Electronic pulse tester that can measure the number of times per minute, pulse rate, and intuitively display, very easy to use. When not, S the power off, the entire circuit does not consume static power, a 6V battery stack can be used for a long time.
  How it works:
  Figure 1 for the block diagram; Figure 2 as an electrical diagram.
  Produced by piezoelectric sensor pulse signals into electrical signals. Because the signal is weak, so use with non-linear amplifier comprising gate F1 amplifies the signal and then amplified by the non-gate F2 into the plastic, then into the IC2 (CD40110) The addition of the input count to count. CI2, IC3 can count, the decision by the end of their lock: When the lock side is low, allowing the count pulse input; when the lock side is high, the counter is locked, you can not count. IC4 (5G7555) composed of timing, the output terminal and the IC2, IC3 lock, usually 5G7555's pin output high, IC2, IC3 count against, when the SI is click, the 3 pin output goes low , the capacitor C2 charging time by R2 began, IC2, IC3 allowed into the counting pulse. After 60 seconds, IC4 end time, turning the output is high, the counter stops counting, LED digital tube to show a 1 minute pulse of the times. C4 and R3 form a clear circuit connected to the moment in the S, so IC2, IC3 complex zero.

Component selection and fabrication
  IC1 with CD4011 or TC4011BP; IC2, IC3 by counting, decoding, driving triple circuit CD40110; IC4 using 5G7555; display with common cathode dual digital tube; Sensors HTD-27, which shielded cable with F1; the surface of the ceramic core wire solder, solder in the copper shield on the skin.

The instrument use, the first power switch S turn, then piezoelectric pulse in