1. In measuring the voltage, is it possible to use the 3V range and 300V range? Why? Expalin.?

Question

2. what are the precautions to be taken in measuring voltage, current and resistance.?

3. which resistance is in the center of the ohm scale Rx1?

Answer 1

I think something is missing in question 1, I'm not sure what they mean.  I'll guess though, that they mean an analog meter.

For question 1, if you set the meter on 3V and measure higher than 3 volts, the needle will pin to the right.  It is unlikely that any modern meter will be damaged, however, there is usually overcurrent protection.  However, you will be unable to read what the voltage really is.  If you measure something on the 300V range, and it's really just 1.2 volts, the needle will barely deflect, and you won't be able to get as accurate a reading as you would on the 3V range.

Question 2, NEVER attempt to measure voltage with the meter set on current.  That will short out the voltage source.  If it is a high power circuit you are measuring, you will possibly blow out the meter or injure yourself.  Don't touch the wires you're measuring with your hands.  Slightly less dangerous is measuring voltage with the meter set to resistance, or AC with the meter set to DC, or having the polarity of the leads reversed.  It's also not a good idea to measure the resistance of something in a powered circuit - that could hurt the meter.  Measuring the resistance of something in a circuit, even powered off, could result in an incorrect reading.

Question 3, I have no idea.

Answer 2

1...yes...as long as you are within the ranges you select..under 3v you wont read..over 300v you could damage your meter..make sure you are on either AC volts or DC volts..most household ckts are 110v and/or 220v

2...voltage you must read in parallel...current is read in series...ohms is read in parallel with no electricity on the ckt..

3...i'm not sure what you mean..

4..are you using an analog or digital meter

Answer 3

1.  Yes you can use either one. However to obtain the most accurate measurements the 3v range is used to measure voltages from 0 to 3 volts.  Three volts causes full scale deflection. The 300v range is used to measure voltages from 3v to 300v. Three hundred volts causes full scale deflection. On the 300v range setting low voltage measurements are not very accurate especially below 3 volts. This is why the 0 to 3v range position was added to your multimeter.

I don`t know if you meant safety precautions or precautions to ensure more accurate measurements so I will throw in a few of both.

2.  For voltage measurements the power must be on therefore you must be carefull not to touch any of the test points or open circuitry with any thing other than a test probe.

For current measurements made with a multimeter you must turn the power off, break the circuit you wish to test, discharge all the capacitors in the circuit you are testing, connect the test probes across the break in the circuit, turn the power back on and make your measurement

For resistance measurements make sure power is off and all capacitors in the circuit are discharged. Remove one terminal of the resistor from the circuit to insure that you are not measuring through some other component that is remotely connected in parallel with the resistor you wish to test

3.  The instruction mamual for your multimeter should tell you what the full scale deflection reading is in ohms with the position switch in the Rx1 position. Locate the ohm scale on the multimeter that has this reading on it. The center scale reading is not necessarily half the full scale reading so you will have to see what it reads at the center of the scale.

Answer 4

1. yes, it is possible to use any of the ranges, that is what they are there for.

2. Current, insert the meter is series. Resistance, remove all power from the circuit.

3. I don't know, they are all different. Look at it.

Answer 5

You can use both of it.Ä°f you are measuring 3 volts ( if the system A.C , D.C. selected correctly ) you can use 300 v range for both of it.( sensitivity ?)When you are measuring do not touch anything except the probes of the meter. ( this is the safety guide ).Even if you are measuring resistance without voltage or current if you touch the resistance the value changes.These are all for information.The main point of measuring is if you have not any idea which range you are measuring, start from the largest scale  like R x 1M or 1000 V or 10 A ( the largest scales of the multimeter) the largest scale differs for different manufacturers.But for a sensitive measurement ( for analog meters you  must be between 3-4th quarter of the scale) than you have a bigger chance to have a correct measurement.This means if you are measuring 3 V  and if you are on a measuring scale for 5 V  you will measure more correct according to scale for 10 V.If you are measuring 300 volts and if you are on  500 V scale you will  measure more correctly if you do your measurement at 1000 V you will be making measuring mistakes.Another thing if you are trying to measure 300V at 3 V scale ????? The multimeter is burnt ot damaged because of high voltage.