TP 28 1300 E
Guideline DAkkS-DKD-R 5-
4 • Appendix B
Technical changes reserved
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Guideline DAkkS-DKD-R 5-
4 • Appendix B
Details of the DKD technical committee "Temperature and Humidity" for the operation of tempera-
ture block calibrators.
Having a calibrator certificate from a DAkkS calibration laboratory confirms that the temperature
block calibrator meets the high demands of the calibrating ability of such a device, which are outlined
in the guideline DAkkS-DKD-R 5-4. Nevertheless, the following points should be noted regarding the
use of the calibrator:
The calibration of the temperature block calibrator predominantly relates to the temperature of the
solid body block. The temperature of the thermometer in the block to be calibrated can differ from
this temperature. If a thermometer of the same model, under the same test conditions as were used
in the calibration is used, it can be assumed that the measurement difference in the calibration of
ideal thermometers are not larger than the measurement inaccuracy which is stated in the calibrator
certificate. If it is the case that nothing else is specified on the calibrator certificate, it must be en-
sured that
•
the measuring element is located in the homogeneous temperature zone.
•
the inner diameter of the bore hole used in the calibrator (possibly the casing) in the tempera-
ture range of –80 °C to 660 °C is a maximum of 0.5 mm bigger than the outer diameter of the
calibrated thermometer, and in the temperature range of 660 °C to 1300 °C is a maximum of
1.0 mm bigger.
•
the immersion depth of the thermometer to be calibrated amounts to at least 15 times the outer
diameter of the thermometer to be calibrated.
•
the thermometer to be calibrated has an outer diameter of d < 6 mm.
Please take particular care if a heat transfer medium was used during the calibration of the tempera-
ture block calibrator. If this is the case the calibration is only effective if the calibrator was used with
a corresponding heat transfer medium.
With the calibration of thermometers with an outer diameter d > 6 mm allow for an additional error of
measurement due to heat conduction. In the case that such measurements are required, the addi-
tional heat conduction can be determined by the thermometer model and ascertained from your ac-
credited calibration laboratory. A good test of the possible temperature variations caused by heat
conduction consists of testing whether the display of the calibrated thermometer changes when it is
lifted 20mm. Contributions to measurement inaccuracy that are conditional on the thermometer to be
calibrated (e.g. inhomogeneities from thermal elements), are likewise not covered in the measure-
ment inaccuracy of the calibrator.
In the case that the calibrator is used in load conditions that do not comply with the load condition
from the calibration, the influence of the load condition can be determined through replacement or
addition of other thermometers on site.
The details on the calibration certificate are important for the calibration, not the manufacturers' in-
structions. Before the calibration, please make sure you agree upon the operation and calibration
conditions with your DAkkS calibration laboratory.
If there is nothing else specified on the calibrator certificate, (independent from the manufacturers'
instructions) it must be ensured that
•
the calibrator is used in a vertical position.
•
no additional thermal isolation is in use.
•
the environmental temperature is (23 ±5) °C.
In order to check the calibration of the temperature block calibrator it is recommended to take regu-
lar measurements with a calibrated thermometer. If control measurements with a calibrated ther-
mometer are not taken annually, recalibration of the temperature block calibrator is strongly rec-
ommended.
© Deutsche Akkreditierungsstelle GmbH (German Accreditation Body)
•
E-Mail: contact
@
dakks.de
•
Internet: www.dakks.de
