Edgetech RH CAL, Руководство оператора

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6.0 N.I.S.T. TRACEABILITY
– WHAT DOES IT MEAN?
The RH-CAL, or Relative Humidity Calibrator, is certified by Edgetech Instruments Inc.
to be traceable to N.I.S.T., the National Institute of Standards and Technology (formerly
known as the National Bureau of Standards, or NBS), in Gaithersburg, Maryland, U.S.A.
You have received a Certificate of Calibration with this instrument. What does N.I.S.T.
Traceability mean in terms of the RH-CAL?
The calibration chamber in the RH-CAL can be set by the user to any desired relative
humidity (RH). The instrument measures and controls the chamber RH by measuring
both the air temperature (AT) and the dew point temperature (DP) in the chamber.
Since there is a mathematical relationship between dew point temperature, air
temperature, and relative humidity, a built-in microprocessor can therefore compute the
chamber RH.
Dew Point is a fundamental measurement of humidity. It is not affected by temperature.
In addition, the chilled mirror dew point sensor in your RH-CAL provides a primary
rather then a secondary measurement of dew point temperature.
Both the AT and the DP are measured with Platinum Resistance Thermometers (PRTs).
These devices are coils of nearly pure platinum, where the rate of change of resistance
with temperature is precisely known. Resistance is accurately measured and is
automatically converted to temperature information in the RH-CAL.
TRACEABILITY:

1. The precise platinum thermometers are N.I.S.T. traceable by the traceable
resistance standards maintained by the PRT manufacturers.

2. A multi-point dew point calibration is performed on every RH-CAL chilled
mirror dew point sensor, using Edgetech Instruments Inc.
’s traceable secondary
dew point standard. This instrument, a precise chilled mirror hygrometer, is
periodically sent directly to N.I.S.T. for certification against their dew point
transfer standard, a Two-Pressure Generator.