are short connecting pipes made of Poly- EtherEtherKetone which are glued into flow-through cells. PEEK is a chemically resistant, pressure resistant synthetic material with good mechanical characteristics. It is often used as an alternative to stainless steel.

mainly is the designation for the permanent or sometimes also the reversible discolouration of certain glasses under the influence of radiation with a high UV percentage. This discolouration is combined with a reduction of the transmission in the transmission range.

In the broadest sense, a photometer is any device used to measure light intensity. With reference to industrial photometry, it is the general term for instruments that measure absorption, fluorescence, and scattered light intensity. In all cases, the objective is to expose the medium in question to light and then to measure the intensity of the light resulting from the corresponding phenomenon.

Measurement of light intensities using photometers. In the field of analysis, a distinction is made between the measurement of absorption, of scatter (scattered light) and of fluorescence.

Polarimeter cells and cells for the measurement of circular dichroism must be free from stress birefringence. This is checked by measuring the empty cell in a polarimeter. Cells with a rotation of the polarisation plane of less than 0.01° are designated as stress-free.

For light waves, the direction of oscillation of the electric field strength is perpendicular to the direction of propagation of the wave (transverse wave). Most light sources emit light with no preference for a certain direction of oscillation. Polarisers help to separate a certain oscillation plane from the mixture of different planes. The result is linearly polarised electromagnetic waves.

Light consisting of several wavelengths. The light from the sun and artificial light sources (exception: laser) is polychromatic. The spectral distribution (spectrum) indicates the relative intensity of the individual wavelengths present. The wavelength range is called bandwidth: Wideband light appears whitish, narrowband light coloured (monochromatic light).

The standards offered by Hellma to check photometers are measuring devices certified in compliance with ISO 9001:2000 that must be traceable to international or national primary standards. Such primary standards can be bought (from the NIST) or calibrated (by the PTB).

are used to measure the refractive indices of liquids. The deflection of a ray of light as it traverses a prism depends on the refractive index of the prism material. For this reason, these cells are designed as hollow prisms.

PolytEtraFluorEthylene is resistant to almost all chemicals. Operational temperature range from –200 °C to +300 °C. The surface is not adhesive.

is a glass manufactured by the company Corning, USA and like Duran, is a pure borosilicate glass having a low sensitivity to temperature changes. It conforms to the standard ISO 3585 like Duran.