3-41
The electrical length (sweep time), which is measured from T2 to T3, can be found by multiplying
RC times the number of time constants. Refer to the Universal Time Constant Chart (figure 3-39) again to
find that 57 percent is 0.83TC. By multiplying 0.83 times R1C1, you will find that the electrical length is
approximately 21 milliseconds:
The physical length (amplitude) is determined by subtracting the valley point from the peak point.
This is 9.8 volts in the example (12.8 volts
-
3 volts).
For a sweep generator that produces a more linear output sawtooth waveform, refer to the circuit in
figure 3-45, view (A). R1 and C1 form the RC time constant. Notice that the capacitor charges toward 35
volts (VE) in this circuit.
Figure 3-45A.—Improved unijunction sawtooth generator.
Figure 3-45B.—Improved unijunction sawtooth generator.
