1, the pin is a multi-purpose pin, which can be used as the output pin of infield scanning pulse; At the same time, the external resistance value can set the sensitivity of synchronous separation of internal magnetic field; At the same time, if no internal field pulse is needed, other field pulse signals can be input from this pin, and the internal field output will be automatically cut off at this time; It is also an automatic trigger mode release switch and a World Bank AFC door release switch.
2. Output 50\60Hz, and judge the field scanning frequency by counting the line frequency inside the integrated circuit. When the frequency is 50Hz, the output level is low; When the frequency is 60Hz, the high level is output. When this pin is used with LA7837\8, the field amplitude can be adjusted automatically, and a fixed level can be given to this pin to make it work at the field frequency.
3. This pin is the filter pin of AFC 1 line, and the DC bias of AFC is H, VCC-3f. In order to improve its power supply wandering characteristics, AFC filter is set on the power supply side. C 1 is the capacitor for eliminating field pulse, R 1 is the resistor for converting control current into voltage, C2 is a smooth filter, and the output of this pin is limited to 2 VF.
relevant information
Ultrasonic wave refers to the vibration frequency above 20KHz, and its vibration frequency per second is very high, exceeding the upper limit of human hearing (20000Hz). People call this inaudible sound wave ultrasonic. Ultrasonic wave and audible sound are essentially the same, and their similarity is a kind of mechanical vibration, which usually propagates in elastic medium in the form of longitudinal wave and is a form of energy transfer.
The difference is that the ultrasonic wave has high frequency, short wavelength, and good beam and directivity. In 20 13 years, the frequency range used for abdominal ultrasonic imaging is between 2∽5MHz, usually 3∽3.5MHz. This cavity is very close to vacuum, and it will rupture when the ultrasonic pressure is reversed to the maximum, and the strong impact force generated by the rupture will knock down the dirt on the surface of the object.