Midterm 1
The formula for aliasing frequencies.
What is falias = n*fs +/- f0?
The equation for capacitance in series.
What is Ctot = 1/(1/C1 + 1/C2 + .... + 1/Cn)?
Three ways to minimize micro and macroshock.
What are:
Insulating large-scale conduction paths (bed rails)
adding double/triple insulation on cardiac catheters
electrically isolate patient-connected electrodes from power supply (no secondary path to ground)
ensure current can't exceed 10uA (half of the 20uA injury threshold)
GFCI
establish common ground for devices near patient, insulate hot wire from case, ground case with third wire
Component allowing current flowing through circuit in one direction, with a small vbreakdown, intended to be reverse biased.
What is a Zener diode?
Speed of sound in water/blood.
What is 1500m/s?
Result of truncating in time/decimating in frequency.
What is making frequency resolution coarser, adding ripples to frequency domain, reducing signal length, and losing information?
Reason the maximum gain measured across R in an resonant RLC is not greater than 1.
What is the impedances of L and C are out of phase by 180, so they cancel out and the impedance is equal to R (so gain is 1 at resonance)?
(At frequencies far from the resonant frequency, ZL and ZC do not cancel completely, so Ztotal > ZR, so gain < 1).
The difference between macroshock and microshock.
What is limb-to-limb (>20mA, R = 15kOhm to 1MOhm) vs current focused through the heart (>20uA, Z = 0)?
Ag-AgCl reversibility/irreversibility and polarizable/non-polarizable electrodes.
What is reversible, non-polarizable?
What is, the range of angles outputted- the angle is limited to (-90, 90) for atan, but atan2 returns from (-180, 180)?
What is distinguishing the differences between very small magnitudes (and large magnitudes!)?
What is a no-pass filter?
Switch that automatically opens when difference between current in and current out approaches ~10mA (around water/sinks).
What is a GFCI (Ground fault circuit interrupter)?
What is HIFU?
Two benefits of an instrumentation amp rather than an op amp.
What is higher input impedance, higher accuracy, and low and tunable gain (since the gain is controlled by external resistors)?
Result of truncating in frequency.
What is losing fine details in signal, and causing ripples in time/spatial domain? (low pass filter when truncating!)
The cause of resonance in an RLC filter circuit.
What is perfect exchange of energy between the capacitor and inductor?
Reason we use extremely high freqency (400kHz, for example) for electrosurgery.
What is such a high frequency it cannot affect the heart (potentially unable to cause action potentials)?
Steps of getting a digital signal from an analog signal with a frequency too fast to sample.
What is demodulation (multiply by cos(2pi*f*t)), band-pass filtering (removing the outer two peaks, and at times the top of the peak at the center of the graph), and sampling with the ADC?
What is SA node -> AV node -> bundle of His -> bundle branches -> Purkinje fibers?
Sequence of creating an FIR filter (like homework 3!).
What is taking a sinc function with the correct bandwidth frequency, multiplying by a cosine of the new center frequency, truncating to 2-3 zeroes of the sinc, and applying a smoothing window (hamming/hanning/etc).?
Describe the components and setup of an inductor-based differentiator.
In the inverting input of the op-amp, a resistor and inductor in the negative feedback, and the positive/non-inverting input goes to ground.
Components; op amp, inductor, resistor
Reason cardiac catheters pose electrical risk.
What is current carrying a particle through the aperture, creating a wall of high impedance, causing current to flow through the Rshunt, voltage measured and amplified by the instrumentation amplifier, producing a voltage spike?
(Current passes through the high impedance resistor when there is a particle blocking the aperture.)
Difference between electrode-based sensors and FET-based sensors.