2.2
Application
Hart Scientific metal sheath SPRTs are classified as primary standards. A pri-
mary standard is defined in terms of transfer of the ITS-90 from a standards
laboratory to a customer’s laboratory. Primary standards are calibrated in a
standards lab using known intrinsic values.
2.3
Calibration
In order for any instrument to be used as a standard it must be calibrated. The
SPRT may be purchased calibrated or non-calibrated. Hart has the capability to
perform fixed-point or comparison calibrations traceable to NIST. They can be
economically calibrated using the comparison method or any one of several
fixed-point calibrations matching ITS-90 subranges.
2.3.1
Calibration Intervals
Accuracy required for the application and the condition of use dictate the cali-
bration intervals. Calibration checks at the triple point of water should be ac-
complished periodically and the results recorded. Once a written history of the
SPRT is available, calibration intervals can be adjusted. The SPRT does not
need to be recalibrated as long as the change in resistance does not exceed the
owner’s specifications.
Depending on the user’s Quality Assurance requirements, the SPRT drift
should be checked periodically at the Triple Point of Water (TPW). Section 8,
Troubleshooting, provides information on drift with respect to mechanical
shock and oxidation. If the R
tp
cannot be restored after annealing to within cali-
bration tolerances, a full recalibration should be scheduled.
2.4
Recalibration
The recalibration of the SPRTs should be scheduled according to the user’s
company Quality Assurance requirements. Normally, an SPRT is recalibrated
annually. Unless the SPRT is used only over a limited range, calibration over
the full range of the SPRT (–200°C to 480°C for the 5680 and 5682, and
–200°C to 661°C for the 5699) is recommended. For information on
recalibrating your SPRT, contact a Hart Scientific Authorized Service Center
(see Section 1.3) for calibration options, an RMA number, and current pricing.
2.5
Return Procedure
Call an Authorized Service Center for an RMA number before shipping.
Extreme care must be taken in shipping a SPRT. Place the thermometer in its
factory provided protective storage case. Be sure the case is latched securely.
Place the protective case in the original manufacturer’s wooden shipping crate
or wooden crate with similar dimensions (44 1/2 in. x 11 3/4 in. x 11 3/4 in.).
5680/5682/5689 SPRT
User’s Guide
6
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