Detector circuit accurately separates and counts phase-shift pulses over wide range of basic pulse-rate frequency, and also provides reasonable representation of full repetitive EKG waveform. Single telemeter implanted in small animal monitors not only body temperature but also animal movement and heart rate

Anderson, M.

English

NASA Technical Reports Server

November 1974	 B74-10196 
NASA TECH BRIEF 0	 Ames Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Heart-Rate Pulse-Shift Detector 
Advances in the state of the art of biotelemetry 
suggest that a single telemeter implanted in a small 
animal can be used to monitor not only body temper-
ature but also animal movement and heart rate. In a 
program of research involving the design of electronic
becomes a more significant deviation in the time pre-
ceding the next pulse and eventually the deviation is 
converted to usable heart-rate data. Ignoring the first 
90% of each pulse period substantially reduces out-
put noise arising from spurious pulses. 
_	 Rate	 Width ______________ 
Pulse	 I Count	 Control	 Variable 
Input	 Meter	 Voltage	 Monostable 
Multivibrator 
Trigger 
circuitry and a data-processing system to monitor 
simultaneously the three circadian periods, a heart-
rate detector circuit was developed which accurately 
separates and counts phase-shift pulses over a wide 
range of basic pulse-rate frequency, and also provides 
a reasonable representation of the full repetitive EKG 
waveform. 
As indicated by the block diagram of the heart-rate 
detector (figure 1), telemeter pulse inputs in the range 
of 200 to 1000 pps, with phase-shifted heart-rate in-
formation, are first directed to a count-rate meter 
circuit which controls a variable-width monostable 
multivibrator; then the included EKG waveform is 
reconstructed. Circuit characteristics are selected to 
give a pulse width of about 90% of the basic pulse 
period over the required frequency range. At each 
input pulse, the multivibrator is triggered for 90% of 
the basic frequency; any small deviation in frequency
Pulse Width
	 Peak	 Output to 
to	 Sample  
Pulse Height and Hold	 Counter 
Converter H Circuit 
Figure 1 Heart Rate Detector 
The source of input to the heart-rate detector is 
indicated in the block diagram of the system for 
monitoring several small animals (figure 2). The im-
planted biotelemeter is basically a relaxation oscillator 
which operates in the low-frequency rf band. The 
pulse repetition frequency is a calibrated function of 
animal body temperature, and is further phase-mod-
ulated by animal heart beats. The modulated rf sig-
nals are received by three orthogonally-oriented 
loop antennas, then separately amplified and directed 
to broadly-tuned AM detectors. The amplifiers em-
ploy dual-gate FET's with circuit gain suitable for 
subsequent signal processing. Diode switching then 
selects the strongest detected signal for further dis-
tribution to demodulators for separation of temper-
ature-dependent pulse frequency, periodic heart-beat 
pulse shift, and signal strength indications which are 
indicative of animal activity.
S
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19740000196 2020-03-17T13:52:00+00:00Z
Body 
Temp. 4,_.i__. Heart Beat 
4-ACTIVIrY- 
Biotelemeter
	
Channel 
	
and	 Selector
Binary 
Counter 
Cage Temp.	 Antenna/Preamp./Receiver 	 Heart Rate  I	 -	 Assembly - -	 Detector 
Cage Press.	 I	 I 
I Activity Demodulator 	 I
Analog	 A/D 
IMfiIeer	 Convert 
Figure 2. Monitor System 
Note:	 Patent status: 
	
Requests for further information may be directed
	 NASA has decided not to apply for a patent. 
to:
Technology Utilization Officer
	 Source: Mark Anderson of 
Ames Research Center
	 Northrop Corp. /Electronics Division 
Moffett Field, California 94035	 .	 under contract to 
Reference: TSP 74-10196
	
	 Ames Research Center

(ARC-10729)
II 
B74-10196	 Category 01, 05	 0


Heart-rate pulse-shift detector

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