Voltage Reference off spec or normal?

Discussion in 'General Electronics Chat' started by illusive, Jan 27, 2016.

  1. illusive

    Thread Starter Member

    Jul 9, 2015
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    0
    Hi,
    I needed a 2.5V reference voltage and i bought a LM4040BIZ-2.5.It is 2.5V ±0.2% shunt regulator but when i connect it with a series resistor i'm reading about 2.47 volts no mater what load current i set (up to 15mA). Is this within spec or am i doing something wrong?
     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    Without a schematic I can only guess that your meter is off.
     
  3. Papabravo

    Expert

    Feb 24, 2006
    10,152
    1,793
    Let's see.

    \frac{.030}{2.5}\;=\;0.012 \;= \;1.2%

    Seems like it is out tolerance. When was your meter last calibrated? You do calibrate your instruments at least once a year per ISO-9001 -- right? Did you get the little sticker from the independent lab that did the calibration?
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,037
    3,243
    Find another meter to check the voltage.
     
  5. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
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    What kind of meter are you using?

    @crutschow
    That was your 10,001th post, very cool!!
     
  6. illusive

    Thread Starter Member

    Jul 9, 2015
    46
    0
    Yep, i measured it with another multimeter and sure enough - 2.503V
     
  7. Papabravo

    Expert

    Feb 24, 2006
    10,152
    1,793
    So which one do you believe? Are you going to get the first meter professionally calibrated? Is that first meter just a throwaway cheapie that probably can't be calibrated anyway?

    2.5 \times 0.002 = 2.505

    2.503 \le 2.505

    Looks like a winner, and you have a new voltage reference to check meters with.
     
  8. illusive

    Thread Starter Member

    Jul 9, 2015
    46
    0
    It was a six years old 20 dollar one, so i bet it is off.
     
  9. Papabravo

    Expert

    Feb 24, 2006
    10,152
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    Not exactly instrument grade, then. I would label it with ±2.6% sticker just to remind yourself.
     
  10. Lestraveled

    Well-Known Member

    May 19, 2014
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    Here is EEVblog rant on cheap multimeters.

     
  11. Papabravo

    Expert

    Feb 24, 2006
    10,152
    1,793
    Amen. Words to live by. BTW I have a Fluke 77 and a Fluke 117. The Fluke 117 was a perk to my wife, who was a purchasing agent, from a sales rep. I was happy to put it to use.
     
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