Voltage Reference off spec or normal?

illusive

Joined Jul 9, 2015
46
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?

Lestraveled

Joined May 19, 2014
1,946
Without a schematic I can only guess that your meter is off.

Papabravo

Joined Feb 24, 2006
12,767
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?

crutschow

Joined Mar 14, 2008
24,047
Find another meter to check the voltage.

Lestraveled

Joined May 19, 2014
1,946
What kind of meter are you using?

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

illusive

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

Papabravo

Joined Feb 24, 2006
12,767
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.

illusive

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

Papabravo

Joined Feb 24, 2006
12,767
It was a six years old 20 dollar one, so i bet it is off.
Not exactly instrument grade, then. I would label it with ±2.6% sticker just to remind yourself.

Lestraveled

Joined May 19, 2014
1,946
Here is EEVblog rant on cheap multimeters.

Papabravo

Joined Feb 24, 2006
12,767
Here is EEVblog rant on cheap multimeters.

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.