In-Situ Thermal Mass Flow Meter Calibration Validation скачать в хорошем качестве

In-Situ Thermal Mass Flow Meter Calibration Validation

One of the great benefits of thermal mass flow meter technology is in-situ calibration validation. Learn how the DrySense sensor stability found in Sierra thermal mass flow meters is the only way in-situ calibration validation is actually valid. Sensor drift can create false positives and reduce the reliability of validation. Only with sensor stability that Sierra’s thermal mass flow meters possess can users truly validate a thermal mass flow sensor’s factory-calibrated accuracy in the field. More info: http://www.sierrainstruments.com/libr... [Video Transcript] Industrial thermal mass flow meters comprise a family of instruments for precision measurement of total mass flow rate of gases in pipes and ducts. So when evaluating thermal mass flow meters for in-situ calibration validation capability, be aware that sensor drift will create false-positives, reducing the reliability of the validation. Wet thermal sensor design, because of the organic potting cement used, would shift and crack over time, causing unwanted sensor drift, resulting in gradual degradation of flow measurement accuracy. Today, wet thermal sensors are used by all industrial thermal sensor manufacturers on the market. With one exception, Sierra. Sierra never stopped improving the technology, knowing that wet sensor drift problems must be solved. After all, by its very principle of operation, a thermal sensor is heated and cooled over time, expanding and contracting the cement inside the sensor. Making it crack, settle, and shift from its original state. Dr. Olin believed there had to be a better way. He needed to get rid of all cements to make a stable thermal sensor. In 1999, Dr. Olin patented a breakthrough thermal sensor design. Like other thermal mass flow sensors, it was made of platinum resistance temperature detector wire, wound around a ceramic mandrel, but this was where the similarities ended. Through a proprietary highly controlled manufacturing process, a metal sheath is tightly formed on the mandrel and wire assembly to be in such intimate contact that no air gaps exist and no organic filler cements are needed. This new sensor was literally all metal. In contrast to wet sensor design, this innovative cement-free sensor is known as a dry sensor, patented by Sierra as DrySense. Because the all-metal DrySense sensor is so rugged, reliable and stable, Sierra is the only company offering a lifetime warranty. Quality systems like ISO 9000 may require annual or semi-annual calibration and validation of all measurement instruments in a facility. One nice feature of thermal mass flow meters is the calibration can be easily validated in the field at a very low cost. In-situ, or field calibration validation of thermal meters is a highly marketed feature because it saves money on calibration and downtime. Sierra's motto is: Don't re-calibrate, validate. But be careful, there's a lot more going on behind this statement than you may first think. There's a lot of smoke and mirrors by thermal manufacturers about in-situ calibration. All thermal meter manufacturers have generally the same method of in-situ calibration validation to confirm the original factory calibration, while checking for drift and assuring accuracy. The basic process makes use of the electric characteristics of the sensor, either by checking that the electrical resistance of the velocity sensor's platinum resistance temperature detector wire has not changed over time. Or by assuring that the power sent to the velocity sensor at zero flow is the same as when it was first calibrated at the factory. The problem with both methods is that they only measure the characteristics of the internal sensor windings and don't address sensor drift. The big question is, how can you validate a sensor that will drift out of spec due to the nature of its mechanical design? The resistance of the platinum wire shouldn't change, and the current running through the sensor might be the same, both of which would validate okay. This is a false-positive, as the drift inherent in a wet sensor design would remain unseen. Sierra's DrySense all-metal, no-drift sensor has a big advantage during in-situ calibration validation. You have the mechanical design confidence that there will be no drift, and that in-situ calibration validation is indeed actually valid. Sierra offers a free in-situ calibration validation software package, ValidCal diagnostics. Unlike other validation routines, ValidCal provides a complete check of all meter's components, including, the velocity and temperature sensors, sensor drive circuitry, accuracy, the pressure transducer, and all digital and analog outputs at alarm relays. When complete, a detailed calibration certificate and diagnostics report is created. All of this can be accomplished without even removing the meter from the processed piping.