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Analysis Theory and Application of Analog Multimeter

In Electronic Infomation Category: A | on April 23,2011


"Meter" is the abbreviation of the multimeter, which is an indispensable electronic production tools. Multimeter to measure current, voltage, resistance, and LA1810 datasheet and some amplification transistor can be measured, frequency, capacitance, logic potential, decibels and LA1810 price and so on. There are many multimeter, and LA1810 suppliers and now the most popular mechanical pointer and digital multimeter, they have their advantages. For e-beginners, we recommend using Analog Multimeter, because we are familiar with some of its principles of e-knowledge helpful. Here we introduce some machinery Analog Multimeter principle and use.

The basic principles of meter

Multimeter is to use a basic principle of magnetic sensitive DC current meter (microammeter) to do the header. When the small current through the meter, there will be current instructions. However, high-current header can not, therefore, must be parallel and serial number of the table head shunt resistor or a buck, which measure the current in the circuit, voltage and resistance. In the following we will be briefed.

DC current measurement principle

Shown in Figure 1a, in the form of an appropriate resistor in parallel head (called a shunt resistor) to shunt can be extended current range. Change the shunt resistor, you can change the current measurement range.

Principle of measuring DC voltage

Shown in Figure 1b, at the head table of an appropriate resistor in series (called the double resistance) for step-down can be extended voltage range. Change the multiplier resistor, you can change the voltage range.

AC voltage measurement principle

Shown in Figure 1c, as the table header is DC, so the measurement of exchanges, the need to install one and, string-type half-wave rectifier circuit, the AC is rectified into DC and then head through the table, so you can According to DC to measure the size of AC voltage. AC voltage range extension method similar to the DC voltage range.

Resistor principle

Shown in Figure 1d, head of the table appropriate resistor in parallel and series, while series with a battery, so that current through the resistor under test, according to the current size, we can measure the resistance. Change the shunt resistor, you can change the resistance of the range.

Multimeter use

Multimeter (to 105 for example) as shown on the dial. Through the switch knob to change the measurement items and measurement range. Machinery used to maintain the zero knob at the left pointer still zero. Zero when the knob is used to measure the resistance of the right to zero the pointer aligned to ensure the accuracy of measured values.

Meter measurement range is as follows:

DC voltage: min 5-speed-0-6V; 0-30V; 0-150V; 0-300V; 0-600V.

AC voltage: min 5-speed-0-6V; 0-30V; 0-150V; 0-300V; 0-600V

DC current: min 3 file-0-3mA; 0-30mA; 0-300mA.

Resistance: min 5-speed-R * 1; R * 10; R * 100; R * 1K; R * 10K

Measuring Resistance

First ride with the short stick form, so that deflection of the pointer to the right turn, then adjust the zero knob, so that just means the pointer to 0. Then the two rods were exposed to measured resistance table (or circuit) at both ends, read the scale pointer ohm line (first line) on the readings, and then multiplied by the number of the target file is the measured resistance value. For example with R * 100 block measuring resistance, the pointer means 80, is the measured resistance value of 80 * 100 = 8K. As the "?" Tick left part of the reading dense and difficult sights, so the measure should be to select the appropriate Ohm file. Tick ??the pointer in the middle or right side, so that relatively clear and accurate readings. Every shift, bar table should be re-short the two re-adjust the pointer to zero in order to test standard.

Measuring DC voltage

First estimate of the size of the measured voltage, and then switch to the appropriate V-allocated range, the rod is then measured voltage table "" side, the negative voltage to be measured then the table bar "-" side. Then the block number with standard DC-range symbol "DC-" scale line (second line) on the number pointer to read out the measured voltage. As measured by V300 V file, the instructions can be directly read 0-300 number. As measured by V30 V file, only to scale a line 300 to remove the figure "0", as is 30, and then turn to such figures as 20,10 200,100 can read pointer indicates the value of direct . For example, files with the V6-volt DC voltage measurement, the pointer means 15, then the measured voltage of 1.5 volts.

Measuring DC current

First estimate the size of the measured current, and then switch to the appropriate conversion mA range, then the multimeter in series in the circuit, as shown. DC signs were also observed marked "DC" scale line, such as the current selection in the 3mA range profile, then, should the number of the surface of the scale line 300, remove the two "0", as 3, then turn to 200 , 100 as 2,1, so that you can read the measured current value. For example, a DC 3mA range measuring DC current, pointer 100, the current is 1mA.

Measuring AC voltage

AC voltage measurement methods and measuring DC voltage similar, the difference is not due to alternating positive and negative of the points, so the measurement of exchanges, the table also do not need sub-rod positive and negative. Reading method for the measurement of DC voltage with the above method, like reading, but figures should see the exchange symbol marked "AC" position of the scale pointer line.

Multimeter Notes

Multimeter is more sophisticated equipment, if used improperly, not only result in inaccurate measurements and easily damaged. However, as long as we master the use of meter and cautions, caution, then the meter can be durable. Use the multimeter should pay attention to the following matters:

1, measuring current and voltage can not spin the wrong gear. If you mistakenly resistance profile to measure voltage or current file to easily burn out the meter. Multimeter not, it is best to stall the most high-end spin to the AC voltage to avoid damage due to improper use.

2, measuring DC voltage and DC current, pay attention to "" "-" polarity, do not get wrong. Pointer reversal is found open, both tables should be immediate replacement bars, to avoid damage to the pointer and the header.

3, if you do not know the size of the measured voltage or current, should be the most high-end, and then choose the appropriate gear to test, so as not to damage Biaozhen header deflected over. Chosen close to the measured value of more stalls, the more accurate measurement of the value.

4, measure the resistance, do not hand touched the naked ends of components (or two sheet metal parts stick), so that the body resistance and measured resistance in parallel, the measurement results are not accurate.

5, measurement of resistance, such as the two shorting bar table, adjusting the "zero ohm" knob to the maximum, the pointer still fall short of 0:00, this phenomenon is usually due to inadequate battery voltage table, and should be Replace with new batteries before being accurately measured.

6, multimeter do not, do not spin in the resistance profile, as in a battery, such as accidentally touching easy to make two short stick form, not only consuming the battery, even when serious damage to the meter.

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