Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Any Fluke fans out there? (Fluke 87-V DVM questions)

  1. Oct 31, 2016 #1
    Hi all,

    I've bought a barely-used Fluke 87-V from eBay, and it really is a great meter. Far more than what I need as I don't use it professionally, but I hope it'll be the last meter I ever buy. I have a few questions:

    1. If I short the normal test leads in temperature mode, it appears to read ambient temperature, but there is no mention of this feature in the manual. Is this a real feature or an unreliable quirk?

    2. How can I find out the date of manufacture? I have the original box.

    3. In LCD test mode, there are two RPM symbols, but again no mention in the manual. How do I use this feature? It would be handy for setting small engine idle speeds etc.

    4. What can I use the conductance feature for? The range is 0-60 nS. Is it good enough to find insulation faults in transformers?

    5. What use is the smoothing function?

  2. jcsd
  3. Oct 31, 2016 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

  4. Oct 31, 2016 #3
    Sorry, I should have mentioned that I have looked on this site, and in the included manual, but other than a brief account of the conductance and smoothing features I can't find the answers I need. I'd like to know what real users use these things for.

    For example, the manual and site both mention a 'built-in' thermometer, but only talk of plugging in the thermocouple. There's no indication that you can short the leads and get ambient temp.
  5. Oct 31, 2016 #4


    User Avatar
    Science Advisor
    Gold Member

    I am not that familiar with this particular meter but it sounds like what would happen when shorting the inputs to a thermocouple device. A thermocouple device develops a voltage based on the difference in temperature between the shorted end and open end of pair of thermocouple wires. To get an absolute reading, a seperate temp sensor must be used at the measuring end. So, a short circuit to the thermocouple input (zero volts) would cause the meter to read whatever temperature the second temp sensor is.
  6. Oct 31, 2016 #5
    That's interesting, and seems to be what is happening with my meter. Odd that it's not mentioned in the literature, though.
  7. Oct 31, 2016 #6


    User Avatar
    Science Advisor

    You cannot. When the meter was new, a thermocouple was included in the box. It looked somewhat like this:
  8. Oct 31, 2016 #7
    It did come with a thermocouple, but if I short ordinary test leads together in that mode, a temp reading comes up which matches the room thermometer.
  9. Oct 31, 2016 #8


    User Avatar
    Science Advisor
    Gold Member

    Which I explained nicely. To say it cannot is quite simply wrong. A thermocouple gives a voltage based on the temp difference between the shorted and open ends of the thermocouple. It cannot give an absolute temperature reading without a separate temp sensor. So by giving the meter zero input volts this is the same as no temperature difference between the shorted and open ends of the thermocouple wire. The temp displayed will match the temp of the internal sensor in the DVM. I used to work on instruments of this type for a living.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted