This HC-SR04 ultrasonic module can realize 2 ~ 700cm of non-contact ranging function,
has 5 V of wide voltage input range, static power consumption is less than 3mA. Their
own temperature sensor will revise the ranging and has many communication modes like
GPIO, just like watchdog inside, very stable and compact.
Working Voltage: 5V(DC)
Static Current: Less than 2mA
Output Signal: Electric frequency signal, high level 5V, low level 0V
HCSR04 Ultrasonic Sensor
Sensor Angle: Not more than 15 degrees
Detection Distance: 2 cm to 450 cm
High Precision: Up to 2mm
Input Trigger Signal: 10us TTL impulse
Echo Signal: Output TTL PWL signal
Note: The module has a blind spot of 2cm (very near)
So obstacle held too closely will not be detected.