2 , multimeter usage and attention points

( 1 ) When measuring DC voltage, resistance should be noted that the multimeter . Multimeter resistance, in the lower left corner of the header of the dial has the following flags : 20kω/vdc is used when the dc block , per volt of 20kω; When 10kω/vdc to hand dc block , per volt of 10kω. So for 20kω/vdc occasions , the measurement block : 1000 volts 20mω; 250 volt block of 5mω; 50 volt block of 1mω; 10 volt block of 200kω; 2.5 volt block of 50kω. There as calculated above resistance at both ends of the test bar , so there will be errors when measuring . Such as detecting oscillation circuit and the burst of color television sets high impedance circuit is a circuit should be measured with a high range, to avoid affecting the internal resistance of the multimeter to the circuit under test . However, the internal resistance of the multimeter can also be used as a resistor can be disconnected easily confirm defective parts . In addition to the low pressure circuit and a high voltage resistance of the circuit , the resistance circuit breaking line as the oscillation circuit can be used to replace the internal resistance of the multimeter , the symptoms of the screen to see whether it has changed.

( 2 ) the use of the AC line voltage output circuit block in order to determine the presence or absence of the signal and the synchronization signal can be used to block the exchange multimeter , test rod string on its access to about 0.1 ~ 0.2μf capacitors , DC blocking and only measure AC section. Multimeter instructions are carried out using a sine wave RMS scale , because the signal waveform of each part of the majority of non- sine wave, so the peak multimeter instructions than observed with an oscilloscope , etc. - the peak is low, but you can easily determine the test points if a signal . AC measurement measurement block , the video signal is a video detector stage about 2 to about 5 volts ; synchronizing signal synchronizing circuit 3 to about 5 volts ; excitation square wave output line is about 15 to 25 volts. ( 3 ) the use of the current block. Current with a multimeter block both ends of the kinescope cathode resistor connected to the meter , the current value can be judged from the picture tube aging.

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