Calibrating El-Cheapo Test Equipment

[ScottBP]

We all see this happen all too often: A plant gets dinged on an audit because some auditors find test equipment in a tool room where there is no record of calibration. You know what happens next: Pressured by time, and wanting to satisfy auditors, the manager orders a "sweep" of the tool room and gathers up anything that has a meter needle, scale or digital display and sends them in to be calibrated.

So we end up with a steady stream of el-cheapo test equipment from the employee's tool boxes. You know, things like multimeters bought at Radio Shack, Sears, Wal-Mart, etc. If it were up to me, I'd slap a reject sticker on everything that ain't Fluke or Biddle or Simpson or other professional equipment that has published specifications and calibration procedures, but on the other hand, sure, we don't mind charging a customer more than triple what was paid for a $10-15 meter. But then finding specifications/accuacies is near impossible because one manufacturer often makes equipment for several stores, and nobody knows anything about what they're selling ("You got questions? We have no clue.")

So how best to treat the cheap stuff? Does anyone know where to find the specs for consumer grade test equipment? Or is it in our best interest not to even bother with them and advise our customers to place "calibration not required" or "not for quality measurements" or other similar stickers on the equipment and leave them behind?

 

[Hershal]

There are numerous potential options......

First, if you use an accredited cal lab (or you are one) and have this issue, the military procedures (NA 17-20 series; T.O. 33K series) often have some generic specs for just such an instance, where the brand is not a Fluke or whatever.

Second, in absense of generic procedures, assign a higher value to the tolerance (not MU, it is different) and cal to a broader tolerance.

Third, if in fact the calibration can be ignored because the checks of any importance come after, then a "For Reference Only" sticker will likely work.....but the obvious question becomes.....if this is a measurement that means the product will move to the next step, then doesn't the measurement matter? If yes, then cal the equipment. If no, then why measure? I am paraphrasing Phil Stein only because I don't have the quote right in front of me.

Hope this helps.

Hershal

 

[Jerry Eldred]

I've been through this myself numerous times. I don't disagree with anything Hershal has stated. But I'll present some of my experiences.

This is a very ambiguous topic. I have advised users many times to stick with reliable brand names. Since this is a public forum, I won't name any of the bad brands. I remember one VERY off brand DMM that wouldn't meet spec, we sent it to the mfr, it was returned repaired and cal'd and it still wouldn't meet spec. Bottom line on that one - scrap it. period. In another case, a customer bought three brand new off-brand lookalikes to compete with a Fluke 87. They were all brand new, and none of them worked correctly on AC volts, nor would they align into tolerance.

So answer one is to definitely buy brands that you have reasonable confidence will perform as specified.

Next.... I am an avid researcher for specs. I've been able to find specs on nearly every DMM brand I've come across. Radio Shack is actually not too difficult if you use a little finesse in searching. They actually have spec sheets for many on their website. GIDEP is very useful (if you are able to get access), and I have a number of bookmarks from Taiwan for companies that make some private label meters. All that said, I am not a big fan of off brand meters, as they often do not meet specs.

I firmly believe in test equipment in uncalibrated condition being properly labeled and documented. I would do this before spending a lot of money on unnecessary calibrations to inactive instruments.

Many companies have policies about personal test equipment. If they are bringing the instrument in to work to be used on anything that has any impact on product quality (directly or indirectly), it should be calibrated. Additionally, if it is used where safety could be impacted, it should also be calibrated. If the personally owned test equipment is inadequate for the required measurement, it should not be at work. Unless there are well understood rules to assure the right, calibrated instrument is used where it should be; and inadequate and/or uncalibrated test equipment should be precluded from improper use.

My experience is a good policy for personally owned test equipment is to treat it just like company owned test equipment - adequate accuracy, properly calibrated, documented in the system.

The one thing I would be careful about is placing "calibration not required" on "el-cheapo" test equipment. That could make a bad thing even worse. "Not for use on quality measurements" could be a better avenue, along with assuring everyone implicated understands the ground rules.

To follow up on one of Hershal's points, I have also long believed that if the person needed to use a piece of test equipment to make a measurement, it is an oxymoron to say that accuracy doesn't matter. For example, to measure a 115 VAC outlet: If accuracy doesn't matter, a lightbulb with pigtails is sufficient, and there is no need to a DMM. To measure a thickness where accuracy doesn't matter, a ruler will suffice, and there is no need for micrometers. I'm being a little tongue-in-cheek with the examples, but I hope they made the point. And that is, test equipment is quantitative by nature. Test equipment that is not calibrated does not have a known accuracy, and may lie to you. A defective AC Volts function on a DMM used to check a circuit to see if it is energized can cost lives, and any uncalibrated test instrument has the potential of telling a lie at the wrong time.

The way I deal with customers who bring me an "el-cheapo" instrument is to find the specs, attempt to calibrate it, and use it as a "teachable moment" regarding how well we can depend on our test equipment.

I've rambled on quite long enough. Hope these words are of some help.

 

[The Fast One]

We all see this happen all too often: A plant gets dinged on an audit because some auditors find test equipment in a tool room where there is no record of calibration. You know what happens next: Pressured by time, and wanting to satisfy auditors, the manager orders a "sweep" of the tool room and gathers up anything that has a meter needle, scale or digital display and sends them in to be calibrated.

So we end up with a steady stream of el-cheapo test equipment from the employee's tool boxes. You know, things like multimeters bought at Radio Shack, Sears, Wal-Mart, etc. If it were up to me, I'd slap a reject sticker on everything that ain't Fluke or Biddle or Simpson or other professional equipment that has published specifications and calibration procedures, but on the other hand, sure, we don't mind charging a customer more than triple what was paid for a $10-15 meter. But then finding specifications/accuacies is near impossible because one manufacturer often makes equipment for several stores, and nobody knows anything about what they're selling ("You got questions? We have no clue.")

So how best to treat the cheap stuff? Does anyone know where to find the specs for consumer grade test equipment? Or is it in our best interest not to even bother with them and advise our customers to place "calibration not required" or "not for quality measurements" or other similar stickers on the equipment and leave them behind?

Sack the auditor and the manager...?

 

[Cari Spears]

..."teachable moment"...

I have a couple of friends who are teachers - I love this phrase - and take advantage of teachable moments myself with customers, suppliers, my children, etc.

BTW - "a light bulb with pigtails" - LMAO - good one!

 

[D.Scott]

"a light bulb with pigtails" - LMAO - good one!"

No joke Cari, I use one all the time. You can buy one at the local hardware store.

Dave

 

[Cari Spears]

No kidding - it's a real thing? What are the pigtails?

 

[Jerry Eldred]

Sorry for the jargon in my post. It is a lightbulb in a socket with two unterminated leads connected to the bottom. They are normally referred to as "pigtails."

 

[Cari Spears]

Sorry for the jargon in my post. It is a lightbulb in a socket with two unterminated leads connected to the bottom. They are normally referred to as "pigtails."

Don't be - I learned something new today!

 

[Randy Stewart]

Having gone through this also, here's my 2 cents.

Why was the equipment there in the first place?
If it is being used what is it measuring?
Have there been any rejects that can be traced back to the equipment?
I'm sure you get the picture. If the equipment isn't being used - scrap it or have the person take it home. If it is for other projects and has nothing to do with QA then mark it. If it is being used for a QA measurement and no reject can be traced back to it, then what purpose does the measurment have?
Or is the equipement adequate enough.