1. Funkcija
In papildymas to the penkios funkcijos iš matavimas AC ir DC įtampa, AC ir DC current, and resistance, the digital multimeter also has digital calculation, reading hold, error readout, diode detection, word length selection, IEEE-488} interface or RS-232 interface and other functions should be selected pagal to specific requirements.
2. Diapazonas ir diapazonas
DMMs come in many ranges, but the basic range is the most accurate. Many digital multimeters have automatic range function, no need to manually the range, making the measurement convenient, accurate and fast. There are well many digital multimeters with over-range capability. When the measured value exceeds the range but has not reached the maximum display, it is not necessary to change the range, thereby improving the tikslumas ir skiriamoji geba.
3. Accuracy
The maximum error allowed by the digital multimeter depends not only on its variable error, but also on its fixed error. When choosing, it depends on how much the stability error and linearity error are, and whether the resolution meet the requirements. If the general digital multimeter requires {{{{{}}}}}{}0{{1{{10}}}5 to 0.002, at least 61 digits should be displayed; 0.005 to 0.01, at least 51 digits should be displayed; 0.02 to 0.05, at least 41 digits should be displayed; 0.1 Below, at least 31 digits should be displayed.
4. Įvestis varža ir nulis srovė
If the input resistance of the digital multimeter is too low and the zero current is too high, it will cause measurement error. The key depends on the limit value allowed by the measurement device, that is, the internal resistance of the signal source. When the signal source impedance is high, an instrument with high input impedance and low zero current should selected so that its influence can be ignored.
5. Serija režimas atmetimas santykis ir bendras režimas atmetimas santykis
In the presence of įvairių trikdžių tokių kaip elektrinių laukų, magnetinių laukų ir įvairių aukšto dažnio triukšmų arba ilgo nuotolio matavimų, it is easy to mix in interference signalai ir priežastis netikslūs rodmenys. Todėl, instrumentai su aukšta styga ir common-mode atmetimas santykiai turėtų būti pasirinkta pagal to the use environment, ypač Kai performansas didelis tikslumas matavimas, tu turėtum pasirinkti a skaitmeninis multimetras su a apsauga terminalas G, kuris gali gerai slopinti common-mode interferencija.
6. Ekranas forma maitinimas tiekimas
The display form of the digital multimeter is different from numbers, and it can also display charts, text and symbols, so as to facilitate on-site observation, operation and management. According to the dimensions of its display devices, it can be divided into four categories: small, medium, large and super large.
The power supply of the digital multimeter is generally 220V, and some new digital multimeters have a wide range of power supply, which can be between 1100V and 240V. Some small digital multimeters can be used with batteries, and some digital multimeters can be used in three forms: alternating current, internal nickel-cadmium batteries or external batteries.
