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A Precision Low-Level DAS/ECG Cardiotachometer Demo Board

A Precision Low-Level DAS/ECG Cardiotachometer Demo Board. Created by Dr. John Brown Prepared by Thomas Kuehl & Laura Groskie Texas Instruments – Tucson, AZ. A Precision Low-Level DAS/ECG Cardiotachometer Demo Board. Presentation Outline. Biopotentials Electrocardiogram, ECG

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A Precision Low-Level DAS/ECG Cardiotachometer Demo Board

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  1. A Precision Low-Level DAS/ECGCardiotachometer Demo Board Created by Dr. John Brown Prepared by Thomas Kuehl & Laura Groskie Texas Instruments – Tucson, AZ

  2. A Precision Low-Level DAS/ECGCardiotachometer Demo Board Presentation Outline • Biopotentials • Electrocardiogram, ECG • ECG characteristics • ECG electrodes and connections • The DAS/ECG board electrical functions and capabilities • AC and DC applications for the DAS/ECG board

  3. Biopotentials – Muscle Cell Muscle Reaction Resting State

  4. Biopotentials from Cells Electrical Signals From the Body + + Na Na + + K K ++ ++ Ca Ca - - Cl Cl EVERY CELL IS LIKE A LITTLE BATTERY Action Potential Voltage Reversed Potential +20mV HUMAN CELL 0V Volts Time -70mV Repolarization Depolarization IONS Resting Potential -70mV

  5. Biopotentials from Cells Electrical Signals From the Heart

  6. Cardiac Conduction System of the HeartECG Waveforms English E C G, German E K G P, Q, R, S, T, U Left Heart Contracts Biggest Heart Muscle, R Wave

  7. IONS to ELECTRONS CONVERTER Electrodes Convert DIAGNOSTIC Ionic Signals From The Body MONITOR Into Electrical Signals in Wires ECG BP Muscle Machine TEMP RESP + Na - - - e e e + K - Cl Biopotentials from Cells - Electrodes

  8. ECG Elec +2.5V +2.5V Basic ECG electrode connections Electrocardiogram Records Electrical Changes From Beating Heart ECG is Measure of Heart as a Ionic or Electrical Generator Vin- INA (Left Arm) Vin = Vin+ - Vin- +2.5V dc +2.5V dc Vin+ INA Heart (Right Arm) Electrodes Transduce Ions Into Electrons +2.5V dc Common-mode Volt = (Vin+ + Vin-)/2 (Used for RL Drive)

  9. ECG Einthoven Triangle, 1907 3 Derived Leads I, II, III Einthoven’s Law In electrocardiogram at any given instant the potential of any wave in Lead 2 is equal to the sum of the potentials in Lead I and III. 3 Body Electrodes II = VLL-RL – VRA-RL III = VLL-RL – VLA-RL RL Ref I = VLA-RL – VRA-RL

  10. ECG Electrode – Electrical Model Electrode 0 to 500mV 0.5 to 10F Skin 0.5 to 100k 1k 1F Body 10k 55 10^10 10kΩ 1k 1F Frequency Response BSEA Ions to Electrons Fo = 1 / 2 π RC Fo = 0.159 / (1k) (1F) = 159Hz Amplifier

  11. ECG and Blood Pressure Waves 120 mm Hg Vessel Maximum Pressure Head Pressure signal has slower rise 30Hz BW, 25 harmonics ECG signal has faster rise 100Hz BW, 70 harmonics 60 mm Hg Vessel Relaxation R 1 mV p-p T P U S Q Left Heart Relaxes Left Heart Contracts

  12. Actual ECG - Normal 24 mm, 0.96 sec Chart Speed: 25mm / sec R 1mV Cal T U P Q 10 mm, 1 mVp-p S = BW 10 mm = 1 mV 10mm = 0.4sec BASELINE or dc DRIFT Charging Time Constant of High Pass Filter and Changing Electrode Half-Cell Potential 24 mm x 1 sec / 25mm = 0.96 sec / beat => 1 / 0.96 sec = 1.04 bps 62 bpm at rest

  13. ECG Irregular Tracings Due to Artifacts 60Hz Pick-Up Baseline dc Instability Muscle Shaking Baseline or dc Drift

  14. A Precision Low-Level DAS/ECGCardiotachometer Demo Board Can Also Be Used As Precision Low-Level Data Acquisition System Front-End Heart Rate Monitor Application of TI ICs “Mr. E. C. Gee” ECG Vin- INA Demo Board (Left Arm) Meter 6 0 0 BPM About 1mVp-p Heart Vin+ INA Single +5V Supply (Right Arm) Beeping Speaker Flashing LED VCM = (Vin+ + Vin-)/2 Common-mode volt Used for RL drive (Right Leg) John Brown, 12/5/2006

  15. A Precision Low-Level DAS/ECGCardiotachometer Demo Board BP ECG Vin- INA (Left Arm) Meter 6 0 0 Finger INA & OPAs Vout Cardiotach Circuit BPM 0.15 – 2.5mVp-p Heart Vin+ INA (Right Arm) Vout, Overall Non-Inv Gain With Respect to Vin- INA (Right Leg) Speaker LED Common-mode Volt = (Vin+ + Vin-)/2 (Used for RL Drive)

  16. A Precision Low-Level DAS/ECGCardiotachometer Demo Board Uses 7 TI IC Types, 11 U’s Total TPS71550 TLV3491 Resistor Divider for Creating Differential Voltages on Demo Board Auto Power Down Ckt LDO SubReg Ckt +5.2V to +24V dc +4.8V dc, <1mA to 15mA +5V Vin BP ECG 0.1uF U8 U7 RA 499k 0.1uF Cb7,8 Cb9 Vin- INA (Left Arm) 6 0 0 Meter Cardiotach Circuit Finger RB 499k Vout BPM Vdiff INA326 OPA335s 0.15 – 2.5mVp-p Heart OPA335s TLC556 Vin+ INA 0.1uF Cb1,2,3,4,5,6 (Right Arm) DIP-8 Socket OPT101 U1, U2, U3 U4, U5, U6 RC 499k Vout, Overall Non-Inv Gain With Respect to Vin- INA U11 +2.5V out OPA335 REF3025 U9 Speaker LED Common-mode Volt Uncommitted Op Amp = (Vin+ + Vin-)/2 U10 (Used for RL Drive)

  17. A Precision Low-Level DAS/ECGCardiotachometer Demo Board + - AC-coupled input stage LPF Normal-Mode dc Removed Normal-Mode dc R 480R 0.48V dc + 2mV p-p G = -480 GT = 2,400 - +5V G = 5 Vin- - OPA336, 335 4.9V max +5V +2.5V Offset Tiny Signal 1mVp in + INA326 4.8Vp-p max HPF +2.5V ±2.4Vp Vin+ + IA Ref Pin 0.1V min 0.48V dc + 1mV p-p +2.5V Offset +2.5V Input Vcm Integrator in Feedback Common = 0V, Vref = +2.5V

  18. A Precision Low-Level DAS/ECGCardiotachometer Demo Board 0.1uF Cb2 - - + + Right leg drive circuit 22pF R1 R4 C2 390k 1k Vin- (Left Arm) 480mV max dc differential electrode potential 2 C1 R6 100pF - Vin = Vin+ - Vin- 1 40.2k U1 INA326 +2.5V dc 0.15 - 2.4mVp-p 8 3 40.2k + R7 R2 Heart +2.5V dc R5 390k 1k Vin+ C3 RG =R6+R7 22pF (Right Arm) +5V 2 Vcm + 8 1 A1 4 3 U2 47pF C4 R8 OPA2335 Self-Zero R9 20k 390k +2.5V dc 6 7 390k A2 +2.5 R3 Common-mode Volt Vcm - 5 = (Vin+ + Vin-)/2 (Used for RL Drive) (high inverting gain) Right Leg Drive Amplifier

  19. A Precision Low-Level DAS/ECGCardiotachometer Demo Board 0.1uF 0.1uF + Cb3 Cb1 - - +5V + 8 C high pass = 1uF Integrator (high pass filter): Time Constant = RC. Fo= 0.05Hz diagnostic mode, 0.5Hz monitor mode, and 2Hz quick restore Power Supply Analog Circuit Common (isolated from earth ground) +Vs -Vs CMOS +5V SINGLE SUPPLY, INA326/7 & OPA2335 GT=1k,2k,4k,6k Stage2, Gain = 200 – 1,200 CLPFext xxxxuF xxxxHz Total Gain = 1,000 – 6,000 Low Pass Filters (noise roll off) C7 0.0015uF 100Hz Stage1, Gain = 5 C8 0.0047uF 35Hz V IA Out C9 0.01uF 17Hz Total Gain, V/V RGext 4.99k x1k R14 +5V Centered +2.5V U1 1M x2k R15 2.49k Vout 2 7 R18 1.24k x4k R16 1 INA326, 327 (shtdn) R/R I/O Self-Zero A3 x6k R17 0.825k = Vin x Rgain total 4 6 3 Vout INA 0.15V to 4.8Vp-p out High Pass Filters (dc restoration) ac Hold 4 5 R12 316k 0.5Hz R13 80.6k 2Hz (quick restore) R11 3.01M 0.05Hz C5 R10 470pF 200k 20k ac 5 +2.5V dc 7 +5V supply U3 Vdc pedestal ½ Vsup A4 R19 20k OPA2335 Self-Zero 6 C6 R20 Electrically Isolated from Earth Gnd +2.5V dc ac-CoupledRemoves dc electrode offset

  20. A Precision Low-Level DAS/ECGCardiotachometer Demo Board Av f-3dB = 1/(2πR2C2) f DC restorer - removes electrode offset Vout frequency response 0.05Hz

  21. A Precision Low-Level DAS/ECGCardiotachometer Demo Board BPM Light Flash Sound Burst 6 0 0 <30 to >240 Beats per Minute BPM Meter Differentiator Pulse Peak Pulse Stretcher Burst Output Front-End Meter Flasher Beep oscillator ECG (Electro) Or BP (Optical) Differentiator Peak-to-Peak Detector One Shot Multivibrator See Detailed Circuits

  22. A Precision Low-Level DAS/ECGCardiotachometer Demo Board ECG Elec +2.5V +2.5V 0.1uF 0.1uF 0.1uF Cb5 Cb4 Cb6 +5V Single Supply Front-End <30 to >240 Beats per Minute Differentiator & Pos-Neg Peak-to-Peak Detector Burst Output One Shot Pulse Stretcher fosc = 1.44 / C15 (R26 + 2R27)  1kHz +5V 0V 50% osc duty cycle +5V Person Common thi = 0.693 C15 (R26+R27), tlo = 0.693 C15 R26 TON = 1.1R25C13 = 0.1s Vout D2 0.01F 0.01F C10 6 IN4148 R26 R25 C14 C12 7 4 3 11 1M 28k 14 +5V 5 0.1F 2 8 9 D1 ½ TLC556 Dual Timer One-Shot 100msec ½ TLC556 Dual Timer Oscillator 1kHz R22 1 5 2M R27 13 1 R28 R29 C11 61.9k 3 4.99k 249 4 IN4148 0.1F 2 12 3.01M C16 R19 R20 8 R21 1F 20k 20k OPA2335 0.01F 0.1F U4 C15 C13 5 10 6 +5V Reset Trig R24 100k U6 +5V 7 R23 Clean Triggering 2 8 10k 6 1 7 3 +5V +5V OPA2335 4 U5 LED Speaker 5 0V 0V Vdcpedestal = +2.5V = ½ Vsup

  23. A Precision Low-Level DAS/ECGCardiotachometer Demo Board i e Battery, Power Sub-Regulator and Auto Power Down Circuit <1mA to 15mA On  6A Off Battery +6.5V to +9.25V +5.9V to +8.65V Reg Output Power Down When C3 is Charged >90% of Vreg 4A Iq 4 D3 0.6V Drop Ext. TPS 71550 5V LDO Reg Reverse bat protect External Supply +5.1V to +24V +5V Vreg +4.8V +5V +4.5V 5 10M 1.2A Iq 1A U8 Cb7 SOT323-5 SC70 R30 1M + C17 +1mA to +15mA 0A 0.1F 4 5 R31 - 9V Battery 2 Cb8 U7 R33 1 C18 TLV 3491 Comp sot23-5 1k 0.47F +4.5V dc - C19 + 100F Load 2 3 1M 4.75M C3 R32 R34 Common, Isolated or Ground 90% of 5V Threshold Mom. close SW to Start Timer 40 minutes to Auto Turn-Off

  24. A Precision Low-Level DAS/ECGCardiotachometer Demo Board • “Pin-Plug and Play” features • Wires to pin-sockets, no soldering, plus plug selectable gain & BW • Self contained ICs, resistors, capacitors, LED, speaker, switches • Battery operated (+9V included) or external supply up to 24V max with auto-sleep • Adjustable gain & BW (Separate LPF & HPF), differential or single-ended inputs, ac or dc coupled • Breadboard area for additional circuits

  25. A Precision Low-Level DAS/ECGCardiotachometer Demo Board – top side Left Thumb Right Thumb Right Finger Underneath Can Hold Right Side of Board Against Table to Steady Skin-Electrode Contact Speaker On G = 1kV/V 0.05Hz to 35Hz BW OPT Not Used In This Example Plugged Into ac-Coupled Position Forward, Out put Swing Up From Mid +2.5Vdc Towards +5V ac-coupled ECG Waveform Appear at Vout

  26. A Precision Low-Level DAS/ECGCardiotachometer Demo Board – top side Gain Control, Selected By Changing Shorting Bar Position LA Input LED 40 minute Timer Start Vsup Ext Gain x1k,2k,4k,6kExt Off/On Switch Input Pins Speaker Vout ac dc LPF 17,35,100HzExt +5V RA Input HPF dc,0.05,0.5,2Hz Com RL back

  27. A Precision Low-Level DAS/ECGCardiotachometer Demo Board – top side Digital Burst Out Test Point Independent Op Amp U9 with Pin Sockets Burst Oscillator U6 TLC556 ac Peak-to-Peak Detector U4, U5 4 Op Amps Start Timer Push Button Comparator U8 TLV3491 +2.5V REF3025 U10 with Test Point LED Left Arm Pad, Vin- of IA External Pwr Supply Input 8-pin DIP Socket U11 with Pin Sockets ½ Vsup test pt IA Out test pt Off/On Switch Vin+, Vin-, and Vin common-mode (RL on back) Vout LPF 17,35,100Hz,Ext Gain x1k,2k,4k,6k,Ext HPF 0.05,0.5,2Hz ac dc Sel OPA U2 CM Breadboard Area Right Arm Pad, Vin+ of IA Vcm, +, -, or Com Select 3 R Div Can Convert Single-ended to Diff Instrumentation U1 Amplifier 1st Stage Gain OPA U3 2nd Stage Gain +5V LDO U7 TPS71550 Speaker

  28. A Precision Low-Level DAS/ECGCardiotachometer Demo Board – back side This Demo Board Supports Many Applications Brief Instructions Easy-to-Use Pin Sockets (No Soldering) Speaker +9V Battery Left Arm Pad, Vcm from IA, -Vcm, +Vcm, Com Breadboard Area

  29. Low-Level DAS / ECG CardiotachometerDemo Board - Standing Gently Hold Electrode Pad Areas (relax fingers), Standing can be ok. Sit Down if Possible

  30. A Precision Low-Level DAS/ECGCardiotachometer Demo Board Additional Applications • Industrial pressure, temperature flow and humidity and general sensor signal conditioning • Medical diagnostic and biophysical monitoring • Analytical and scientific instrumentation • Communications sensor and signal amplification • Automotive sensors

  31. A Precision Low-Level DAS/ECGCardiotachometer Demo Board Vref Puffing Pressure Tube Pressure Bridge Application Quickly Puffing on Tube ac-Coupled

  32. Low-Level DAS / ECG CardiotachometerDemo Board – Puffing Pressure Bridge 0.1uF 0.1uF + Cb1 Cb3 - - - - +5V + + + 8 Silicon Microstructurers Inc. Milpitas, CA, Press Bridge SSM5410-005-G-P 408-577-0100 Stage2, Gain = 600 GT = 2000V/V Stage1, Gain = 5 22pF R1 Vref = +5V Vin- R4 C2 390k 1k +5V U1 +2.5VCM Vbrg offset = 43mVdc 1M 1 7 Vout 2 R18 2 C1 1 R6 INA326, 327 (shtdn) R/R I/O Self-Zero 5 (+) A3 100pF - = Vin x Rgain total 1 40.2k 4 2 (-) 6 3 Vout INA 3.3k 8 High Pass Filters (dc restoration) ΔVin 1.5mVP-P 0.15 – 2.4mVP-P 2.5VDC ± 1.5Vp 1.0 to 4.0V ac Hold 3 40.2k + 4 R7 5 Vin+ R2 R11 3..01M 0.05Hz C5 R10 3,4 R5 390k 1k 470pF 200k C3 20k 22pF ac 5 +2.5VCM +5V +2.5V dc 7 +5V supply 2 U3 Vdc pedestal ½ Vsup Vcm + A4 R19 8 1 Spec is 100mV diff out for 5psi input:0.75mVp out for 0.0375 psi input 20k OPA2335 Self-Zero A1 6 C6 R20 4 3 U2 47pF C4 ac-Coupled Removes 43mVdc brg offset R8 OPA2335 Self-Zero R9 20k 390k 6 7 390k 390k 390k A2 +2.5V dc +2.5V R3 Vcm - 5 Power Supply Common-mode Volt = (Vin+ + Vin-)/2 (high inverting gain) Analog Circuit Common (NOT USED) It’s possible to omit A1, depending on resistances. (isolated from earth ground) +Vs -Vs

  33. Low-Level DAS / ECG CardiotachometerDemo Board – Puffing Pressure Bridge Vin- INA +5V Excitation Directly From Sub Regulated Supply Gtotal = 2kV/V 2Hz to 17Hz BW +5V Pressure Bridge Vin+ INA NOTE – Same Phase - Bridge (2) Out => Vin+ INA + Bridge (5) Out => Vin- INA Makes Vout Have Same Phase as Vin diff That is Vout 2nd Stage Increases When Vin- INA Increases With Respect to Vin+ INA Plugged Into ac-Coupled Position 5mmHg, 0.0375psi Change When Puffing ac-Coupled Puffing Pressure Input Same Phase Mechanical Pressure Gage

  34. Low-Level DAS / ECG CardiotachometerDemo Board – Puffing Pressure Bridge 0.2 second per puff 300 puffs per minute Actual Pressure Puffs 0.75mVp-p Input G = 2,000V/V 1.5Vp-p Ouput SIGNAL 1.5Vp-p ac +2.5V Offset 0.0375 psi from Bridge 0.2 second Puffs Scope Trace 0V Peak-to-Peak Detector on Pressure Puffs +4V 0V 2nd Timer 100ms, 1kHz Burst Osc Out ac-Coupled Ckt Amplifier BW = 2Hz to 17Hz Same Phase

  35. A Precision Low-Level DAS/ECGCardiotachometer Demo Board Vref Squeezing Circuit Uses OPA336s Instead of OPA335s Tube Pressure Bridge Application Slowly Squeezing on Tube dc-Coupled

  36. A Precision Low-Level DAS/ECGCardiotachometer Demo Board dc-coupled dc bridge offset (Normal-Mode voltage) is not removed Vout ac + dc Bridge offset will shift output voltage up or down +4.9V max swing Output Signal +2.5V mid scale 0.1V min swing time In single supply circuits, a mid-scale offset is used with the amplifiers to assure linear operation.

  37. Low-Level DAS / ECG CardiotachometerDemo Board – Squeezing Pressure Bridge 0.1uF + Cb3 - - - - +5V + + + 8 Silicon Microstructurers Inc. Milpitas, CA, Press Bridge SSM5410-005-G-P 408-577-0100 GT= 100V/V G1= 100V/V G= 2(R10/RG) G2= -1V/V 22pF R1 Vref = +5V Vin- R4 C2 390k 1k +5V U1 +2.5VCM Vbrg offset = 43mVdc 1M 1 7 Vout 2 R18 2 C1 R6 1 5 (+) A3 100pF - = Vin x Rgain total 1 40.2k 4 2 (-) 6 3 Vout INA 3.3k INA326 RG = 4.21k 8 High Pass Filters (dc restoration) ac Hold 3 RA 40.2k [RA ║(R6+R7)] + 4 R7 5 Vin+ R2 R10 200k R11 3..01M 0.05Hz C5 3,4 R5 390k 1k 470pF C3 20k 22pF ac 5 +2.5VCM +5V +2.5V dc 7 +5V supply 2 U3 Vcm + A4 R19 8 1 Spec is 100mV diff out for 5psi input:0.75mVp out for 0.0375 psi input 20k OPA2336 not used A1 6 C6 R20 4 3 U2 47pF C4 R8 dc-coupled amplifies 43mVdc bridge offset OPA2336 not used R9 20k 390k 6 7 390k 390k 390k A2 +2.5V dc +2.5V R3 Vcm - 5 Power Supply Analog Circuit Common (isolated from earth ground) +Vs -Vs

  38. Low-Level DAS / ECG CardiotachometerDemo Board – Squeezing Pressure Bridge Gtotal = 100V/V dc #2, +2.5V Excitation Buffered Through Op amp Vin- INA +2.5V Or +5V #1, +5V Excitation Directly From Sub Regulated Supply 17Hz BW Circuit Uses OPA336s Instead of OPA335s for Op Amps Vin+ INA NOTE – Opposite Phase + Bridge (5) Out => Vin+ INA - Bridge (2) Out => Vin- INA Makes Vout Have Opposite Phase as Vin diff That is Vout 2nd Stage Decreases When Vin+ INA Increases With Respect to Vin- INA INA326 RG = 4.02k OPA336 RF = 1M Plugged Into dc-Coupled Position dc-Coupled Pressure Bridge Slowly Squeezing Tube Opposite Phase Pressure Tubing T-Connection

  39. Low-Level DAS / ECG CardiotachometerDemo Board – Squeezing Pressure Bridge Actual Slow Pressure Squeezes Scope Trace #1 +5V on Bridge SIGNAL, with +5V Bridge Excitation 0.99V out  G=100 = 9.9mV in => 0.255psi bridge 0.99V #2 +2.5V on Bridge SIGNAL, with +2.5V Bridge Excitation 0.51V out  G=100 = 5.1mV in => 0.495psi bridge 0.51V Half signal amplitude, due to half excitation voltage 5 seconds Vdc offset + Vac sig 43mV + 0.99V 2nd Timer 100ms, 1kHz Burst Osc Out 0V Slow Squeeze +4V Pulse Triggered P-P Detector 0V dc-Coupled Ckt Opposite Phase Amplifier BW = dc to 17Hz

  40. A Precision Low-Level DAS/ECG CardiotachometerDemo Board - Optical Relative Blood Pressure Monitor +Vcc + - -Vcc BP Mech 499k +2.5V +2.5V - - + + Optical Finger Plethysmograph Records Volume Changes Due to Blood Flow BP is Measure of Heart as a Mechanical Pump +5V Single Supply Stage1, Gain = 5 22pF +2.5V dc 390k 1k Vin- +5V Vsig 7 2 100pF - INA326, R/R I/O Self-Zero 1 40k 6 Finger Photodiode 8 499k 3 4 40k + 5 +2.5V dc Light Source Lamp or LED +Vcc 390k 200k Heart 1k 470pF Vin+ 22pF 6 -Vcc 7 +5V 2 A4 8 1 A1 5 499k 4 3 47pF 20k 390k 6 7 +2.5V dc Photodiode Examples 390k A2 +2.5V dc Vishay/Telefunken BPW34, 7.5mm2 Area Hamamatsu S1227-BR, S2387-16R, 6.49mm2 Area TI OPT101, Just PD, 5.2mm2 Area 5 (high inverting gain) Right Leg Drive Amplifier It’s possible to omit A1, depending on resistances.

  41. A Precision Low-Level DAS/ECG CardiotachometerDemo Board - Optical Relative Blood Pressure Monitor ac-Coupled Photodiode Inside OPT101 (Can Use Separate Photodiode) Gt=6kV/V 17Hz 2Hz ac-Coupled OPT101 Photodiode Connected to 3-R Divider to Create Differential Input Voltage Differential Input Voltage

  42. A Precision Low-Level DAS/ECG CardiotachometerDemo Board - Optical Relative Blood Pressure Monitor 0.94 second per beat 64 beats per minute 0.12mVp-p Input G = 6,000V/V 0.7Vp-p Ouput Actual Finger BP SIGNAL 0.7Vp-p ac Optical +2.5V Offset 1st Timer Trigger Input 0.94 second Scope Trace 0V Peak-to-Peak Detector on Blood Press Max 1st Timer Output 0V 2nd Timer 100ms, 1kHz Burst Osc Out 0V Missing Sound Burst Did Not Trigger P-P Detector or Maybe DIGITALO-SCOPE Abnormality

  43. A Precision Low-Level DAS/ECGCardiotachometer Demo Board The low-level DAS/ECG demo board: • Provides a useful platform for low signal level circuit development. • Is useful as a portable, self-contained cardiotachometer. • Demonstrates the ability of very small amplitude signals to be amplified in the presence of large common-mode signals. • Provides either AC or DC coupling, but very large gain may be difficult to use for DC due to offset. • Accommodates a variety of medical and non-medical sensors and applications.

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