附录A
Electromagnetic relay detecting
Check the contact resistance.1 blocks use multim eter RX,electric resistance value,regular value measuring relay normally closed conact should be 0;Use multimeter to measure Chang come untied contact electric resistance value,value or the infinity,shows being contact`s turn to already oxidized or touched point already by erosion then.
Check electromagnetism relay coil electric resistance value. When the relay is regular, whose electromagnetism coil electric resistance value is 25 ~ 2 K
. Lower
electromagnetic fixed voltage relay, the coil electric resistance value is less; Higher electromagnetic fixed voltage relay, the coil electric resistance value is relatively bigger. If measuring such that relay electromagnetism coil electric resistance value is an infinity, explain that the coil being a relay's turn already opens a way damaging. Regular value is a lot of if measuring such that the coil electric resistance value is lower than , is to have the short circuit malfunction in the inside of coil then.
Estimate the voltage attracting small side door voltage and releasing. After the both ends will the relay electromagnetism coil be measured connects up 0 ~ 35 dyadic adjustable V direct-current stabilivolt power source (electric current is 2 A) , stabilivolt power source voltage is complied with again low gradually raise, think that voltage now value is to be (or sucking approaching) a relay agrees well with voltage when hearing the relay contact attracting small side door action sound. Be to attract 1.3 ~ 1.5 times agreeing well with voltage like fixed operating voltage. After
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the relay contact attracts the small side door, voltage reducing electromagnetism coil both ends again gradually. The relay contact releases the ding-dang tune till some one voltage time value , this voltage is voltage (be to attract 10% ~ 50% of small side door voltage in general) for the relay release.
Estimate the electric current attracting small side door electric current and releasing. One end will the relay electromagnetism coil be measured receives 1 milliampere of galvanometer positive pole string , the negative pole with stabilivolt power source joins electromagnetism coil another one end , on after the line receiving 10 one K
string winds a potentiometer power source queen, the
potentiometer hindering is worth from the maximum the tune is gradually small , When a certain resistance to relay moves to open its regular contact closure, Now the galvanometer numerical reading is to be that the relay sucking closes electric current (be to attract the 2 times closing electric current like the relay working current). Hindering enhancing a potentiometer still slowly is worth , galvanometer numerical reading is electric current for the relay release when the relay contact releases ding-dang abruptly from attracting small side door state. A relay is disconnected from to measuring a circuit , is use the multimeter electricity to obstruct the direct-current electric resistance value measuring the electromagnetism coil , is use the electric resistance measuring to take advantage of that with the relay working current, being is the relay operating voltage value.
Electrical resistor ,capacitor and oscillator
Though the electrical resistor , the capacitor have composed important electronic circuit component, mimic a few knowledge about electric resistance, capacitance being also to be necessary very much.
Resistor with resistance: Resistance is a two-terminal components. In its present two-terminal between the voltage drop and current flow is directly proportional to it. Ohm resistance value units (
), it is the voltage on the current ratio. Ohm's law as
.
the voltage and current relationship between an equation can be used that
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Resistor resistance can be divided into fixed and variable resistors, resistor also can be divided into linear and nonlinear resistors.
Is called the resistance to the electric current resistance. And expressed with alphabetic character R. The resistance unit is an ohm, this terminology often uses for to express. 1
definition is: When adds to the conductor the voltage is 1V, the
conductor current limitation is the resistance value which 1A needs. The great resistance value commonly used kiloohm (K
) and the megohm (M
) expressed.
Capacitor and electric capacity: The electrical energy can have in the electric field, has this kind of ability component to call it the capacitor. Capacitors usually according to its medium classification, for example paper, glass, ceramics and so on. The electromotive force is big, the capacitor saves the electric charge are also more. Capacitor's capacity is bigger, the frequency is higher, its capacitance is smaller.
Capacitor put aside electric energy ability shouts capacitance. Unless under definitely fixed condition, capacitance is not constant , remembering this one point is very important. Capacitance uses farad (F) to measure. But, farad, this capacitance unit has been very big , has had no way to be used for radio aspect calculation, therefore following (10-12F) generally use tiny law (one-millionth law) and slight.
Oscillator: Can produce the signal part to be called the oscillator. The oscillator uses for to provide the exchange signal, its frequency range from zero yizhi dao in electromagnetic spectrum radiofrequency component peak gigacycle per second region. The oscillator basis has the waveform to be possible to use two methods to carry on the description: Sine-wave generator and relaxation oscillator. The sine-wave generator produces has the sinusoidal waveform signal, the relaxation oscillator usually produces the square-wave signal.
The sine-wave generator has two main parts: Decided that the frequency component and maintains the oscillating part. Usually the decision frequency component is composed of LC or the RC network. Maintains the oscillator part is a transistor amplifier (has electric power supply), this amplifier's input is through such
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as the tuning circuit or the resonant crystal type frequency control part feedback supplies, it must have the enough gain to counter-balance the decision frequency component to weaken, moreover must introduce the phase-shift number of degree which this part needs.
The circuit composes the beginning that the relaxation oscillator has two to link up mutually , every circuital output all can in proper order carry out a switch on another. The switch process is that the edge is continuous , the wave form outputing therefore is the flat direct current wave form continuing being interrupted.
Great majority radio receivers that you use at home all contain oscillator. Every volume X-mitter to air-launch information uses oscillator to come to produce a signal. This apply to the land launching station not only, and apply to X-mitter on steamer or aircraft. Do not only have communication equipment using an oscillator, great majority measuring device signal X-mitter , frequency instrument and et cetera equipment used by you, contain oscillating circuit. You may discover an oscillator on the radar and the circuit equipment.
The sine wave oscillator being put into use in radio communication, to produce a carrier wave broadly, and is used for a lot of radio communication system usage testing instrument broadly. The relaxation oscillator is in TV and radar system , digital system (computer and logic circuit) and the testing instrument are useful as the circuit.
Crystal oscillator specifications
The total frequency difference: within the required timeframe, due to the provisions of the work and all non-working combination of parameters caused by crystal oscillator frequency and the frequency of a given nominal maximum frequency difference.
Frequency-temperature stability: in the nominal power supply and load, the working temperature range in the provisions of the implied benchmark without temperature or with temperature implied by the baseline offset of the maximum allowable.
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Warm-up time Frequency stability: The stability of crystal oscillator output frequency based on power to the output from the frequency of the provisions of the frequency is less than the time required for Tolerance.
Frequency aging rate: in the environmental conditions constant measurement frequency oscillator, oscillator frequency and time relationship. This long-term frequency drift components and by the crystal oscillator circuit elements caused by the slow changes that can be used after the time limit the maximum rate of change (eg, ± 10ppb / day, 72 hours after power up), or the time limit provided for the largest total frequency changes (such as: ± 1ppm / (first year) and ± 5ppm / (decade)) to express.
VCO frequency range: the frequency control voltage from the reference voltage to the provisions of the end of voltage, crystal oscillator frequency to change the volume of the smallest peak.
Voltage-controlled frequency response range: when the modulation frequency changes, the peak shift and the relationship between the frequency modulation. Usually with the provisions of the modulating frequency modulation than the baseline number of dB that the low frequency.
Frequency voltage-controlled linear: the ideal (linear) function compared to the output frequency - input control voltage transmission characteristics of a measure, it expressed as a percentage of the entire range of frequency offset can be allowed to non-linearity.
SSB phase noise ￡ (f): deviation from the carrier f, one phase modulation sideband power density and the ratio of carrier power.
Now each place to enhance safety consciousness, the detection of high precision, high accuracy, easy to carry requirements. Plus the development of gas sensors, microcontroller is characterized by integration limit, smaller pieces (storage capacity, good reliability, expand simple, control function strong and other characteristics, based on SCM alcohol concentration of research and development and production of detector has a wide range of real market and the potential market
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