SIGNAL SOURCES FOR SIMULATION, TESTING, AND CALIBRATION - Design and Development of Medical Electronic Instrumentation - page 255

Figure 6.6 Synchronous signals can be added by connecting more channels to the clock data bus. This figure shows an oscilloscope print-
out obtained from a two-channel cardiac signal generator set to simulate a patient's ECG and left-ventricular blood pressure signals.

The cuto ff frequency of the output low-pass fi filter should be selected to be at least half

of the sampling rate. Then, for 25 Hz /2 1/2 π (R24)(C13), and selecting C13 0.1 µ F,

R24 resistor. If a heart rate of

60 beats/min is chosen, R19, R20, C4, and C5 have to be selected to cause the trigger clock
multivibrator to oscillate at 1 Hz. If C4

127,323 Ω , which can be approximated by a 130-k Ω

C5 10 µ F and R19 100 k Ω , R20 needs to set

to yield a period of 1 s.
The capability of generating one or more synchronous signals can be added by con-
necting more channels to the clock data bus. This is especially useful when working with
multiparameter monitors. In Figure 6.6, which shows the output of a two-channel cardiac
signal generator, channel 1 simulates the surface ECG and channel 2 simulates a catheter-
measured left-ventricular pressure waveform.

somewhere near 43 k Ω

DIGITAL GENERATION OF ANALOG WAVEFORMS

More complex, nonstandard, real-world stimuli waveforms can easily be created as a
numerical array and played back through a digital-to-analog converter (D/A or DAC) to
yield analog waveforms of arbitrary complexity. This is the operating principle of a digi-
tal arbitrary waveform generator, or arb . Despite the simplicity of the concept, a PC pro-
gram that would copy digital values stored in an array into a DAC would severely limit the