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converting probles to clamp-on

Discussion in 'Electronic Basics' started by *selah*, Jul 18, 2005.

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  1. *selah*

    *selah* Guest

    Is there some adapter device that can convert from plug-in probes to
    clamp-on? (like for an ammeter).

  2. mike

    mike Guest

    Yes, you're welcome.
    A more specific question might elicit a more specific answer.

    Return address is VALID but some sites block emails
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  3. Tristar500

    Tristar500 Guest

    check out item number CAT# MTC-21 at the website.

    set of 2 for $3.00.

    Going to order a couple myself.

  4. Chris

    Chris Guest

    Hi, Selah. Unless you're waiting for someone to write a novel to cover
    every possible answer, you might want to be a little more specific:

    * Do you already have an existing meter you want to use? If so, which

    * Are you interested in measuring DC current, AC current, or both?

    * If AC, what are the frequencies of interest? Is it a sine wave or
    other waveform?

    * What kind of accuracy do you need in this measurement?

    If you're just interested in a clamp-on ammeter for measuring AC with
    limited accuracy, you can get cheapie DMMs with a clamp built in for
    measuring AC curent at line frequencies for less than $20 USD. They're
    available at Harbor Freight and other sources. This might be less
    expensive than purchasing an adapter.

    If this doesn't do the job, looking forward to getting more

    Good luck
  5. JeffM

    JeffM Guest

  6. *selah*

    *selah* Guest

    It's a micronta digital.
    dc - for now.
    ..05 mA - the meter has a dc mA setting and setting for 2 mA. I want to
    use it to see if the current drain in our car is within range.
  7. *selah*

    *selah* Guest

    Oops - sorry. I just realized - the manual calls for .05A sensitivity -
    not mA - so I can't use this meter. Got it confused because the test can
    also be done with a shunt and a meter that has .05 mV sensitivity.

    Thanks for the responses anyway.
  8. mike

    mike Guest

    This is going from bad to worse.
    You've got people willing to help, but you're not very forthcoming.
    Your numbers are inconsistent with the words. Very few things in a car
    can be measured with a 2mA meter. Assuming we have the same notion of
    what constitutes a "car".

    What the heck are you trying to measure...EXACTLY.
    And just for fun, what are you gonna do if you don't like the number?

    Return address is VALID but some sites block emails
    with links. Delete this sig when replying.
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  9. ehsjr

    ehsjr Guest

    You more than likely can use the meter.
    ..05 A = 50 mA and it is likely that your meter has a
    range that will accomodate that. On your next post,
    tell us the model number of the Micronta meter, and
    what the current measuring ranges are. Also, as other
    posters have indicated, the information you provide
    is incomplete, making it next to impossible to give
    you a good answer. For example, you say "the manual
    calls for .05A sensitivity". What manual? What is
    the manual telling you to do? Why are you doing it -
    what problem are you trying to solve or what information
    are you trying to gather? etc.

  10. *selah*

    *selah* Guest

    The model # is 22-191

    The current drain is supposed to be less than .05A.

    Also, as other
    Ford shop manual.

    What is
    Battery Drain Test with a Clamp-On DC Ammeter

    Test Procedure

    1. Turn the ignition to OFF and make sure there are no electrical loads.
    After determining that the underhood lamp is shutting off properly,
    disconnect the bulb.

    2. Clamp the meter clip securely around the positive or ground battery
    cable (all cables if two or more leads to the post).

    Do not start vehicle with clip on cable.

    Test Conclusion

    The current reading (current drain) should be less than .05 amps.

    Why are you doing it -
    Our battery went dead recently although we just bought it new. We
    recharged it. The charger showed that it was at very low charge at the
    beginning (the charger ammeter was showing 10A going to the battery),
    after about 6 hours it was fully charged and the charger ammeter showed
    4A going to the battery. I tested the battery with a hydrometer and the
    hydrometer practically didn't float, (it read at the top of the tube in
    the dead battery region.) We took the battery in to a repair shop and
    they tested it with their "snap-on" tester. I assume it was a load test.
    It said the battery was good. These are the results:

    Battery size 660 CCA
    Available Amp 798 CCA
    % Rated Capactiy 120%
    Battery Temp 70 F
    Initial Volts 12.90 V
    Final Volts 12.33 V
    Impedance 4.00 m ohms

    They also tested the alternator (good) and starter (good).
  11. mike

    mike Guest

    This is odd. Your hydrometer says it's dead, but the shop says it's
    good. Sounds like a hydrometer problem.

    (it read at the top of the tube in
    You don't say how old your car is. I have no experience with all the
    new electronical stuff in cars. I'd think it would be safe to (somebody
    correct me if I'm wrong) take a 1 ohm 1/4W resistor in series between
    the battery and the positive wire. If the resistor explodes, you've got
    too much current drain. Shouldn't get warm at all. Measure the voltage
    across the resistor. 50mV = 50mA. Don't turn on any lights or anything
    while you do this cause you will explode the resistor.

    Probes capable of measuring 50mA DC with holes that will fit around the
    size wire you're measuring are hard to find. And they ain't cheap.
    I've got a FW Bell CG100 DC current probe that I was gonna take to a
    swap meet next week and try to get $50 for if you're interested. Only
    reason it's anywhere near that cheap is that someone took it apart. I
    had to reassemble it and make new labels. Appearance is everything with
    resale value.


    Return address is VALID but some sites block emails
    with links. Delete this sig when replying.
    Wanted, PCMCIA SCSI Card for HP m820 CDRW.
    FS 500MHz Tek DSOscilloscope TDS540 Make Offer
    Wanted 12" LCD for Compaq Armada 7770MT.
    Bunch of stuff For Sale and Wanted at the link below.
  12. Chris

    Chris Guest

    Hi, Selah. As is frequently the case, the shop manual for the car is
    assuming you have tens of thousands of dollars in factory-approved,
    factory-supplied equipment. Given that armamentorium, their bean
    counters have determined the least expensive, least labor-intensive
    method of making the measurement.

    I've had your problem before -- an infuriating slow leak of unknown
    origin that drains the battery over a day or two. Here's the simple
    low tech way to approach the problem:

    Before starting this, put a cover over the positive battery terminal
    and clamp to prevent accidentally shorting it out. And use goggles
    while doing this.

    Now, with the key in the OFF position and all accessories turned off,
    place your DMM on DC current. Then use alligator clips to connect the
    leads of the DMM to the negative terminal of the battery and the
    negative battery clamp. Carefully loosen the nut for the negative
    clamp, and then carefully remove the clamp from the terminal. At that
    point, the circuit and leakage current should be from the POS terminal,
    through the car, then through the DMM ammeter to the NEG terminal. You
    can then measure the current (which should be less than 0.05A, or 50mA,
    according to your manual).

    You may have to just use the test probe instead of an alligator clip,
    if you don't have a dual terminal battery. In that case, just hold the
    probe right on the negative terminal as you carefully twist off the
    negative terminal clamp.

    For newer cars, it can be a big pain to reset and reprogram stuff if
    the battery is removed from the car electrical system. However, the
    added series resistance of the DMM on DC current shouldn't cause enough
    voltage drop to make the computers reset, as long as it's less than a
    couple of amps. Avoid even momentarily opening the circuit here, or
    you might have a lot more problems.

    When this happened to me, I did the above and found about 1/4A of
    "leakage" current when everything was supposed to be off. Of course,
    it took over an hour to finally track down that a small normally closed
    switch for a little convenience bulb in one of the convenience
    compartments was jammed in the ON position, even with the convenience
    compartment door closed. How inconvenient.

    You also always have the option of buying a Hall Effect meter clamp,
    which should set you back quite a few bucks. This clamp uses a hall
    effect sensor to sense the magnetic field produced by the current
    flowing through the wire, and outputs a DC and/or AC voltage
    proportional to that current. Several manufacturers make them, they're
    all probably too expensive for what you want.

    I hope this is of help. If you're not familiar with car electrical
    work, you should let someone qualified handle this. And again, don't
    forget to cover the positive terminal of the battery to avoid shorting
    it out if you do handle it yourself. Worst case, you could enjoy a
    sulphuric acid face wash if you're not careful.

    Good luck
  13. P.R.Brady

    P.R.Brady Guest

    Yes, sounds flat.

    I tested the battery with a hydrometer and the
    A assume this was before the charging session.
    Hi Ed,

    so you want to check whether the car is draining the battery when it's idle?

    Have you had any electrical work done prior to your problems like a
    towbar fitting, new radio, new alarm system, new alternator? If so,
    they would be my prime suspects. Look at the car at night for bulbs
    left on (eg interior light, boot light).

    I'd try something very simple rather than risking wrecking the meter.

    With engine stopped, remove the the *** earth connection *** from your
    battery. Note if you get a spark if you re-touch them - an indication
    of a fair load.

    Get a 12 volt bulb, and connect the bulb between battery post and the
    lead you've just removed. Do it by hand - no clips, clamps etc; there
    will be no flashes or bangs if you fumble bulb, lead, post, chassis
    together, provided you stay away from the other post and lead. If a
    headlamp bulb shines like a searchlight you have a real problem - load
    of five or six amps. Can you get hold of one of those 12v to 24v test
    screwdriver things with a bulb in the handle and a trailing lead? Cost
    a few pounds in UK, but test it first by connecting between + and - of
    the battery and don't ever use it for mains testing! Try that for a
    more sensitive test - a mere little tiny glow will be a lot less than
    0.05A = 50mA. If you really want to try the meter to actually measure
    the drain, then do the bulb test first and only use the meter if you get
    a small glow or nothing - try the meter with high current settings
    first. Again, just hold the meter leads against the battery post and
    the lead you've removed.

    If you do get a bulb glowing, then the next step is to find out where
    the current is leaking, and pulling fuses might give a clue. Take your
    bulb off, pull a bank of fuses, (remember where they came from!) try the
    bulb again til you lose the drain. Things like alarm systems, central
    locking, radios with reset codes and clocks do draw a small current,
    probably far less than the 50mA mentioned.

    If having pulled all fuses you still have the drain, remember that some
    circuits might not have a fuse - eg generator, starter via solenoid,
    horn, but your manual will tell you that. Check by disconnecting them.
    A bust diode in the alternator could cause a leak (but might cause
    the ignition warning light to glow?).

    A warning - I was present when a contractor in a telephone exchange
    managed to short an accumulator with a spanner. A nasty big instant
    bang with acid and glass all over the place. Wrap tape round the
    spanner if you work with the positive (non earthed) lead OR disconnect
    the earthed one first.

    Good luck ! Let us all know how you get on.

  14. ehsjr

    ehsjr Guest

    Hi Phil,

    You addressed your note to me - but it was Selah who asked
    the question. That said, your bulb idea is the best, as I see
    it. I don't think Selah fully understands how to use his meter,
    and if he tries, he may end up harming it.

  15. P.R.Brady

    P.R.Brady Guest

    Sorry Ed. Yes, I agree about wrecking his meter. I still think it will
    be worth his while looking for a courtesy light permanently on first
    though! I await the final story.


    Phil Brady
    Information Services
    University of Wales, Bangor
    Adeilad Deiniol
    Deiniol Rd
    Bangor LL57 2UX

    Tel +44 (0)1248 382960
    Fax +44 (0)1248 383826

  16. Rich Grise

    Rich Grise Guest

    Yes, it's called an "alligator clip."

  17. *selah*

    *selah* Guest

    Hello Chris,

    I tried using the probes on the + terminal and the reading was 33 mA.
    Seems maybe the problem was due to a severely corroded wire on the
    starter motor.

    Thanks for the help.
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