defr Glossar

In the broadest sense, a photometer is any instrument used to measure light intensity. As applied in industrial photometry, “photometer” is the general term covering instruments for detecting

in liquids and gases.

The objective is the same in all cases: to expose the medium in question to light and then to measure the intensity of the light (light intensity) produced by the respective phenomenon using various measuring methods. Figure 35 shows the principle of the single-beam method as it is used for absorption measurement.

Single-beam method with light source (1), flow cell (2), photo receiver (3) and amplifier (4)
Fig. 35: Single-beam method with light source (1), flow cell (2), photo receiver (3) and amplifier (4)

The light source transmits a light beam through the medium in the flow cell and the photoreceiver measures the intensity of the remaining light. After being amplified in the amplifier, an electrical signal is delivered as the absorption reading.

The purpose of the measurement is to detect how much the light intensity is attenuated by the substance in the flow cell. Besides this sought variable, however, the reading will also be affected by the luminosity of the light source and the sensitivity of the photoreceiver. Because the properties of these components vary as a result of aging and fluctuations of the supply voltage and the ambient temperature, single-beam photometers are inherently unstable and require frequent recalibration.

This may be feasible for intermittent measurements in the laboratory, but it is clearly unacceptable for industrial duty and continuous measurement. One way to eliminate the effect of light source fluctuations is to use the dual-beam method as shown in Fig. 36.

Dual-beam method with two photodetectors measurement beam (1) and reference beam (2)
Fig. 36: Dual-beam method with two photodetectors measurement beam (1) and reference beam (2)

With this configuration, a semi-transparent mirror produces two beams: a measurement beam, which passes through the sample and strikes the first photoreceiver, and a reference beam that goes straight to the second receiver.

Because the reading represents the ratio of the two, fluctuations of the light source's luminosity have no effect on the results.

Index

Contact distribution partner

{{selectedCountry.Name}} {{country.Name}}

Please select your businessarea

{{ba.Name}}

Please select

{{area.Name}}

Please select your businessarea

{{ba.Name}}
{{selectedCountry.Name}} {{country.Name}}
{{vm.getBusinessAreaStringByVendor(vendor)}} {{area.Name}}
{{vm.getBusinessAreaStringByVendor(vendor)}}
René Gehri
Water, Beverages & Food, Industrial Processes
Florian Bodmer

Contact headquarters

Felix Joller
Sales Manager ScrubberGuard
Öffnungszeiten:
Montag–Freitag 08:00–12:00 und 13:30–17:00
Feiertage & Betriebsferien:
Ostern: 07.–10. April 2023, Auffahrt: 18. Mai 2023, Pfingstmontag: 29. Mai 2023, Fronleichnam: 08. Juni 2023, Bundesfeiertag: 01. August 2023, Maria Himmelfahrt: 15. August 2023, Allerheiligen: 01. November 2023, Maria Empfängnis: 08. Dezember 2023, Betriebsferien: 23. Dezember 2023 – 02. Januar 2024
Opening hours:
Monday–Friday 08:00am–12:00pm und 1:30pm–5:00pm
Public & company holidays:
Easter: 07.–10. April 2023, Ascension Day: 18. May 2023, Whit Monday: 29. May 2023, Corpus Christi: 08. June 2023, Federal Holiday: 01. August 2023, Assumption Day: 15. August 2023, All Saints Day: 01. November 2023, Conception of Mary: 08. December 2023, Company holidays: 23. December 2023 – 02. January 2024