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Leak artifacts

Leak artifacts are calibrated in the range 1 x 10-6 to 1 x 10-13 mol/s (2 x 10-2 to 2 x 10-9 std. cm3/s at 0 °C). The calibration can be performed directly against the NIST primary leak standard or can be calibrated on a comparison system with respect to NIST-calibrated reference leaks.

  • Vacuum Leak Primary Standard. This primary standard measures helium flow rates from permeation leak artifacts in the range from 10-13 to 10-6 mol/s. The standard has three major components: a vacuum chamber with a flow orifice and a large turbomolecular pump, the constant pressure vacuum flow meter, and a thermally controlled manifold on which the uncalibrated leak artifact is mounted. The measurement procedure has two steps. First, helium from the uncalibrated leak artifact flows into the vacuum chamber, and the resulting partial pressure of helium is measured by a quadrupole mass spectrometer. Next, the flow from the leak artifact is stopped and replaced by a flow from the vacuum flow meter. The second flow is adjusted to produce a partial pressure helium signal that is close to the signal that was produced by the unknown leak artifact. The known flow rate from the vacuum flow meter and the helium signal ratio determine the flow rate of helium from the leak artifact.
  • Vacuum Leak Comparator. Helium leak artifacts in the range from 10-13 to 10-9 mol/s may be calibrated with respect to NIST-calibrated reference leaks. In this system a mass spectrometer is used to compare the unknown helium leak artifact with a NIST reference leak artifact. This unique calibration service routinely measures leak rate versus temperature over the range of 0-50 °C. This is important because the leak rate of a helium permeation leak artifact may vary by as much as 4% per °C.

Note: Flow rates are quoted at standard conditions for leak measurements of 101 325 Pa and 0 °C. When referenced to the specific temperature, std. cm3/s can be converted to mol/s by multiplying by 4.45 x 10-5.

How to Arrange a Calibration

  1. Contact the staff member in charge of the calibration service for your artifact with any technical or calibration cost questions.
  2. Calibrations are performed in batches. Contact the staff member for scheduling.
  3. Ship your artifact with a copy of the purchase order. Use a sturdy box in which we can return the calibrated instrument.
  4. The purchase order may be sent to contact by e-mail, fax, or mail. Please include the following information:
    • service ID for the calibration
    • model and serial number of your artifact
    • customer contact name, address, phone, and e-mail
    • return shipping method (e.g., shipping account number)

For contact information, shipping address, or cost of calibration, see Low Pressure, Vacuum, and Leak Measurements.

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Technical contact:
R. Gregory Driver
301-975-4832 Telephone

100 Bureau Drive, M/S 8364
Gaithersburg, MD 20899-8364