Voltage Reference off spec or normal?

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

Jul 9, 2015
46
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
1,233
Without a schematic I can only guess that your meter is off.

3. Papabravo Expert

Feb 24, 2006
11,683
2,455
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
19,805
5,543
Find another meter to check the voltage.

5. Lestraveled Well-Known Member

May 19, 2014
1,957
1,233
What kind of meter are you using?

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

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

7. Papabravo Expert

Feb 24, 2006
11,683
2,455
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.

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
11,683
2,455
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
1,957
1,233
Here is EEVblog rant on cheap multimeters.

11. Papabravo Expert

Feb 24, 2006
11,683
2,455
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.