can somebody teach me how to measure the output current by correct method?
why cannot use the multimeter to measure the output current directly?
is need to place a shunt resistor by series method then measure it??
Multimeters have an incredibly high input impedance. If you connect your meter directly to the output of your circuit and ground you will be loading your circuit with this high impedance. If you put a shunt resitor on the output and measure the volt drop across that resistor then by ohms law you can calculate the output current.
Multimeters have an incredibly high input impedance. If you connect your meter directly to the output of your circuit and ground you will be loading your circuit with this high impedance. If you put a shunt resitor on the output and measure the volt drop across that resistor then by ohms law you can calculate the output current.
Since you have to ask this question i assume your a beginner.
Voltage is measured in parallel
Current is measured in series.
To measure the volt drop place the probes acros either end of the resistor, taking care to get the polarity right or you will get a negative answer.
You may want to buy a book for beginners which illustrates all the basics, i believe there are lots of tutorials on the internet if you do a search on google.
Hope it helps, others may be able to give you their experiences.
current is measured in series . put the multimeter in current measurement mode , and connect it in series .
if yoy have a voltmeter instead of multimeter , use a low value (ref : the power dissipation in the resistor) shunt resistor and measure the voltage ACROSS the shunt resistor
Remember if your going to use this method make sure you select the correct range (200mA or 10A) for your application. If you dont know what currents are flowing use the 10A as a safety net.
Ive blown a fair few fuses in my time but my meter still lives....just
Remember if your going to use this method make sure you select the correct range (200mA or 10A) for your application. If you dont know what currents are flowing use the 10A as a safety net.
Ive blown a fair few fuses in my time but my meter still lives....just
so,if i wan to measure the mobile phone (nokia, label 3.7VDC 350mA) charger's output current & voltage, how can i measure it??
my lecturer always teach me to measure the current , must place the resistor front of the multimeter by series method, is it correct method??
You should measure the voltage with the charger powering the phone. The voltage will read too high without a load.
You should measure the current of the charger connected to the phone when the phone is turned on. You probably just shorted the charger with the ammeter.
If you connected everything correctly, then your meters are very wrong.
You should measure the voltage with the charger powering the phone. The voltage will read too high without a load.
You should measure the current of the charger connected to the phone when the phone is turned on. You probably just shorted the charger with the ammeter.
If you connected everything correctly, then your meters are very wrong.
so, if i wan to design a cell phone charger connected by DC power ( for example connected by solar panel ), wat output current & voltage i suitable to use under the no load charger( cell phone no connect to charger)??
it depends...
on battery type, on battery capacity, on charge time you want.
it depends on how much of the charing chircuit is in the phone.
it depends if there is temperature sensor
You can't design a charger from no load spec's. You need to know the charging voltage and current of the battery, the operating voltage and current of the phone and the solar panel's max output and average output voltages and currents.
You can't design a charger from no load spec's. You need to know the charging voltage and current of the battery, the operating voltage and current of the phone and the solar panel's max output and average output voltages and currents.
solar panel max voltage is 5.4v,current is around 300mA
& load wat i need to charge is cell phone, voltage is 3.7v-5.4v,350mA-500mA
so, wat i need to do or know next step?? thx ur helping & teaching
Oh no, certainly not a teacher. He is a lecturer so "miaomiaooh" is in university or college for sure. Lecturer don't teach but ask you to look it up yourself, or as one user said, points you to this very forum.
my lecturer always teach me to measure the current , must place the resistor front of the multimeter by series method, is it correct method??