Results 1 to 6 of 6

Thread: Can digital multi meter function as a tachometer?

  1. #1
    Registered User
    Member ID
    CZCC-30732
    Join Date
    Aug 2014
    Location
    Central Ohio
    Posts
    35

    Default Can digital multi meter function as a tachometer?

    Well, the dwell/tach that I bought in 1969 finally died! They just don't build them like they used to, or wait a minute - they did build them pretty good back then.

    I used the dwell very seldom since adding the Pertronix to my '72 240Z. But I did use the tach function often when tuning carbs or setting timing. Very handy when you don't have a helper!

    My question is - I have a digital multi meter (DMM) that has a lot of functions but does not have a tachometer function. I always hooked up the '69 meter up to the distributor side of the coil and the other lead to a ground. Is there a function on these meters that would give me the rpm reading (I understand that there may be a decimal point that might be off)?

    Has anyone tried this, is there a simple setting + math, or am I out of luck and will have to buy a new meter just to check RPMs occasionally?

    Thank you for any help and advice.
    John

  2. #2
    Low Budget/High Value
    Member ID
    CZCC-20342
    Join Date
    Oct 2009
    Location
    Washington County, OR
    Posts
    3,629

    Default

    If you have a DC hertz (DC Hz) setting you can get some numbers and do math. Your coil will fire 3 times per crankshaft revolution, and the meter should pick it up from the coil negative to ground. I've used my Fluke 115 that way to determine that my tach was off by 200 RPM.

    The tachometer function on a higher grade meter probably uses the same measurement but does the math for you.
    1976 280Z, with some minor modifications

  3. #3
    Registered User
    Member ID
    CZCC-30732
    Join Date
    Aug 2014
    Location
    Central Ohio
    Posts
    35

    Default

    Hi Zed and thank you for the info.
    I have an older Fluke 77 but it doesn't have very many settings. I also have a Cen-Tech P37772 that I picked up last spring. Hz is one of the settings, but it does not say DC or AC. I am going to make an assumption that it is DC. Hope so anyway.

    I thought I had it hooked up once at some DC volt setting and got a reading similar to the tach, but I could be mistaken.

  4. #4
    Registered User
    Member ID
    CZCC-3609
    Join Date
    Feb 2003
    Location
    Clearwater,Florida USA
    Age
    74
    Posts
    4,424

    Default

    If you used the old one for 45 years - time to treat yourself to a new one. AMAZON or SEARS..
    Sears.com

    FWIW,
    Carl B.

  5. #5
    Nova Scotia,Canada,Earth Blue's Avatar
    Member ID
    CZCC-7641
    Join Date
    Jan 2005
    Location
    NS
    Posts
    4,085

    Default

    I had one of the actron multimeters that read rpm from coil but it failed like most modern junk:
    Amazon.com: Actron CP7677 Automotive TroubleShooter - Digital Multimeter and Engine Analyzer: Automotive

    I now use a timing light with tach feature that reads off a plug:
    Timing Light with Digital Tachometer


    You could this type of device with a mark on the damper:
    Digital Laser Tachometer | Princess Auto
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


  6. #6
    1978 280Z (stock) TomoHawk's Avatar
    Member ID
    CZCC-2169
    Join Date
    May 2002
    Location
    NorthCoast, Ohio
    Age
    58
    Posts
    6,497

    Default

    My tablet PC has an application that can convert the sound to RPM. It's pretty close.

    OTOH, we used to build those little converter boards in school to convert stuff (like RPM, capacitance, etc.) to resistance, so you could use the volt meter.

    What would be REALLY nice would be to hook up an exhaust sniffer or something to tune the fuel mixture.
    Last edited by TomoHawk; 10-22-2014 at 09:11 AM.
    Drive Responsibly.
    enjoy classic Rock music.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Multi Z owner
    By Edz280zx in forum Introductions and Z Stories
    Replies: 5
    Last Post: 12-08-2008, 09:55 AM
  2. A/F ratio meter on multi-carb setup...?
    By lww in forum Engine and Drivetrain (S30)
    Replies: 1
    Last Post: 11-13-2004, 07:25 AM
  3. Multi Switch
    By Jimmy240Z in forum Electrical (S30)
    Replies: 0
    Last Post: 09-25-2004, 08:13 AM
  4. LM-1 Digital AFR Meter, anyone try one out?
    By landmizzle in forum Carburetors (S30)
    Replies: 0
    Last Post: 02-17-2004, 08:25 PM
  5. Multi-ground...
    By Zvoiture in forum Electrical (S30)
    Replies: 2
    Last Post: 01-05-2004, 02:55 PM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •