On May 1, HORIBA STEC obtained an accreditation for its gas mass-flow calibration based on ISO/IEC17025 after the procedural examinations which had been implemented in its Kyoto Fukuchiyama Technology Center. The accreditation body was the National Institute of Standards and Technology (NIST) of the US.

With the accreditation, the company is now able to satisfy the standard flow calibration for itself, and will introduce the calibration system into both Kyoto and Aso plants in early 2018, and aims to make delivery of MFCs based on the cutting-edge fluid calibration. The accreditation has been granted to the gravimetric calibration system developed by HORIBA STEC itself, which consists of an electronic balance and a cylinder installed inside the thermostat chamber in the vacuum condition for calibration. The flow is described as follows:

An inert gas is filled from the gas bottle to the cylinder (34ℓ) through piping, and then gas is supplied from the cylinder to a mass-flow controller (MFC) to be tested. Then the weight of cylinder decreases and a flow output causes at the MFC side, and the electronic balance converts the mass from the weight phenomenon and time of the cylinder to create data for calibration. Briefly speaking, conversion to a mass flow rate is made by the measurement of weight change for a period of unit time.

In this system, there are various ingenious contrivances such as the independent foundations of the sites to install an electronic balance for less influence of the vibrations.

For reference the ISO/IEC17025 accreditation will be examined in the second year after the first granting and reviewed once every other year after then.

Regarding the flow calibration to adjust mass flow controllers, the company has so far been taking advantage of the flow calibration services by other companies which are traceable for the requirements of NIST of USA and NMIJ of Japan. However, with this ISO/IEC17025 accreditation, the company can now bring it internally up to the position of the highest-ranked calibration standard. The accreditation covers a range from 0.012498g/min to 62.49g/min of nitrogen, argon, oxygen, carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), dry air, carbon dioxide (CO2) and nitrogen dioxide (NO2).

Kyoto Fukuchiyama Technology Center, which opened in December 2013, has been engaged since then in the evaporation test of liquid materials in use of flow-rate scale and vaporizer as well as the improvement of flow-rate traceability system for gas MFC and liquid MFC.


Photo: Gravimetric calibration system