Very basic multimeter questions.

Discussion in 'Electronic Basics' started by Simon Bartlett, Dec 29, 2003.

  1. Hi group.

    I've always used a multimeter on a trial and error basis, till I get a
    reading that looks like what I should get. I think it's time now that I
    try and understand what's going on though. As such, I've composed a
    list of simple questions, the answers to which would be a great help to
    me.

    1. The fused connector is rated to 500v max, 200mA max. Does that mean
    500v at 200mA? If I want to check a circuit running 12v 1A, can I
    safely use the fused connector or do I have to use the un-fused
    connector?

    2. I was trying to measure a current on a circuit of 12v 1A. To be
    safe, I used the unfused (10A) connector. I couldn't get a reading of
    volts at all (perhaps I should have tried amps). Should the 10A
    connector give identical readings to the fused connector where the
    current is within the fused connector's range?

    3. The Volts DC selector scale has points at 200m, 2000m, 20, 200, 500.
    Does the m refer to milli as in 200 millivolts, 2000milivolts? Of not,
    what?

    4. The Amps DC selector scale has points at 200(funny u symbol), 20m,
    200m, 10. What is the funny u symbol? And again, does the m stand for
    milli?

    5. The transistor tester has NPN and PNP markings. By looking at a
    transistor, how do I know if it's a NPN or PNP?

    6. The transistor tester has letters around the circle, e E B c E e c
    b. What's the story there? How do you know which to use?

    If anyone has a good reference that will answer similar questions, that
    would be much appreciated. I had a look at some sites offering
    multimeter basics, but weren't quite basic enough :)
    Simon Bartlett, Dec 29, 2003
    #1
    1. Advertising

  2. On Tue, 30 Dec 2003 09:38:17 +1000, Simon Bartlett <> wrote:

    >Hi group.
    >
    >I've always used a multimeter on a trial and error basis, till I get a
    >reading that looks like what I should get. I think it's time now that I
    >try and understand what's going on though. As such, I've composed a
    >list of simple questions, the answers to which would be a great help to
    >me.
    >
    >1. The fused connector is rated to 500v max, 200mA max. Does that mean
    >500v at 200mA? If I want to check a circuit running 12v 1A, can I
    >safely use the fused connector or do I have to use the un-fused
    >connector?


    I don't know your meter, so can't answer this one (perhaps you should
    post these questions again, mentioning the make and model of your
    meter.)

    >
    >2. I was trying to measure a current on a circuit of 12v 1A. To be
    >safe, I used the unfused (10A) connector. I couldn't get a reading of
    >volts at all (perhaps I should have tried amps). Should the 10A
    >connector give identical readings to the fused connector where the
    >current is within the fused connector's range?


    To measure current, you must break the circuit, and insert the meter
    in the break, so the current flows through the meter - AND set the
    meter to read current.

    With the meters I've used, you have to move the read meter lead from
    the "Volts" socket to a socket labelled "Amps" or "mA". My meter has
    one socket labelled "10A", and another labelled "mA". The "mA" socket
    is used when measuring currents up to 200 mA, and the 10A socket is
    used for larger currents.

    To measure voltage, you put the red meter lead in the socket marked
    "Volts/Ohms" (or something like that), and connect the two leads to
    the two points in the circuit you want to measure between. You do not
    break into the circuit when measuring voltage.

    >
    >3. The Volts DC selector scale has points at 200m, 2000m, 20, 200, 500.
    >Does the m refer to milli as in 200 millivolts, 2000milivolts? Of not,
    >what?


    Yes - "m" is "milli", or .001
    >
    >4. The Amps DC selector scale has points at 200(funny u symbol), 20m,
    >200m, 10. What is the funny u symbol? And again, does the m stand for
    >milli?


    The funny "u" is a greek letter "mu", which is used to indicate
    "micro", or .000001

    >
    >5. The transistor tester has NPN and PNP markings. By looking at a
    >transistor, how do I know if it's a NPN or PNP?


    With North American transistors (part numbers starting with "2N"),
    there is no way, other than looking them up in a book (or on the web).
    I think European transistors may indicate the sex and application in
    the letter prefix.

    >
    >6. The transistor tester has letters around the circle, e E B c E e c
    >b. What's the story there? How do you know which to use?


    E, B, and C are the emitter, base and collector leads of a transitory.
    The manual for the meter should give you some indication of how to
    connect a transistor.
    >
    >If anyone has a good reference that will answer similar questions, that
    >would be much appreciated. I had a look at some sites offering
    >multimeter basics, but weren't quite basic enough :)


    --
    Peter Bennett, VE7CEI
    new newsgroup users info : http://vancouver-webpages.com/nnq
    GPS and NMEA info: http://vancouver-webpages.com/peter
    Vancouver Power Squadron: http://vancouver.powersquadron.ca
    Peter Bennett, Dec 30, 2003
    #2
    1. Advertising

  3. "Simon Bartlett" <> wrote in message
    news:...
    > Hi group.
    >
    > I've always used a multimeter on a trial and error basis, till I get a
    > reading that looks like what I should get. I think it's time now that I
    > try and understand what's going on though. As such, I've composed a
    > list of simple questions, the answers to which would be a great help to
    > me.
    >
    > 1. The fused connector is rated to 500v max, 200mA max. Does that mean
    > 500v at 200mA? If I want to check a circuit running 12v 1A, can I
    > safely use the fused connector or do I have to use the un-fused
    > connector?


    You will have to use the unfused connector. This is because your circuit is
    drawing 1A and the fused connector is rated at 200mA max. This rating is
    independent of the circuit voltage (as long as it is below 500V).


    > 2. I was trying to measure a current on a circuit of 12v 1A. To be
    > safe, I used the unfused (10A) connector. I couldn't get a reading of
    > volts at all (perhaps I should have tried amps). Should the 10A
    > connector give identical readings to the fused connector where the
    > current is within the fused connector's range?


    Usually the unfused connectors in a multimeter are used only for current
    measurement. If you want to measure voltage you should use the connector
    marked with "V" on the multimeter (usually the fused one). If measuring
    current, the 10A connector should be used for high currents, and the fused
    one for low currents. The 10A connector may in fact only work when the
    multimeter is set to the 10A range. For all other ranges use the fused
    connector.


    > 3. The Volts DC selector scale has points at 200m, 2000m, 20, 200, 500.
    > Does the m refer to milli as in 200 millivolts, 2000milivolts? Of not,
    > what?


    Yes, it means milli.


    > 4. The Amps DC selector scale has points at 200(funny u symbol), 20m,
    > 200m, 10. What is the funny u symbol? And again, does the m stand for
    > milli?


    The "u" symbol means micro (i.e., 200 microamperes). The "m" is as above.


    > 5. The transistor tester has NPN and PNP markings. By looking at a
    > transistor, how do I know if it's a NPN or PNP?


    Have a look at the transistor's data sheet. It will tell you the type and
    the pin layout.


    > 6. The transistor tester has letters around the circle, e E B c E e c
    > b. What's the story there? How do you know which to use?


    B: base, C: collector, E: emmiter. Check the transistor's data sheet and
    connect each pin to the corresponding point on the multimeter.


    > If anyone has a good reference that will answer similar questions, that
    > would be much appreciated. I had a look at some sites offering
    > multimeter basics, but weren't quite basic enough :)


    You probably already know this, but just in case. To measure voltage you set
    the multimeter to a suitable V range and V connectors, and connect the probe
    *in parallel* to the circuit under test. To measure current you select a
    suitable A range and A connectors, and connect the probe *in series" with
    the circuit (i.e., you break the circuit and then insert the probes).

    Hope this helps.

    Regards,
    Costas
    _________________________________________________
    Costas Vlachos Email:
    SPAM-TRAPPED: Please remove "-X-" before replying
    Costas Vlachos, Dec 30, 2003
    #3
  4. "Costas Vlachos" <> wrote in message
    news:bsqj3e$7a7$...
    > "Simon Bartlett" <> wrote in message
    > news:...
    > >
    > > 1. The fused connector is rated to 500v max, 200mA max. Does that mean
    > > 500v at 200mA? If I want to check a circuit running 12v 1A, can I
    > > safely use the fused connector or do I have to use the un-fused
    > > connector?

    >
    > You will have to use the unfused connector. This is because your circuit
    > is drawing 1A and the fused connector is rated at 200mA max. This rating
    > is independent of the circuit voltage (as long as it is below 500V).


    Hmmm, my reply above is a bit misleading...

    Just to clarify, the above is true only if you want to measure the circuit's
    current. For voltage measurement you should use the fused connector (that's
    probably the only connector you can use for voltage measurements anyway).

    So it all depends on whether you are measuring V or I. For V you use the
    fused connector, no matter how much current the circuit draws. For I you use
    the fused one for small currents (up to 200mA) or the un-fused one for high
    currents (up to 10A).

    Apologies for any confusion caused!

    Costas
    Costas Vlachos, Dec 30, 2003
    #4
  5. Thanks Peter and Costas.

    That made a lot of sense. I was trying to read volts with the circuit
    broken, instead of parallel. I now see that one connector is volts up
    to 500v, or Amps up to 200mA, depending on what I'm measuring at the
    time. The other connector is only for Amps (and I was trying to use it
    for volts).

    Again, thanks for all the help.

    Simon

    In article <>,
    says...
    > Hi group.
    >
    > I've always used a multimeter on a trial and error basis, till I get a
    > reading that looks like what I should get. I think it's time now that I
    > try and understand what's going on though. As such, I've composed a
    > list of simple questions, the answers to which would be a great help to
    > me.
    >
    > 1. The fused connector is rated to 500v max, 200mA max. Does that mean
    > 500v at 200mA? If I want to check a circuit running 12v 1A, can I
    > safely use the fused connector or do I have to use the un-fused
    > connector?
    >
    > 2. I was trying to measure a current on a circuit of 12v 1A. To be
    > safe, I used the unfused (10A) connector. I couldn't get a reading of
    > volts at all (perhaps I should have tried amps). Should the 10A
    > connector give identical readings to the fused connector where the
    > current is within the fused connector's range?
    >
    > 3. The Volts DC selector scale has points at 200m, 2000m, 20, 200, 500.
    > Does the m refer to milli as in 200 millivolts, 2000milivolts? Of not,
    > what?
    >
    > 4. The Amps DC selector scale has points at 200(funny u symbol), 20m,
    > 200m, 10. What is the funny u symbol? And again, does the m stand for
    > milli?
    >
    > 5. The transistor tester has NPN and PNP markings. By looking at a
    > transistor, how do I know if it's a NPN or PNP?
    >
    > 6. The transistor tester has letters around the circle, e E B c E e c
    > b. What's the story there? How do you know which to use?
    >
    > If anyone has a good reference that will answer similar questions, that
    > would be much appreciated. I had a look at some sites offering
    > multimeter basics, but weren't quite basic enough :)
    >
    Simon Bartlett, Dec 30, 2003
    #5
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Harry Muscle

    Very very simple question about bridge rectifiers

    Harry Muscle, Dec 17, 2003, in forum: Electronic Basics
    Replies:
    4
    Views:
    491
    P.R.Brady
    Dec 19, 2003
  2. greenwanderer108

    Digital Multimeter : General / Basic questions (DC amps/volts)

    greenwanderer108, Oct 2, 2005, in forum: Electronic Basics
    Replies:
    3
    Views:
    1,883
    w_tom
    Oct 2, 2005
  3. A very basic, BASIC question

    , Jun 15, 2007, in forum: Electronic Basics
    Replies:
    3
    Views:
    461
    Jamie
    Jun 16, 2007
  4. falcon60

    Very, very basic question

    falcon60, Apr 25, 2010, in forum: Microcontrollers and Programming
    Replies:
    4
    Views:
    916
    falcon60
    Apr 26, 2010
  5. Don McKenzie
    Replies:
    0
    Views:
    526
    Don McKenzie
    Jun 29, 2010
Loading...

Share This Page