Saturday, January 1, 2011

【 Weak current College 】 digital multimeter with summaries and tips 】


A measurement of the voltage
1, DC voltage measurements, such as batteries, Walkman power, etc. First of all, the black table pen into the "com" hole, red table pen into "V Ω." The knob selected to estimate a large measuring range (Note: dial values are maximum range, the "V-" indicates that the DC voltage V ~, "said AC voltage rail," A "is the current file), then the table amount of power or battery ends; maintain contact with stability. Values can be read directly from the screen, if it is displayed as "1." , Then the range is too small, you'll increase the range and measurement. If the value left "-" indicates that the table amount of polarity and actual power polar opposite, at which point the red table amount received is the anode.
2. AC voltage measurements. Table pen Jack and DC voltage measurements, but should be turned into the AC outlets "V-" premises required range. AC voltage and positive and negative, are the same as with the previous measurements. Whether measuring AC or DC voltage, should pay attention to security of the person, don't just hand touch the metal parts of the table amount.
Second, current measurement
1, DC current measurement. First black table pen insert "COM" in the hole. If the current measuring more than 200mA, you want to insert the red table pen "10A" Jack and the knob to DC 10A "stalls"; If the current measuring less than 200mA, red table pen insert "200mA" Jack, knob to DC 200mA within the appropriate range. Adjust, you can measure. The multimeter series into the circuit, you can read remained stable. If it is displayed as "1." , Increase range; if the value "-" on the left appears, it indicates that the current from the black table pen into the multimeter.
Measurement of AC current. The same measurement methods and 1, but stalls should hit exchanges stalls, current measurement should be red after the pen back to "V" hole, if Ω forget this step directly measuring voltage, haha! your table or power will be "a ray of smoke in the sky"-scrap!
3. resistance measurement
The table amount into the "COM" and "V" holes, Ω knob to "fight" Ω in the range, use the table amount received in the resistance ends of metal parts, the measurement can be hand contact resistance, but do not handle at both ends, so contact resistance can affect measurement precision-the human body is a large but limited resistance of conductor. Readings, to keep the table amount and resistance are good contact; Note: the "200" stalls are "Ω," "2K" to "200K" stalls units as "K Ω," and "the unit" above 2M is "M Ω."
IV. diode measurements
Digital Multimeters to measure light-emitting diode, rectifier diode ... Measurement, table pen position and voltage measurement, the knob to "" stalls; red table amount of cathode diode, the black table amount received as negative, then displays the diode forward voltage drop. Schottky Diode pressure drop is about ordinary 0.2V Silicon rectifier tubes (1N4000, 1N5400 series, etc.) about 0.7V, led about 1.8 ~ 2.3V. Change the table amount, the display shows "1." It is normal, because the diode reverse resistance is very large, otherwise this tube has been penetrated.
Measurement of five, transistor
Table pen-ibid; its tenets of diodes. First assume that A foot to the base table, with black pen and touch the feet, the red table pens and other contacts with the other two legs feet respectively; if two readings are 0.7V around, and then received A red, black pen contact the other two legs, if show "1", A foot to base, otherwise require measurement and this tube to PNP. The collector and emitter how can I tell? digital table cannot be used as a table like pointer pointer-to-rail, what should we do? we can use the "hFE" stalls to judge: first stalls hit "hFE" stalls, you can see the stall next to a row of small Jack, divided into PNP and NPN tube measurements. As already determine pipe, base insert corresponding hose "b" in the hole, and the remaining two feet respectively insert "c", "e" in the hole, you can read values, i.e. values; then β fixed base, the other two feet transposes two readings; compare, reading larger pin position and the surface of the "c", "e".
Tips: you can only directly on a method such as the 9000 series of small tube measurements, to measurement of large pipe, you can use connection method, which uses small conductor will lead three pins. This facilitates a lot of Oh.
6 MOS FET's measurement
N channel have made 3D01, 4D01, Nissan's 3SK series. G-pole (grid): use multimeter diode stalls. If a PIN and the other two foot pressure drop between the positive and negative are greater than 2V, i.e. display "1", the foot is the gate G. Then exchange table amount for the remaining two foot measurement, pressure drop small at that time, the black table amount received is D pole (drain), red table amount received is very S (source).
1: voltage
In testing or production, can be used to measure the PIN voltage devices, and the normal voltage comparison can be drawn for damage. Can also be used to detect voltage value smaller Zener diode voltage values, its principle figure: R $ 1K, power-end voltage depending on voltage tube of nominal voltage values, than the nominal voltage greater than 3V, but do not exceed the 15V. Then use multimeter test D tube voltage value, this value is the actual voltage value D pipe.
Second, the current gear
String table into the circuit, the current is measured and monitored, if current far deviates from normal (thumb or original normal parameter), if necessary, adjust the circuit or needs maintenance. You can also use the table of measuring battery 20A rail short circuit current, upcoming and two table pen directly connected to the battery at both ends. Remember that time never exceeds 1 second! note: this method only applies to batteries, 5, 7, rechargeable battery, and beginners should have familiarity with maintenance personnel, must not, on its own actions can bebased on the short circuit current! determine battery performance, in the full power of the same type of battery, short circuit powerFlow better.
3. resistance stalls;
Can be used to determine the resistance, diodes, transistors and bad way. For resistance to its practical resistance deviation from the nominal value when you have too much damage. For the second transistor, two feet of resistance are not as big a value (a few hundred K and above), you can view performance degradation or breakdown damaged, note this transistor is without resistance. This method can also be used for manifold block, to be clear: manifold measurement only and normal parameters for comparison.
4. now ordinary table pen multimeter exists resistance is large, interested enthusiasts can produce a secondary tables pen; method: prepare a high-quality speaker meters line or multi-core copper wire with insulation of clip a pair (red and black) for speaker wiring of banana plug a pair (red and black); line end welding in jail in the clip on the other end of the corresponding access banana plug; a pair of fine table pens that you're done.

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