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May 12, 2014 160 Views

You already know that before you use a Testo combustion and emissions analyzer, you should calibrate the instrument. That's fairly standard. But what if you get a non-standard reading during calibration?

Our technician was calibrating a unit with 1000 ppm CO, and the unit was reading 800 ppm. Just based on that information, our tech might have calibrated the unit to make the 800 ppm reading come up as 1000 ppm. But then, it'd be reading up to 20% off the true values.

If a calibration is performed on an instrument with even the slightest leak, readings can be significantly different from the readings you would get with a sealed unit. Because of the leak, the instrument may be reading 100% accurately but the value shown doesn’t reflect the value on the bottle.

The solution? First, you leak check the instrument, then you calibrate.

Before calibrating a Testo 330, 335, 340, or 350 series analyzer, you should perform two leak checks:  One on the unit, and on on the probe and/or tubing that's used for calibration.

First, perform a leak check on the instrument to find any internal leaks. Do this by pressing your thumb over the sample inlet, where the probe connects to the instrument.

Next, connect the tubing or the probe to the instrument, and check to see if the sample line is okay.

Once you've determined that your instrument is leak-free and your sample line is good, you can proceed with calibration. And when you do, you can be sure the readings are accurate and an air leak hasn't contaminated your sample.

When our technician followed this procedure, he was able to find a leak in the sample line. Once it was replaced, the analyzer read exactly as expected. Want to learn more?

Posted in: Testo