Monday, December 27, 2010
Weak current College】 【e-mail technology experimental debugging and troubleshooting】.
<br> <br> Circuit after installation, do not hurry to power-on test, but first must do the following checks before debugging. <br> <br> 1. check wiring situation) <br> <br> For installation in .the printing plate on the experimental circuit, although usually line number is not very much, but still inevitably, wiring errors are inevitable. Frequently encountered an error (ie, one end of the line is correct, and the other incorrect answer), fewer ( .refer to installation missed line) and more (in circuit completely superfluous line), and so connection error. Check the wiring of the general principle of direct control circuit diagrams, but where circuit wiring more, you can to components (such as amplifier, triode .) as the Center, followed by prosecution questioning their PIN for line, this will not only find error received or fewer lines, but also easier to find the extra lines. To ensure that the line of reliable, in the search line at the same time ., you can also use multimeter resistance stalls on wiring for connectivity check, and the best in devices measure leads, that may identify some "hidden" virtual welding. <br> <br> 2). check components installation <br> <br> .Components of the examination, the focus to the integrated amplifier, transistors, diodes, capacitors, and other leads and whether it has received the wrong polarity, and whether the short-circuit between leads and also to check the reliability of components and the welding point .. Here it should be noted that, in the welding, you must filter on the components to avoid trouble for debugging. <br> <br> 3). check power input and the public has short circuit between the grounding Terminal <br> < .br> On the power front the multimeter check power input and whether short circuit between, if you need to further examine its causes. In the completed the above checks and confirmation are correct before you power on debugging, but you should be aware of the power .of positive and negative resistance cannot be reversed. <br> <br> 2. debugging method <br> <br> Debugging method is typically used after the FBI first min transfer (total). Because for any complex circuit, are some of the .basic cell circuit, therefore, debugging can follow the signal to flow to and from the former to back gradually adjust the cell circuit. The idea is to be gradually to the whole, that is, step by step through each unit circuit debugging, gradually expanding .the scope, the last complete debugging machine debugging. Using this method of debugging the biggest advantage of timely and accurately identify and resolve issues, and new design of the circuit generally use the method of debugging. <br> <br> In accordance with the .principle of the transfer, the specific debugging steps are as follows: <br> <br> 1 power on observation). <br> <br> First DC regulated power supply to the requested values, and then access circuit. At this point there .is no exception on circuit, including no smoke, whether there are abnormal smells, touch components are Perm, as well as the power supply has been short, etc. If an exception occurs, you should immediately power off and wait until the fault is corrected .to power up again. After power on, confirm that the circuit has been able to measure before they turn into normal debugging. For electronic circuits, it is an important feature of both AC and DC and DC is a circuit to work properly. Therefore, .regardless of whether the FBI is transferred, you should follow to reduce static and dynamic principle after the transfer. <br> <br> Static debug 2). <br> <br> The so-called static debug means that there will be no .external signal conditions the DC testing and adjustment process. Usually prevent outside interference cuanru circuit, the input side and between the often shorted. Measurement of static work of basic tools are easy to measure a multimeter, often with multimeter measuring DC voltage rail c, b ., a transistor e-to-ground voltage, and then calculate the tube of the collecting electrode electric current, the static parameter. But the test, you must always take into account the internal resistance of the multimeter voltage rail test circuits, eg 500 - .multimeter DC voltage of the internal resistance as stalls 20 K Ω / V, so the internal resistance of 2.5V files to 20 K Ω / V × 2.5 V = 50 K Ω V, 50V stalls to 1 M Ω. By static testing, you .can discover has damaged components, judgment circuit work status, and timely adjustment circuit parameters with circuit working state meet the design requirements. <br> <br> Dynamic debug 3). <br> <br> Dynamic debug is on the basis of static .debugging. In circuit input access rate and frequency of the sine wave voltage, suitable for, and then uses the signal trace method, which uses the oscilloscope and Millivolt meter along the direction of signal delivery, recursively checks all relevant points of the waveform and the .size of the signal voltage, identify problems and to be adjusted. In the dynamic test type in the process, the oscilloscope's signal input methods are best placed in the "DC", this can be through direct coupled manner while observing the measured signal AC, .DC components. Circuit in the dynamic work, it should be noted that the amplifier level is between before and after each other. The front-stage amplifier equivalent after the class amplifier the signal source, then the preamplifier is the front-stage amplifier load levels .between output and input resistance interaction, interrelated. In addition, the dynamic adjustment on the process, often under test waveform, circuit working point to make appropriate adjustments, to all levels of circuit can better perform its function. In the experimental debugging, all test .equipment grounding port should be and experimental circuit ground-side connection with the introduction of interference, not only will the work of the experimental circuit status change and will use the results of measurement errors. <br> <br> In electronic circuit design, installation .and debugging process, inevitably there will be a variety of symptoms, so check and troubleshoot electrical engineering staff is necessary practical skills. Faced with a whole circuit, from a large number of components and lines quickly and accurately identify faults, this does not lead to .a failure, but is also very diverse, this requires mastering the right way. In General, the troubleshooting process is proceeding from the symptom, made by repeated testing, analysis and judgement, and gradually find out the cause of the failure. The following troubleshooting .in a discussion, not before the method-first look at some of the common symptom. <br> <br> 1 common failures). <br> <br> A £ ® test equipment failures that may have the test device is faultyThe function .failed or the right to use the test rods damage cannot test; and may the operator on the instruments used incorrectly caused the failure, such as an oscilloscope knob-level select wrong, resulting in abnormal or even no wave waveform. <br> <br .> B £ ® circuit components itself caused as a result of the failure. Such as resistors, capacitors, transistors and integrated devices, and other characteristics of a bad or damaged. This causes symptoms often have output into the circuit without output or output exception. .<br> <br> C £ ® human-caused the failure. If the operator will connect next wrong or missed, not received, component parameters wrong, triode tube-type confusion, diode or electrolytic capacitor polarity reversed, and so on, may .lead to circuit and is not working properly <br> <br> D £ ® circuit fault caused by poor contact. Such as welding soldered, docking point of contact is not secure, potentiometer sliding end bad, bad, and the grounding was lead breakage ., etc. This causes trouble in General is intermittent or instantaneous, or suddenly stop working. <br> <br> E caused. various kinds of interference. The so-called interference refers to external factors on the circuit there is signal resulting disturbance. .Great variety of sources of interference, often have the following <br> <br> ① received improper introduction of interference is located. Such as grounding line of resistance is too large, the circuit and current to flow through the various parts of the Earth wire .will produce an interfering signal, which affects the normal operation of the circuit. Reduce the interference of effective measures to reduce the ground resistance, generally use more thick copper wire. <br> <br> ② "win" is suppressing noise and prevent the .interference of an important means. The so-called "common places" are all grounded in the circuit of the components have to be connected to the power of potential reference point. In positive polarity single supply circuits, power of anode is a potential point of .reference in negative sexual; single supply circuits, power cathode; potential reference point: the positive and negative than power supply circuit, with two power supply polarity threaded point as a potential point of reference. <br> <br> ③ DC power supply filtering .poor introduction of interference. Various electronic devices in general are 50Hz voltage after voltage of rectifier, filter and get the DC voltage source. But this DC voltage with frequency 50 Hz or 100Hz pattern ripple voltage, voltage range is too large, will be introduced to .the circuit. This interference is a regularity, to reduce this noise, must be in line voltage amplitude small regulated power supply or introduced filtering network. <br> <br> ④ inductive interference. Interference through distributed capacitance coupled to the circuit, the formation .of electric coupling interference; interference by inductively coupled to the circuit, the formation of magnetic coupling, the formation of magnetic coupling interference. These interferences are sensitive to interference. It will cause a parasitic oscillation circuit produces. Exclusion and avoid such interference method is: .the use of shielding measures, shielding shells to earth; the second is the introduction of compensation network, caused by the interference suppression of the parasitic oscillation holding. Specific approach is appropriate in the circuit location access resistance and e-series or single capacitor network, .actual parameter size can be determined by experimentation and debugging. <br> <br> 2). check troubleshooting basic method <br> <br> A £ ® direct observation method of direct observation method refers not to use any instrument, but only use .one's sight, hearing, smell and directly touched components as a means to identify problems, search and analysis of the failure. <br> <br> Direct observation of and the power of pre-screening and power on two aspects. <br> < .br> Power on the main check instrument before selecting and using is correct; the power supply voltage value and polarity for compliance; transistors, diodes and pins and PIN are error-free IC received; electrolytic capacitor of polarity is reversed; there is no interoperability .between components against short circuit; wiring is reasonable; printing plate with wuduan line, etc. The main observation after power DC regulated power supply on current indicates whether the value exceeds the circuit rating; components are Perm, the smoke; no smell of transformers, .etc. <br> <br> This method is relatively simple and effective, it can be used as a preliminary check on the circuit. <br> <br> B £ ® parameter testing method parameters with the help of instruments to help find problems ., and apply the theoretical knowledge analysis to identify the cause of the failure. Usually use multimeter check circuit of quiescent point in relation to the application of that test method. When you find the design values measured and vastly, analysis for issues until resolved. < .br> <br> C £ ® signal tracking method <br> <br> In the debug circuit input amplitude and frequency of access appropriate signal (such as in analog circuits in common f = 1KHz sine wave signal), use an oscilloscope, and .follow the signal to flow to and from the former to back-level progressive observation voltage waveform and amplitude changes, such as which level exception, then the fault is in the line, then effective vector for further examination. This method applies in General to various .circuit. Application in dynamic debugging more widely. <br> <br> D £ ® contrast method <br> <br> Suspect a circuit problems, you can use this circuit parameters and working conditions and the same normal circuit for a comparative analysis from .a failure to determine the point of failure. <br> <br> Replaced by e. <br> <br> The so-called parts replacement method, is the use and fault circuit with the type of circuit parts, components or Board to .replace the failed portion suspected in the circuit, so you can narrow the scope to quickly and accurately identify the point of failure. <br> <br> F.-breaker method <br> <br> Circuit breaker method is used to examine the .most effective short circuit fault. It is also a narrow scope. In General, finding fault in general practice: first direct observation of the law, excluding the obvious failure. Which in turn uses the universal table (or oscilloscope) to check the quiescent point .. Last available signal traces on the circuit for dynamic checks. <br> <br> <br>.