BIOINSTRUMENTATION Seminar Notes Bioinstrumentation Physiological Variable Transducer Amplifier

BIOINSTRUMENTATION Seminar Notes

Bioinstrumentation Physiological Variable Transducer Amplifier Display Device Quantity to be E 1 to E 2 xn Record Measured • Examples of quantities to be measured: Displacement, Flow, Sound, Pressure, Temperature, Voltage, Current • Examples of transducers: electrodes, thermocouples, piezoelectric devices • Examples of recording devices: chart recorder, oscilloscope

Force Transducer • Turns one form of energy into another • The pulse transducer in our lab changes the pressure produced by blood in the fingertip into a change in an electrical current. This change is capture by the Power. Lab and displayed digitally

Data Acquisition • Power. Lab modifies the incoming changing signal from the transducer in a number of ways • This is called signal conditioning – Amplification (to see small signals) – Filtering (low, high and bandpass filtering) – Zeroing (removal of unwanted background voltages)

Sampling • Analog (continuous) signals are converted into digital signals (A to D conversion) so that they can be stored analyzed by the computer software • The analog signal is sampled (at a particular rate/sec) • Sampling rate must be sufficient to faithfully recreate the original signal

Display • The measured values of the physiological variable are plotted by the software (vs time) and lines are drawn between these points to recreate the original continuous waveform

Low Rate Sampling

High Rate Sampling

Measurement of Pulse

Calculating Pulse Rate from Trace • Count number of peaks in a given amount of time. • Perform calculation to determine BPM • Examples 9 beats X 60 seconds = 90 BPM 6 second 1 minute 12 beats X 60 seconds = 90 BPM 8 second 1 minute

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