Handling Instructions
The calibration standards are to be considered measuring equipment in accordance with international standards and should be recalibrated at regular intervals (see EN ISO 9001, section 7.6 “Control of Inspection and Measuring Equipment“).
The calibration standards must be treated with special care if they are to retain their validity. Scratches, dirt, and corrosion on the optical surfaces can easily introduce substantial errors.
Usually customer choose a recalibration of the solid filters every 12 months for the first two years of use and after that every 24 months, recalibration of the liquid filters not later than every 12 months.
The periodicity of these intervals should be determined by the user and depends on the laboratory environment and the conditions of use. Filters or sets of filters which are sent to us to be recalibrated will be cleaned and calibrated. They will then be returned to you with a new certificate.
Extensive handling instructions are provided with each set of filters.
All filters can also be ordered separately, e.g. as replacement parts, by their catalogue number. The filters are sequentially numbered and come complete with a certificate.
Influence of temperature
The uncertainty of the certified measurement results is only valid for measuring temperatures as stated on the certificate. It is recommended to store the filters after use at room temperature in their storage case in a dry, dust-free environment.
For reasons of safety and especially with the cells containing liquids, take care not to expose them to temperatures below 0 °C or above 50 °C when storing and during transportation.
Other factors influencing the measurement
Dirt and dust as well as damage (scratches, blemishes) to the polished surfaces can considerably affect the measured values. Store the filters in the case and avoid any contamination of the polished windows. There should always be a recalibration associated with the cleaning of the standards.
Safety instructions
The filters containing liquids carry a label on one side with the chemical formula of the substances contained inside. If a filter breaks, please follow the corresponding safety instructions (e.g. safety data sheet).
Preparing for a measurement
Because of the variety of possible designs of spectrophotometers the application of a calibration standard for checking an instrument can only be given in general terms.
The spectrophotometer is switched on about half an hour before starting the measurements in order to achieve a constant instrument temperature (please follow the manufacturers’ instructions). The measurement should be carried out in a room with low humidity and the temperature which is given on the filters certificate.
The filters fit into cell holders for standard cells with 10 mm light path. They should always be placed in the cell holder in the same orientation, i.e. with the Hellma logo pointing towards the light source. The centre of the light beam should pass through the filter always at the same height in the lower third. When using single-beam photometers and especially diode array photometers connected to a separate cell holder via a fibre-optic cable, you should also consider that any stray radiation or vibrations (moving the fibre-optic cables) may affect the measurements.
