One, pressing with a finger expresses what express with the number to choose:
1, watch of pressing with a finger is read take precision poorer, but the process that index swings is more intuitionistic, its swing speed range also can be mirrorred objectively quite sometimes the volume that is measured (measure television data bus line for instance (SDL) when deferent data slight shake) ; Digital watch reading is intuitionistic, but the process that the number changes looks very mixed and disorderly, watch not quite easily.
2, there are two batteries commonly inside watch of pressing with a finger, the 1.5V of a low voltage, it is the 9V of tall voltage or 15V together, its are black watch pen is to be being carried for pen of relatively red watch. Digital watch is commonly used the batteries of a 6V or 9V. In resistor archives, the electric current of the output that express a pen that pressing with a finger expresses wants for relative number watch a lot of bigger, with R × 1 Ω archives can make loudhailer gives out canorous " Da " sound, can illume even with archives of Ω of R × 10k glow diode (LED) .
3, in voltage archives, watch of pressing with a finger is compared for watch of word of logarithm of internal resistance photograph small, measure precision photograph to compare difference. The circumstance of small electric current of certain tall voltage cannot be measured even accurate, because its internal resistance is met,to be being measured circuit causes an effect (in the acceleration that measures television picture tube for instance the measured value when class voltage is met a lot of lower than real value) . The internal resistance of archives of digital watch voltage is very great, be in million Europe at least class, to be being measured circuit is affected very small. But the influence that extremely tall output impedance makes its get inductive tension easily, in interference of a few electromagnetism stronger circumstance measures the data that give may be empty.
4, anyhow, in opposite for the imitate circuit of tall voltage of big electric current is measured in applicable finger watch, for instance result of television, acoustics is put. In the digital circuit of low voltage small electric current in measuring, applicable number is expressed, for instance BP machine, mobile phone. Not be absolutely, can choose watch of pressing with a finger and digital watch according to the circumstance.
2, measure skill (if do not make a specification, show those who use is watch of pressing with a finger) :
1, measure mike of the horn, earphone, type that use a group: With R × 1 Ω archives, either expresses a pen to receive one aspect of the matter, point of another watch pen hits another end, normal when can give out ringing noise to measure " Da " sound. If do not ring, it is coil was broken, if small and noise is pointed, it is to have the problem that brush a circle, also cannot use.
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