Digital display inductance / capacitance table, Inductance / Capacitance Meter
Keywords: digital display inductive / capacitance table
E-enthusiasts when making equalization capacitors and speaker frequency sensation, will be damaged by slightly errors. Here you introduce a simple inductive / capacitance table, digital display, intuitive, convenient and high precision. First, the principle 1, the parameter transform circuit: The parameter transform circuit consists of 555 time-based multivibrator, which can be converted into the pulse width that is proportional to the element parameters to be met. This has a rectangle having a specific pulse width as a grooming signal, and the pulse width (actually an element parameter) can be displayed by the display of a standard pulse count of a known cycle within the pulse width time. When the capacitor is measured (this, the band switch is 5, 6, 7 bits) is a multi-harmonic oscillator that is a timing element, and the generated rectangular wave is output, and the gate of the counter is sent, the pulse width TW = CRCLN2 . When measuring the inductor (the band switch is 1, 2, 3 bits), is a multi-harmor that is a timing element in LX, when the power is turned on, V2 (6) = VCC, 555 3 foot output low, 7 In the foot, the power supply is charged by the LX of the RL. As charging, V2 (6) ↓, when V2 (6) = 1 / 3VCC, the circuit flips, 3 foot output high level, 7 foot and ground break On, because the LX current cannot be mutated, it will produce a induction electric potential that D1 is turned on, LX is d1, RL discharge, V2 (6) ↑, when V2 (6) = 2 / 3VCC, the circuit is flipped, 5 The foot output is low, 7 feet are turned on, and the LX starts charging, so the 5 pin output duty cycle is 1: 1 square wave, sent to the gate of the counter. This pulse width is TW = lx / rlln2.
2. Standard pulse generator: This circuit is composed of inverters 3, 4 and crystals, and the crystal frequency is 1 MHz, and the standard pulse period is T = 1 μs, which is used as a counter of the counter. 3, count, display circuit: The display consists of three LED digital tubes, and the counter is composed of the MC14553 three dynamic scan counter. The standard pulse of T = 1 μs is sent to the 12 foot of the MC14553. The rectangular pulse generated by the multi-harmonic oscillator is sent to the 11 foot of the MC14553. When the 11-pin is high, the 12-foot standard pulse of 4553 cannot be added, 11 pin is low. Until, after reverse phase, differential, get a positive tip pulse, first to the counter, at the same time, 4553 latch release, start a standard pulse count, etc., then enter the high electricity, the counter is latched, and 10 The feet are also high, the counter data latches, the display is stable to the previous count result, set in this loop to N, then TW = NT is LX / RLLN2 = NT, reasonably selects RL or RC, The display can display LX's micro-envelope or CX number of peel scalp, very intuitive, this instrument LX has a total of 0 ~ 999μH and 0 ~ 999MH, CX has a total of 0 ~ 999pF, 0 ~ 999NF (Na Fa), 0 ~ 999μF Three gears. Second, the key components of the production point are the range resistors RL and RC, 0.693Ω and 1.443Ω two resistors can be wound by line with high strength enamel lines, preferably on the bridge, to ensure 1% accuracy. Other Range resistors can be obtained in parallel with multiple resistance strings, but also to ensure 1% accuracy. Third, debugging this circuit adjustment is extremely simple, just adjusting C2 to make the standard pulse frequency of 1 MHz, after using no school zero. Although the circuit is only displayed with 3 digits, six valid numbers can be displayed. If there is a 47312PF capacitor, only 732pf is displayed in the PF file. After all of the NF files, the display shows 004nf, so the capacitor is 004732PF, that is, 0.04732μF. The same is true when inductively measurement. Extremely convenient.
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