ALMEMO® measuring system for calibrating climatic chambers

Guideline DAkkS-DKD-R 5-7 lays down minimum requirements for the calibration procedure and for the determination of measurement uncertainties when calibrating climatic chambers. This guideline describes inter alia the objectives, procedures, and methods of calibration, and the uncertainty components involved. The full text of this guideline is available as a PDF document on the home page of the Physikalisch-Technische Bundesanstalt (www.ptb.de --> Metrologische-Dienstleistungen --> DKD --> Publikationen) and can be downloaded free-of-charge.

Calibration of relative atmospheric humidity at nine points in the climatic chamber using precision measuring instrument ALMEMO® 710

The ALMEMO^® measuring system, comprising precision measuring instrument ALMEMO^® 710, one humidity sensor, and eight temperature sensors, can be used to acquire all relevant measurable variables prevalent in the climatic chamber. The relative atmospheric humidity at the nine points in the climatic chamber is calculated in the ALMEMO^® 710 itself. Climatic chambers can thus be calibrated in full and on site quickly and easily.

Humidity is calculated in the ALMEMO^® 710 on the basis of formulae as per Dr. Sonntag and the enhancement factor as per W. Bögel (correction factor Fw(t,p)) for real mixed gas systems). This substantially widens the measuring range and improves the accuracy of humidity variable calculations.

All values, both measured and calculated, are shown in a clear and easy-to-understand way on the ALMEMO^® 710‘s large touch display. The ALMEMO^® 710 also operates as a data logger. Measuring series can be saved either to the internal memory (capacity for over 400,000 measured values) or via the ALMEMO^® memory connector to an SD card (capacity for several millions of measured values).

Assistant for the calibration of climate chambers

WinControl can be used to display and document values e.g. as a line graphic - either online those measured values actually being acquired during a measuring operation or offline after a measuring operation those measured values previously saved. It also provides various evaluation and statistical functions:

• Direct involvement of the climate chambers in the online measurement operation
• Online visualization of the clibration process for all measuring points
• Calculation of local relative humidity measured on the temperature monitoring points
• Determining measurement uncertainties
• Logging of deviations from the display value
• Automatic, convenient analysis with protocol creation in PDF format