We (people actually in the calibration industry) often hear things being called calibrators that obviously aren’t. A great example is the Emerson HART(tm) communicator. No offense intended, but these types of devices aren’t calibrators, they are electronic “screwdrivers” that enable a technician or engineer to adjust the calibration of a device.

Here are my defining points for a calibrator.

1. Can make a precision measurement or generate a precision signal (i.e., analog, not digital). Or BOTH.
2. Has a calibration that is traceable to national standards.
3. Has a known accuracy or degree of calibration uncertainty.

There is a lot that could be added to this list, of course; things such as conformance to international standards, EX ratings…

Another little list of mine is this list of characteristics that make up a good calibrator.

• Accuracy
• Flexibility or versatility
• Ease of use
• Reliability
• Ergonomics (small, lightweight, easy to read display, etc.)
• Value

To me, a great example of all of the above is the Martel BETA MC-1200 Multi-function Calibrator. It’s got a long list of features, top knotch performance and is a great deal for the money. Total cost of ownership is good because all they ever require is annual recalibration which anyone with a computer and adequate standards can do.

I’m not referring to an old time game show or parlor game as they used to be known. My question is, “Can you trust your vendor’s calibration certificate?”

There are a few indicators you can use.

1. What kind of reputation does the company have in the industry? You know, how long have they been around and do other customers respect their products and service? There are a number of industry surveys and reports that can help with this if you don’t feel comfortable making your own assessment.
2. Is the certificate traceable to NIST or other national standards body? This may seem obvious, but read the statement see if it makes sense to you. Are there unsupported assertions about things like TUR (Total Uncertainty Ratio) or Guide 25 approval?
3. Are the standards used properly identified and are they appropriate for the task at hand? For example, if a specification is % of reading, but the standard’s specification is % of scale, there’s a significant mismatch. You may also need to check to see if the standard has been properly maintained with acceptable calibration intevals.
4. Does the certificate include data that is clearly presented and meaningful? Are there sufficient data points to assess performance?
5. If possible, check the calibration at intervals different from the cardinal points on the certificate. Even a bump check can provide revealing information.

Finally, is the calibration accredited under an international standard (ISO 17025) or do you need such an accredited calibration. Even if it’s offered as an option, the vendor must have a pretty good idea that the normal calibration is valid.

Sometimes we don’t do a good enough job letting people know what they are getting for their money.

As a rule, I would say that we give people a working product with everything that’s needed to put it to work right away. We even include BATTERIES.

T-140 Kit Ship Sheet

To see what we really ship with a product, I look at what we call the Ship Sheet. This is the guide for the shipping department to make sure that nothing is forgotten or left out of the box that’s supposed to be there.

You can see an example to the right. This is the ship sheet for a low range T-140 pressure calibrator kit. Here’s what’s in the box:

1. The calibrator (T-140)
2. The instruction manual
3. NIST calibration certificate
4. Hard plastic carrying case with foam insert
5. MECP100 pneumatic hand pump
6. Labels for the pump
7. Various fittings
8. Tubing cut to a 3′/1m length
9. Teflon tape
10. Shipping bag for the calibrator
11. Product registration postcard
12. Thank you card
13. Label for the carrying case

So, everything you normally need is there.

Unlike some manufacturers, Martel provides a useful calibration certificate with each calibrator at no additional charge. The only exception is the old MS-420, which does not have a display and therefore there is no actual data to document.

By useful calibration certificate, I mean the following:

1. The certificate identifies the specific instrument involved by model number and serial number.
2. The certificate identifies the specific standards used for the calibration by model number and serial number, and provides evidence that the standard’s own calibration was within a valid date range.
3. The certificate includes data for each test point. This includes the value applied or measured by the standard and the comparable data for the calibrator being tested. Further the deviation from the expected data is recorded and a pass/fail test is applied.
4. The total uncertainty ratio (TUR) for each test point is provided if it is less than 4.
5. The technician who performed the test is identified.
6. Martel’s internal test procedure is identified.
7. Our “Statement of Calibration” is included on the certificate.

In addition to all of this, we save ALL of this data and can reprint the certificate upon demand when the customer cannot locate their copy (the one the originally came with the instrument).

Further, our calibrations conform to the ANSI Z540.1 standard. This is also included on the calibration statement at no charge.

We, hope and plan to be able to offer accredited calibrations under the ISO 17025 standard at some future point. In the meantime, we use a 3rd party to provide an accredited calibration certificate at extra cost for any customer who needs that.