11. Pulse generator Flashcards
11/1. Two-state systems. Generation of pulses, time constant, trigger, types of pulse generators. Function codes of pacemakers. 11/2. Monostable and astable multivibrators in medical practice. Modeling of pacemaker signals. Energy and charge in a pulse.
Describe two-state system
Transition between the resting and activated states is induced by a trigger pulse exceeding the threshold level.
two-state system
What is forbidden state?
The state between the resting and activated states
→ it will fall into either of the two permitted ones
two-state system
Transition between the two states is always evoked by a (1)___,
Signal
-> a pulse that exceeds some threshold level (the falling edge of this pulse may also work).
two-state system
What is a trigger pulse?
a pulse that exceeds some threshold level (the falling edge of this pulse may also work).
What are the three types of pulse generators
monostable, astable and bistable multivibrator
How many stable states does monostable multivibrator have?
1
How many stable states does astable multivibrator have?
0
How many stable states does bistable pulse generator have?
2
Descrive monostable multivibrator
pulse generator producing a single output pulse of determine duration, for every input pulse (trigger) above a threshold.
monostable multivibrator
Other names for monostable multivibrator?
one-shot or monoflop
monostable multivibrator
Triggered by an input pulse, it gives a ___(usually square pulse) of determined duration (Fig. 2)
single output pulse
monostable multivibrator
What is the usual type of pulse of single output pulse?
usually square pulse
monostable multivibrator
The rising edge of the square pulse is induced by the (1)____, but the system returns spontaneously without further (2)___ to its (3)___ (via a dropping edge) after (4)____
- trigger signal
- triggering
- stable state
- the time given by the time delay (T ).
Give an example of monostable multivibrator
Defibrillator
Defibrillator
Let us take a closer look at the possibility of electronic timing (setting the delay time ) with regards to the defibrillator
→ The resistance of the chest is R, at which the capacitor of capacitance C is discharged.
→(1)____flows through the resistance R, and we encounter a (2)___ of similar shape.
- Exponentially decreasing electric current (I)
- voltage U decrease
Defibrillator
Principle of operation of the defibrillator?
Electric pulses with higher energy can be applied with the aids of electrodes placed on the chest
-> generates the synchronized contraction of the heart with the chance to restore the normal heart pace
(The time constant of the pulse can be set by the R (The resistance of the chest) and C (capacitance) elements of the circuit.)
monostable multivibrator
In electronics, the timing of a monostable multivibrator is usually realized by an ___ circuit
RC
monostable multivibrator
In electronics, the timing of a monostable multivibrator is usually realized by an RC-circuit
The (1)___ of a discharging capacitor controls a switching circuit, which turns on and off according to (2)____
→ we obtain a (3)___ pulses of (4)___, set by the values of R, C and/or the trigger level.
- exponentially decreasing voltage
- the trigger voltage level
- square
- controlled durations
Describe astable multivibrator (relaxation oscillator, free-running multivibrator)
- Pulse generator producing a sequence of identical pulses.
- It can be constructed by connecting two monostable multivibrators in a ring.
astable multivibrator (relaxation oscillator, free-running multivibrator)
By connecting two (1)____ in a ring (Fig. 5), we get the astable multivibrator (AMV)
monostable multivibrators (MMV)
astable multivibrator (relaxation oscillator, free-running multivibrator)
Other names of astable multivibrator
free-running multivibrator or relaxation oscillator
astable multivibrator (relaxation oscillator, free-running multivibrator)
The output of the (1)____ (see Fig. 2, falling edge) triggers the (2)____, which subsequently triggers the (3)___ and this process continues on and on.
- first MMV (monostable multivibrators)
- second MMV
- first MMV
astable multivibrator (relaxation oscillator, free-running multivibrator)
The output of the first MMV (see Fig. 2, falling edge) triggers the second MMV, which subsequently triggers the first MMV and this process continues on and on. This way we get a ___
periodic square pulse generator
astable multivibrator (relaxation oscillator, free-running multivibrator)
How to calculate the time period of the AMV?
the sum of the individual active-state durations of the MMV1 and MMV2
astable multivibrator (relaxation oscillator, free-running multivibrator)
The pulse width of the two MMV-s can be adjusted individually by their (1)___ elements
→ a square pulse train of any (2)___ can be produced
- RC
- duty cycle
astable multivibrator (relaxation oscillator, free-running multivibrator)
What is the role of duty cycle?
It determines what portion (percentage) of the time period is occupied by the pulse itself, thus by the activated state
astable multivibrator (relaxation oscillator, free-running multivibrator)
What is the formula of duty cycle?
For the duty cycles of the output signals Uout 2 (see Fig. 5), we obtain:
astable multivibrator (relaxation oscillator, free-running multivibrator)
The contractions of a healthy heart are controlled by electrical pulses similar to those produced by the AMV-s.
→ There are several cells that create these stimuli
Q’s: Give examples for these cells
sinoatrial node (SA node), atrioventricular node (AV node), and the cardiac muscle cells themselves
→ These are called pacemaker cells,
What are pacemaker cells?
The cells that create electrical pulses, setting the pace for blood pumping for heart contraction -> directly control the heart rate
The role of an artificial pacemaker
It is implanted in order to restore the normal heart rate.
artificial pacemaker
The pacemaker itself provides an (1)___ function for a slow or irregular “biological astable multivibrator” (the heart) in order to induce (2)___
- artificial trigger
- contractions at the proper rate
Describe bistable multivibrator
„pulse generator” that requires an input pulse (trigger) for the activation of either of the two stable states.
By connecting several bistable multivibrators in an array, a binary counter array may be constructed.
Other names for bistable multivibrator
- flip-flop
- biflop
bistable multivibrator
The trigger pulse induces a ___
change of the state of the bistable multivibrator
bistable multivibrator
The trigger pulse induces a change of the state of the bistable multivibrator.
What does this mean?
If it was in the state A before, then it is flipped into state B; and if it was in state B then it is flipped into the state A, and will remain in either state indefinitely, unless triggered again
bistable multivibrator
The trigger pulse induces a change of the state of the bistable multivibrator.
This circuit has two equivalent,
What are these equivalents?
2 stable states
Application of monostable multivibrator
Defibrillator
Calculation of pulse energy
Known voltage and tissue resistance, known pulse duration time
- Proportional to voltage and pulse duration period
- Inversely proportional to tissue resistance
(A LONG lasting battery is needed.
A battery change = exchange of the whole device = operation!)
Pacemaker Function codes of Chamber(s) Sensed
Pacemaker Function codes of Chamber(s) Paced
Pacemaker Function codes of Response to Sensing
Pacemaker Function codes of Rate Modulation
Pacemaker Function codes of Multisite Pacing
What is Betavoltaic cell?
β-radiation powered cell.
- the ionization separates charges in a semiconductor junction
