How to measure the current of a charge current meter with a multimeter
Use the multimeter to measure AC and DC current must be the multimeter current gear dial to, AC or DC gear, using series connection in the line for measurement.
For the pointer multimeter, its red pen needs to be connected to the positive pole of the charger output, the black pen is connected to the load of the appliance being charged. If the digital multimeter is used to measure the current in the charging line, its red pen, black pen even if the connection is reversed can also measure the value of AC or DC current in the line, just in front of the digital multimeter display there is a - (- negative sign).
For measuring relatively small AC or DC charging currents, you can dial the multimeter's current setting to the 500mA setting. If you measure more than 500mA charging current, you need to dial the pointer multimeter or digital multimeter to the pointer multimeter 5A stall (MF47 multimeter except for a few models of 10A stall, usually only 5A DC current stall), while the digital multimeter it has 10A or 20A AC or DC current stall.
Because I usually use the digital multimeter for the automatic change of gear, so only be able to use it to say, other digital multimeter just need to dial gear pointing to 20A place can be. At this time, the red pen into the 10th gear, the black pen is still poor in the original COM jack on it.
Here I do not know the questioner said the charger is a cell phone charger or battery charger. But no matter what charger, in order to measure the DC charging current in the line, it is necessary to have to break a charging cable (or elsewhere in the charging plug, the charging cable will be broken one, the multimeter's red pen, the black pen, respectively, in series on the circuit). At this time, the charger's input cord plug into the 220V power supply, observe the charger and the actual charging current of the load being charged.
If it is a cell phone charger, then you need to waste a charging wire, the multimeter DC current gear of the two pens measured in the line for measurement can be.
Hit the multimeter to the current gear, and first high and then low gear selection principle, series connection to the charger line to be measured.
Here it should be noted that the battery is generally used in constant voltage charging method for rapid charging, due to the charging voltage is unchanged, and the battery ends of the point is relatively low, the beginning of the charging current will be very large, battery ends with the increase in voltage, the charging current will be gradually reduced, so, different charging time periods measured charging current is not the same.
Lithium battery charging and battery charging has this big difference, in order to be able to protect the maximum efficiency of lithium batteries and protect the battery use time, generally can be divided into four stages of pre-charging, fast charging, top-up charging, trickle charging. Therefore, the charging current of any one stage will also be different.
There are clamp multimeter and ordinary multimeter, clamp is simple, set the table to the current file, put the measured wire single into the clamp circle, you can read the data, ordinary multimeter needs to be connected in series to the circuit, pay attention to the range of the table, beware of burnt out, this table can be measured current will not be very large, is not suitable for measuring high-current circuits.
With a multimeter in series into the charging circuit, cell phone charging gear fast charging DC2A, slow charging DC500mA. or buy a cell phone charging special test questions, you can simultaneously detect the charging voltage and the battery, dual-LED display, the price of 25 yuan or so, the input and output are USI3 interface.
In addition, you can also string a 1 ohm resistor in the circuit, and then directly measure the voltage at both ends of the resistor, the voltage value is the current value. Since inserting the resistor drops the overall current, the actual current will be slightly higher than the measured value. (讠=v/R，when R=1
R=1 when R=v).
Dial the multimeter in the range of the corresponding current, if you don't know it, try to use the highest range possible, usually the highest range of a multimeter is 10A or 20A, unplug that red wire and plug it in the special socket. One end of the charger is connected to the battery, the two pens of the multimeter is connected to the other end of the charger, and the other one is connected to the rest of the battery. It doesn't matter if it's a digital multimeter, but if it's a pointer multimeter, be sure to pay attention to the polarity, the red pen must be connected to the positive terminal of the charger or the negative terminal of the battery, and the black pen must be connected to the negative terminal of the charger or the positive terminal of the battery. It depends on which end you string into.
A typical 12V charger will not output more than 8A, a better one will output a lot of current. The multimeter pen wire is too thin for testing the charger output current in series. It is best to use a non-contact measuring instrument.
Multimeter on the current file (two grades, mA and A), in accordance with the instructions will be the red pen, black pen inserted into the hole, the multimeter dialed to the corresponding A gear, and then the red and black pens in series into the current loop can be measured.
