Main Technology Specifications Working Frequency : 2.0 MHZ + 10% Ultrasonic output Power : lob<10 mW/cm2 Overall Sensitivity : > 90 dB (integrated sensitivity 200mm away from the surface of the probe) While measuring integrated sensitivity using the doppler frequency (300 + 50) Hz Reflecting target speed: 10cm / s ~ 40 cm / s FHR measuring range : No narrower than 50bpm-240bpm (+ bpm). (Beat Per Minute) FHR accuracy:+ 2 bpm Spatial-peak temp-peakacoustic pressure:<0.1 MPa. Negative Peak Sound Pressure: (p_) <1 Mpa ob 2 Output Beam Intensity: (I )<20mW/cm 2Spatial-peak Temporal-average Derived Intensity:(I )<100mW/cm spta Continous Working Time:>5h (Low battery capacity or large volume may reduce working hours) 6 2 Coupling gel acoustic impedance 1 5 ~ 1 6 (10 g/cm .s) Auto output power < 1.0 W Battery Type Recommended Two pieces of 1.5 V DC battery ( SIZE AA LR6 ) Working Environment Temperature +5 C ~ +40 C Humidity < 80% atmospheric pressure 86kPa ~ 106kPa Transport and Storage Environment Temperature : -10 C ~ +40 C Humidity < 80% Atmospheric Pressure : 86kpa ~ 106kPa, well-ventilated room without corrosive gases.