Abstract: A pulse interval to pulse rate converter for use in a portable, battery-powered, hand-held test instrument useful for evaluating the performance of a pulse generator such as a cardiac pacer or the like. A pulse generator being tested generates output pulses at an unknown rate and it is desired to measure this rate and to visually display same in units of pulses per minute. A count representative of the interval between successive pulses is developed in a first digital counter and subsequently stored in a holding register, thereby freeing the first counter to continue to measure subsequent pulse-to-pulse intervals. A digital downcounter, arranged to be decremented at a fixed high rate, receives the stored interval value and a tally is developed in a display counter of the number of times that the interval value can be decremented to zero within a known time period, e.g., one second. The count developed in the display counter thus corresponds to the rate value expressed in units of pulses per minute (ppm).

Abstract: Apparatus for measuring the amplitude of an adjustable width current or voltage impulse at a known time interval following the initiation of the impulse. During a first pulse duration, a counter is advanced with clock signals having a frequency f.sub.1. The total number of clock signals accumulated during the interval is then transferred into a downcounter which is arranged to be decremented during a second identical interval by a clock signal having a frequency n (f.sub.1). When the downcounter reaches zero, a strobe pulse is produced for enabling the analog measuring circuits which sample the amplitude of the current or voltage impulse being monitored. By selecting the value n, the sampling point can be shifted in time along the width of the pulse being measured. For example, for n=2, the amplitude of the voltage or current pulse being measured will be that occurring at the midpoint of the pulse.

Abstract: An electronic test instrument for measuring the refractory interval of a demand-type cardiac pacer pulse generator. The normal pulse-to-pulse interval of the pacer under test is measured by accumulating regularly occurring timing signals in a first counter during the interpulse period. At a predetermined time after the occurrence of the first pulse defining the interval, a pseudo R-wave is generated and applied to the pacer under test. The next pulse-to-pulse interval is then measured in a second counter in a fashion similar to the first measurement and a test is made to determine if the second interval exceeds the first by a prescribed amount. If so, it is known that the pseudo R-wave was effective to reset the pacer's pulse generator. If not, the time of occurrence of the next pseudo R-wave is delayed by a further known amount and the operation is repeated over and over until an extension of the normal pulse-to-pulse interval is noted.