J2217 sound velocity measuring instrument is used to measure the propagation speed of sound in different propagation media, and also can measure the frequency of sound. The instrument is mainly composed of two sound sensors, a trigger, a sound source, two brackets and 4 wires, and is used in conjunction with the J0201 digital timer. 1. Working principle The trigger of J2217 sound velocity measuring instrument is composed of acoustoelectric conversion circuit, frequency selective amplifier circuit, shaping circuit, trigger output circuit and latch circuit. The schematic diagram of the whole machine is shown in the attached drawing. The circuit has two identical channels, and its working principle is exactly the same. Let's take one of them as an example. 1. Acoustoelectric conversion circuit When there is sound, the sound pressure generated by the sound wave mechanically deforms the piezoelectric ceramic sheet B1, and a weak voltage signal is formed on both surfaces of the ceramic sheet to complete the piezoelectric conversion function. 2. Frequency selective amplifier circuit The frequency selective amplifier circuit is composed of V1 ～ V4 and peripheral components. The faint audio voltage signal generated by 81 is firstly amplified by frequency selection by v1, and then amplified by V2, V3 and V4, and then output from the collector of V4. The C1 and Lt loops connected to the collector circuit of the triode Vl by the frequency selection network select the audio signal with the natural frequency of the piezoelectric ceramic sheet to amplify, so as to improve the anti-interference ability of the instrument and prevent the interference of other sound sources to the instrument. In order to reduce the burden of the frequency selective amplifier circuit and prevent the interference of the post-stage pulse circuit to the frequency selective amplifier circuit, an emitter follower V5 is provided after V4, and the amplified audio signal voltage is output through the emitter of V5 and sent to shaping Circuit IC1. 3. Shaping circuit The voltage signal output by the V5 emitter is shaped by two NOT gates of IC14069, and then a steep rectangular wave is output along the front and back. 4. Trigger output circuit The trigger output circuit is served by the dual D flip-flop IC24013. Before starting work, first set the reset switch S2 to "1", and the S trigger end of the D flip-flop is "1". The R trigger terminal is always "0" because of grounding. At this time, the output terminal is "1", and the LED V15 lights up, indicating that the trigger has been reset (v15 means the signal indicator on the panel is lit, indicating that the instrument is ready, Wait for the sound signal to arrive). Then, set the reset switch S2 to "0", both the S and R trigger ends of the D flip-flop are "O", and enter the working state. When the upper edge of the rectangular pulse output by the shaping circuit IC1⑩ pin reaches the CP pin 11 pin of IC2, the D flip-flop is triggered to flip. The Q terminal of IC213 pin changes from "1" to "0". This signal is coupled to the base of V7 via DC blocking c3. The output phase must be selected by the output selector switch before it can be output in order to match the digital timer. The internal power supply of J0201 digital timer is generally divided into two types of + 12V and -24V. The former requires the use of an upper jump voltage to trigger the digital timer, and the latter uses the lower jump voltage to start the digital timer. When the internal power supply is + 12V type, the output selection button switch S3 on the trigger should be pressed. At this time, v7 works in the collector output mode, inverting and amplifying the lower jump voltage sent to the base, becoming positive Trip voltage output. When the internal power supply is a 24V type, the output selection button switch s3 on the trigger should be popped up. At this time, v7 works as an emitter follower in the form of emitter output, and still outputs the lower jump voltage for digital timing Device. The pulse width of the lower jump waveform is determined by the resistor-capacitor networks R9, R10, and C3 at the input end of the transistor V7. When the Q terminal of IC2-13 pin has a down transition and becomes a low level, the transistor V6 is cut off and LED1 goes out. Indicates that the sonic signal has arrived, and the timing work begins. When the sound wave reaches the second sound sensor, the second signal indicator LED2 also goes out, indicating the end of the timing work. 5. Latch circuit Because the sound wave makes the audio voltage signal generated by the piezoelectric ceramic piece impossible to be a single wavelength, it cannot be a single rectangular pulse after frequency selective amplification and pulse shaping. The rectangular pulse train will cause the D flip-flop to work continuously, so that the rectangular pulse train will be output on the Q terminal of IC2. This will cause the J0201 digital timer to continue to receive trigger start and stop pulses and fail to work properly. In order to enable the D flip-flop to stop working immediately after outputting a valid trigger pulse. The latch circuit must be set. The latch circuit is served by v6. When the reset switch s2 is set to "1", the Q terminal of IC2 is "t", V6 is saturated and turned on, so that the preselected frequency-selection amplifier circuit obtains the operating voltage. The frequency-selection amplifier works. Once the start signal is shaped as the first rectangular pulse to trigger the flip-flop flip, the O terminal of IC2 immediately becomes low level. V6 is cut off, the pre-selected frequency selection amplifier circuit loses its operating voltage, and stops working. The signal voltage of the signal is discarded, and the output of the locked IC2 remains unchanged. At the same time, the signal indicator goes off, indicating that the timing work is stopped. 2. Troubleshooting 1. Insert the battery into the trigger and close the power switch. The reset switch is set to the "reset" block. The indicator light is off. The fault comes from the power supply circuit, D flip-flop circuit and self-locking circuit. 2. The trigger reset switch is set to the "working state" block. After the bell sounds, the two signal indicators on the trigger panel do not go out. The fault location is in the acoustoelectric conversion circuit, frequency selective amplifier circuit, NOT gate, etc. Gaming chair,High Quality Gaming chair,Gaming chair Details, CN Queen Furniture Co., Ltd. , https://www.queenfurnitures.com