omitted and the digital filter components are fitted i
65. user may then connect the buffer output to one terminal of several normal input channels without imposing additional load on the reference electrode The presence of the buffer option does not affect the normal operation of the channel that houses it To understand why a buffer amplifier may be necessary we need an explanation of the effects of input impedance practical considerations that receive scant attention in medical instrumentation literature The diagram shows a single bipolar channel using two electrodes plus common It shows the electrode skin junction as a pure voltage generator with series output resistance It shows the capacitance of the cable plus the input capacitance of the amplifier as a single lumped Channel with unshared electrodes com ponent It is important that the time constants the products of the series resistance and the combined capacitance at each input should balance Unbalanced time constants cause differential phase shifts in the input which lead to a reduction in the common mode rejection ratio CMRR Common mode rejection is particularly important for reducing pickup of mains frequency and its harmonics Electrodes Since the input capacitances tend to be similar and in any case are difficult to modify the emphasis is on ensuring that the electrode contact resistances are balanced the usual way to achieve this is to try to make them as close to zero as possible 35 Impedance mi
66. y the application itself see examples below usually renders the oscilloscope superfluous Application software Running the Spike2 is optimized for the analysis and recording of continuous 1902 from Spike2 data possibly on many channels Analysis of EEGs during sleep would be a typical task involving 1902s All controls remain accessible during data sampling but if offset and gain are altered the last settings are recorded as the offset and gain of the entire data The alterations are logged on a marker channel however so earlier data can be re scaled laid File Edit view Analysis Cursor Sample Script Window Help BSH BOS AMS w v it mE F aa _ Stop Abort Reset_ m wite x Port 0 7 Input ECG 5 Gain fioo zj Offset fo E Trigger C 2 1 Falling edge trigger Filters High pass Low pass 2 pole B worth z 2 pole B Worth Cutoff 0 1 z Hz Cutoff 100 Hz I AC couple T 50 He Notch EMG processing None zj Appl Cancel Help AP WAVE mmHG 289 5 290 0 290 5 291 0 291 5 292 0 292 5 293 0 293 5 294 0 294 5 295 0 295 5 296 0 296 5 297 0 297 5 298 0 298 5 299 0 299 5 g For Help press F1 295 344 O r oR Spike2 sampling ECG with 1902 control panel 23 Application software Running the Signal is optimized for the analysis of sweep based information 1902 from Signal where a sequence of data is recorded repetitively often synchronized to a repeated stimulus

1902 mkIV

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