Digital multímetro emergencia online resistencia medición
Uso a digital multímetro para medir en línea resistencia en una emergencia El siguiente puntos debería ser prestado atención cuando usar la carga caída voltaje medición método :
(1) Diferentes tipos de digital multímetros tener diferente escala-completa prueba voltajes y circuito-abierto voltajes, so el valor rango de del carga resistencia R1 debería ser determinado por experimentos.
(2) durante funcionamiento, el cargador resistencia R1 debería estar conectado entre el digital multímetro V/Ω and the COM jack first, and the online resistance measurement can only be perform after the digital mulmeter reads the measured value of R1 at this resistance barrera. It is not possible to connect the circuit under test first and then connect the resistor R1 in parallel. Esto causará el silicio tubo en el circuito bajo prueba a girar en debido a el alto prueba voltaje bloqueado por el digital multímetro (grande medición error será generado). Por lo tanto, esto orden no puede ser invertido.
(3) Since the resistors connected in parallel with the emitter junction and collector junction of transistors in general circuits are mostly kΩ to hundreds of kΩ, but rarely tens of ohms, the digital multimeter is usually set in the middle to block , that is, the 200kΩ block (the resolution of this block is 0.1kΩ) or the 20kΩ block. If R=R1 is measured. If RX/(R1 plus RX) is 0 or very small, it means that the circuit under test has a short-circuit fault (RX=0) or the range is too high. At this time, it should be carefully measured with low resistance (2kΩ block). If R=R1 is measured. RX/(R1 plus RX) is very close to R1, which means that the circuit under test may have an open circuit fault (RX=∞) or the range is too low, and it should be retested with high resistance (2WΩ block).
(4) 200Ω electric block and 20MΩ block are rarely used for online measurement. Because the load resistance R1 is connected in parallel with the measured resistance RX, the measurement range of electrical resistance has actually been expanded, and the ability to measure high resistance has been improved, so it is generally enough to use a 2MΩ block. In addition, since the resolution of the 2kΩ block is 1Ω, it is enough to use this block to judge whether there is a short-circuit breakdown of the online transistor without the circuit. In general, not only three loading resistors can meet the needs of measuring online resistance. Take the DT830A digital multimeter as an example, for the 2kΩ block, R1=R0=1kΩ, for the 200kΩ block, R1=0.47RO=47kΩ, for the 2MΩ block, R1=0.47R0=470kΩ. Of course, we can also use a 470kΩ potentiometer instead of the above three loading resistors.
(5) After mide the online resistance, do not forget to remove the loading resistor R1 connected between the digital mulmeter V/Ω and the COM jack in time to avoid affecting the normal use of the mulmeter and accidents (when misuring high voltage).
