Issuu on Google+

page_250_251.qxd

03.12.01

10:39

Seite 1

250

pH electrodes/conductivity measuring cells and their applications

Efflu ent s Gene amples ral a Aqua queous solu rium tions s Beer , frui t j uic Butte r, yo e, wine Subs ghurt, c hees tance e sc Emu lsion ontainin g s , egg a Emu queo white lsion us Earth s, part a q (su ueo Extre spension us me p ) H value Pene s (p trati Pene on meas H<1, pH> . in m tratio 13) nm eat Subs tance eas. in fr ui s con Galv taini t, vegeta anic bles ng h ydro Hot e sewage fluor lectr ic ac o lyte High id ly-vi s cous Solu aqu tions low i eous so Jams lutio n ion ns s Cosm etic p rodu Leath cts er m anuf Milk actur ing Rain wate r Brine Swim min Soap g pools s, de terge Aque nts ous Part- suspens aque ions ous Past susp ry, b ensio r ns Part- ead aque o us so Partl. >1 aqu 0% H Temp eous sol . <10 2 O eratu %H r e s Temp to +8 2O erat 0° TRIS ures to + C 1 buffe r sol 00°C ution s

Water analysis technology

Universal electrode, type 01 pH

+ + + 0 – – 0 0 0 0 – – – 0 – – – – – 0 0 0 0 + 0 0 – – 0 – 0 – 0 pH

Lab. electrode, type 02 pH

0 + + 0 – – 0 0 0 + – – 0 0 0 0 0 – 0 + 0 0 + + 0 0 – – 0 0 + 0 0 pH

Universal electrode, type 04 pH

+ + + 0 – – 0 0 0 0 – – – 0 – – 0 – – 0 0 0 + + 0 0 – – 0 – – – 0 pH/°C

Special electrode, type 05 pH

+ + 0 + – 0 + + + + – – 0 + – – 0 – – 0 0 + + + + + + – 0 0 – – 0 pH/°C

Penetration electrode, type 03 pH

0 0 0 0 + + + + + – 0 0 – 0 – + – + + – + – + 0 + + + 0 0 0 – – – pH

Robust penetr. electrode, type 13 pH

0 0 0 0 + + + + + – + + – 0 – + – + + – + – + – + + + + 0 0 – – – pH

Conduct. meas. cell, type 07 mS

+ + + + – + + 0 0 0 – – 0 + – – + – – + + + + + + 0 0 – 0 0 – – + mS/°C

Conduct. meas. cell, type 10 mS

+ + + + – + + 0 0 0 – – 0 + – – + – – + + + + + + 0 0 – 0 0 – – + mS/°C

Key:

+ suitable

0 suitable in certain cases

– not suitable

Example: cooking salt

An exact analysis of the contents in the laboratory will reveal the cause If cooking salt (NaCl) is added to of this alarming increase. Perhaps water the salt then breaks down into sewage was discharged into the its components (ions) Na+ and CI–. lake. Ions are charged particles and are responsible for the electrical Testo conductivity measuring resistance of the water. systems guarantee problemfree conductivity The conductivity provides informeasurement due to: mation on the total number of dissolved, charged components. What is conductivity? – a robust and user-friendly handheld instrument with simulFor electric conductivity electrical If, for example, the conductivity in taneous display of conductivity resistance is measured between two a lake has increased during a (referred to reference temperaelectrodes e.g. in a liquid. specific time the number of ture) and the temperature of the particles dissolved has also product being measured The lower the resistance the higher increased. the conductivity and vice versa. – the adaptability of the measuring Substances such as salt dissolved system to different measuring in water lower the electrical solutions on account of its resistance thus increasing adjustable temperature conductivity. coefficient Analytical instruments are only as accurate as the sensor used to perform the measurements. When measuring pH or conductivity only those probes suited to the particular substance can guarantee an accurate measured value.

– a robust measuring cell with 4 electrode measuring technology to protect from disturbing influences caused by polarisation effects

– fully automatic temperature compensation with the help of a temperature sensor integrated in the measuring cell – the display and documentation of measured and calibrated data

Conductivity measuring cells The 4 electrode measuring technology in our sensors enables an extensive measuring range to be covered with only one measuring cell. It also prevents the measured values becoming distorted by the formation of physical coatings, such as in waste water for example, ensuring accurate results every time. 4 electrode cells do not require replating unlike 2 electrode cells which means they have an almost unlimited lifetime.


page_250_251.qxd

03.12.01

10:39

Seite 2

251

Why you should choose water analysis instruments from Testo pH electrodes

Definition of the pH value

In conventional electrodes suspensions and emulsions as well as solutions containing proteins or sulphides can block the very many small pores in the diaphragm. The Single Pore Diaphragm, sensor type 05 pH, has proved to be highly effective for such critical applications. It consists of a single large pore which cannot become blocked due to the wide diameter of the pore. Quick response times and correct measured results are therefore guaranteed.

pH is the abbreviation of the Latin expression “pondus hydrogenii” (pondus = pressure, hydrogenium = hydrogen).

The hole diaphragm, type 03, is ideal for accurate measurements in solids or semi-solids (e.g. food). It consists of a very large “pore” therefore offering the advantages mentioned above in substances such as meat or cheese.

It is therefore a measure for the activity of the hydrogen ions in a substance. The activity is connected directly to its acidic, neutral or alkaline character.

Examples of the pH values of everyday substances acidic 0

1

neutral 2

3

4

5

6

7

alkaline 8

9

10 11 12 13 14

Ion free water 1M NaOH Lime water

Sour milk, yoghurt Lemon juice Gastric juice

Suds Hard well water

New robust pH penetration probe for testo 230 • Ergonomic handle design makes • Greater penetration power possible. your work easier. • The new T-handle design prevents buckling.

• Robust 5 mm cable with PUR coating.

• Short response time. Not affected by dirt thanks to hole diaphragm. With food• Cardanic storage of tip in plastic proof electrolyte. coating. Bending forces on tip do not pose a problem. Less chance of breaking glass! Patent pending. • pH glass embedded in breakproof plastic sleeve.


Water Analysis