cdnelectrician

I was just wondering how many of you send your DMM's in for calibration. I have a Fluke 26-3 I bought in 1998 that I was thinking of sending in for calibration. Although for the measurements I often do, I don't think it would benefit me much.
When I have some spare cash kicking around I'm going to buy an 87-5 but till then the 26-3 is my bread and butter.

Thoughts?

Speedskater

Unless you have a legal or contractual need, I don't see much of a point for DMM calibration. The following is a little test I did last February of the meters that I had handy. Most were near or better than 1 % even the $4 ones.

Using my Keithley 2000 as reference I checked the following units.

Keithley 2000 6½ digit, multi-meter. From about 2001 $1200.
Keithley 177 4½ digit, multi-meter. About 30 years old, currently $375.
Fluke 8020A 3½ digit, multi-meter. About 30 years old.
Radio Shack True RMS 3½ digit, multi-meter. Maybe 8 years old.
Kill-a-Watt P4400 3½ digit, plug-in-meter. About 1 year old.
M8303½ digit, multi-meter. Similar to the yellow Harbor Freight units.
From an outlet store $4. About 5 years old.
Harbor Freight Cen-tech DMM’s
Cen-tech 92020 3½ digit, multi-meter. $4. About 1 year old. Very noisy.
Cen-tech 95683 3½ digit, multi-meter. Under $20. 4 months old. w/current clamp.

None of the meters have been calibrated.

Keithley 2000
Keithley 177
Fluke 8020A
R/S 22-1758
Kill-a-Watt
M830
92020
95683


AC Accuracy of the Keithley 2000 when reading a 120V AC 60 Hz signal
is calculated to be ±0.297V. Yep, not nearly as good as one might expect!
The accuracy takes a big hit when using the 750V range.
If we measure 99V on the 100V range then it” ±0.09V.

AC Accuracy of the Keithley 177 when reading a 120V AC 60 Hz signal
is calculated to be ±1.03V.

The line voltage is a little high, because it was 55°F all night in Cleveland (it’s now 28°F). Not much power using activity in the neighborhood mid-day Friday.

Lone Crapshooter

I think what would determine the need for calibration is what voltage level you are working with.
If you are doing electrical service work you really dont care if the motor is being fed by 479 or 480 volts. If you are working in a lab doing board level work yes it should be calibrated at least on a yearly interval.
Anouther thing is the age of the meter and the cost of replacement . Transcat and Davis are proud of theri calibration service. Your meter is 11 years old it might not be worth the cost of calibration.
If you are doing process instrumentation and control work loop calibration equipment should be calibrated every year but it is more expensive than your standard DMM
LC

Zog

Certified testing companies are required to have all of thier test equipment calibrated every year. Any one doing any real testing should do the same, most testing specs require the test equipment to be calibrated, the serial number and calibration date to be on the test form and a calibration certificate to be on file to be provided if necessary.

Every company I have ever worked for has had all of thier meters calibrated annually, even if not required. I have seen about a 10-20% calibration failures over the years, and thats all quality equipment.

I am shocked this is even an issue, do some poeple really not calibrate thier meters???

480sparky

Or their torque wrenches?

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paul d.

i think most of us " test " our meters by actually using them. if i'm looking for 277v, does it matter if i get 276 or 278 ?? but there is a big difference between testing and measuring.

cdnelectrician

I suppose you are all right, the most in depth stuff I get into is fire alarm, process controls and drives. It's time for a new meter anyways!

Just wanted to get an opinion on the matter...