![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
Multimeters are also called multimeters, multimeters, and multiplexers. They are multi-functional and multi-range measuring instruments. General multimeter can measure DC current, DC voltage, AC voltage, resistance and audio level, etc. Some can also measure AC current, capacitance, inductance and some semiconductor parameters (such as β).
1. The structure of the multimeter (taking the 500 model as an example)
The multimeter is composed of three main parts: the meter head, measuring circuit and transfer switch.
(1) Meter head: It is a high-sensitivity magnetoelectric DC ammeter. The main performance indexes of the multimeter basically depend on the performance of the meter head. The sensitivity of the meter head refers to the value of the DC current flowing through the meter head when the meter pointer deflects at full scale. The smaller the value, the higher the meter head sensitivity. The greater the internal resistance when measuring voltage, the better its performance. There are four tick marks on the meter head, and their functions are as follows: the bar (from top to bottom) is marked with R or Ω, indicating the resistance value, and the scale switch is read when the transfer switch is in the ohmic range. The second line is marked with ∽ and VA, indicating the AC, DC voltage and DC current values. When the transfer switch is in the AC, DC voltage or DC current block, and the range is other than AC 10V, the scale line. The third one is marked with 10V, which indicates the AC voltage value of 10V. When the transfer switch is in the AC and DC voltage blocks and the range is in the AC 10V, this scale line is read. The fourth bar is marked with dB and indicates the audio level.
(2) Measuring circuit
The measuring circuit is a circuit used to convert all kinds of measured to small DC current suitable for meter measurement. It is composed of resistance, semiconductor components and batteries
It can convert a variety of different measured (such as current, voltage, resistance, etc.), different ranges, after a series of processing (such as rectification, shunt, voltage division, etc.) into a certain amount of tiny DC current The meter is measured.
(3) Transfer switch
Its role is to select a variety of different measurement circuits to meet the measurement requirements of different types and different ranges. There are generally two transfer switches, each marked with a different gear and range.
2. Symbol meaning
(1) ∽ means AC and DC
(2) V-2.5KV 4000Ω / V means that for AC voltage and 2.5KV DC voltage block, the sensitivity is 4000Ω / V
(3) AV-Ω means measurable current, voltage and resistance
(4) 45-65-1000Hz indicates that the frequency range of use is below 1000 Hz, and the standard power frequency range is 45-65Hz
(5) 2000Ω / V DC means the sensitivity of the DC block is 2000Ω / V
3. Use of multimeter
(1) Familiar with the meaning of the symbols on the dial and the main functions of the knobs and selector switches.
(2) Perform mechanical zero adjustment.
(3) According to the type and size of the measurement, select the gear and range of the transfer switch to find the corresponding scale line.
(4) Select the position of the test lead jack.
(5) Measuring voltage: when measuring voltage (or current), you must select a good range. If you use a small range to measure a large voltage, there is a danger of burning the meter; if you use a large range to measure a small voltage, the pointer deflection is too small. Unable to read. The selection of the range should try to deflect the pointer to about 2/3 of full scale. If you do not know the magnitude of the measured voltage in advance, you should first select the gao range block, and then gradually reduce to the appropriate range.
a. Measurement of AC voltage: Put one switch of the multimeter on the AC and DC voltage blocks, and the other switch on the appropriate range of the AC voltage. The two test leads of the multimeter can be connected in parallel with the circuit or load under test.
b. Measurement of DC voltage: Put one changeover switch of the multimeter on the AC and DC voltage blocks, and the other changeover switch on the appropriate range of the DC voltage, and connect the "+" test lead (red test lead) to the high potential, "- When the test lead (black test lead) is connected to a low potential, the current flows from the "+" test lead and out of the "-" test lead. If the test leads are connected reversely, the pointer of the meter will deflect in the opposite direction, and it is easy to bend the pointer.
(6) Measuring current: When measuring DC current, put one switch of the multimeter in the DC current block and the other switch on the appropriate range of 50uA to 500mA. The current range selection and reading method are the same as the voltage. When measuring, you must first disconnect the circuit, and then connect the multimeter to the circuit under test in accordance with the direction of the current from "+" to "-", that is, the current flows in from the red meter pen and flows out from the black meter pen. If the multimeter is connected in parallel with the load by mistake, the internal resistance of the meter head is very small, which will cause a short circuit to burn the meter. The reading method is as follows:
Actual value = indicated value × range / full deviation
(7) Resistance measurement: When measuring resistance with a multimeter, the following methods should be used:
a Choose the appropriate override block. The scale line of the multimeter ohm block is not uniform, so the selection of the multiplier block should make the pointer stay at the thinner part of the scale line, and the closer the pointer is to the middle of the scale, the more accurate the reading. In general, the pointer should be between 1/3 and 2/3 of the scale.
b Ohm zero adjustment. Before measuring the resistance, short the two test leads and adjust the "ohmic (electrical) zero adjustment knob" at the same time, so that the pointer just points to the zero position on the right side of the ohm scale. If the pointer cannot be adjusted to zero, it means that the battery voltage is insufficient or there is a problem in the instrument. And every time the magnification gear is changed, the ohm zero must be adjusted again to ensure accurate measurement.
c reading: the reading of the meter is multiplied by the magnification, which is the resistance value of the measured resistance.
(8) Precautions
a When measuring current and voltage, the range cannot be changed while electrified
b. When selecting the range, select the large one first and then the small one. Try to make the measured value close to the range
c When measuring resistance, it cannot be charged. Because when measuring resistance, the multimeter is powered by an internal battery. If the measurement is live, it is equivalent to connecting an additional power supply, which may damage the meter head.
d. After use, the change-over switch should be in the high gear or neutral gear of AC voltage.
4. Digital multimeter
Now, digital measuring instruments have become mainstream, and there is a trend to replace analog instruments. Compared with analog instruments, digital instruments have high sensitivity, high accuracy, clear display, strong overload capacity, easy to carry, and simpler to use. The following uses VC9802 digital multimeter as an example to briefly introduce its usage and precautions.
(1) How to use
a Before using, you should carefully read the relevant operating instructions, familiar with the role of power switch, range switch, jack, special socket.
b Put the power switch to the ON position.
c. Measurement of AC and DC voltage: Set the range switch to the appropriate range of DCV (DC) or ACV (AC) as required. Insert the red test lead into the V / Ω hole and the black test lead into the COM hole, and connect the test lead and the tested circuit in parallel. The reading is displayed.
d. AC and DC current measurement: set the range switch to the appropriate range of DCA (DC) or ACA (AC), the red test lead is inserted into the mA hole (<200mA) or 10A hole (> 200mA), and the black test pen is inserted into the COM hole And the multimeter can be connected in series in the circuit under test. When measuring DC, the digital multimeter can automatically display the polarity.
e Resistance measurement: Set the range switch to the appropriate range of Ω, insert the red test lead into the V / Ω hole, and insert the black test lead into the COM hole. If the measured resistance value exceeds the large value of the selected range, the multimeter will display "1", and a higher range should be selected at this time. When measuring resistance, the red test lead is positive and the black test lead is negative, which is the opposite of a pointer multimeter. Therefore, when measuring polar components such as transistors and electrolytic capacitors, you must pay attention to the polarity of the test leads.
(2). Precautions for use
a. If the size of the measured voltage or current cannot be estimated in advance, you should first dial the gao range block to measure once, and then gradually reduce the range to an appropriate position as appropriate. After the measurement, the range switch should be set to the gao voltage block, and the power should be turned off.
b At full scale, the meter only displays the digit "1" in the upper digit, and all other digits disappear. In this case, the higher scale should be selected.
c When measuring the voltage, the digital multimeter should be connected in parallel with the circuit under test. When measuring current, it should be connected in series with the circuit under test. When measuring DC, it is not necessary to consider the positive and negative polarities.
d When the AC voltage block is used to measure the DC voltage, or the DC voltage block is used to measure the AC voltage, the display will show "000", or the number on the lower digit will jump.
e. It is forbidden to change the range when measuring high voltage (above 220V) or large current (above 0.) to prevent arcing and burning the switch contacts.
f When "", "BATT" or "LOW BAT" is displayed, it means that the battery voltage is lower than the operating voltage.
The utility model discloses a Kitchen Shower head that is convenient to switch the water outlet mode, has a compact structure, and is easy to use, and a kitchen faucet using the kitchen shower head. , The shower head is provided with a water separator, and the water separator is provided with an annular flow channel and an inner flow channel respectively connected to the spray water outlet body and the V-shaped water outlet body, and the lower end of the outer wall of the water separator is upwardly circular A plurality of water inlet holes connected to the annular flow channel are provided, and a first sealing ring is provided on the lower side of the water inlet hole; the water outlet end of the shower body is connected with a converter, and the converter is provided with a communicating In the water diversion cavity at the water outlet end of the shower body, the lower end of the water diversion device is installed in the water diversion cavity and can move up and down, and the upper end of the inner wall of the water diversion cavity is provided with a convex ring matching the first sealing ring, so The bottom surface of the water diversion cavity is provided with a sealing gasket that can seal the inner flow channel.
Waterfall Shower Head,Overhead Shower Head,Push Button Hand Shower,Brushed Nickel Sink Faucet
Yuyao Zelin Sanitary Ware Co., Ltd , https://www.kitchen-sinkfaucet.com