EUTECH INSTRUMENTS WP PCD 650 Manuál s instrukcemi stáhnout pdf (Strana 113)

Instruction Manual PCD 650

105

The PCD 650 series meter not only measures conductivity readings from micro or

milli Siemens but also reads resistivity (Ohms, kOhms and MOhms), TDS (ppm and

ppt), and salinity (ppt).

The salinity scale which ranges from 0 to 80 ppt is a measure of all salts, not just

sodium chloride. This scale was originally devised for seawater, and is based on

seawater at 15 degrees Centigrade has a conductivity equivalent to that of a

potassium chloride solution of a known concentration. This solution (0.44 molar) is

defined as having a salinity of 35 ppt.

Note: ppm = parts per million, ppt = parts per thousand, 1000 ppm = 1 ppt

The total dissolved solids scale approximates the ppm TDS in surface waters by

multiplying the conductivity of a sample by a factor, 0.66.

Some users prefer the use of resistivity units to describe their water, particularly

where high purity water is involved. The unit most often used to describe resistivity is

megohm•cm., which is simply the reciprocal of conductivity (µS/cm). The chart below

shows the relationship between these units.

Conductivity, µS/cm Resistivity, megohm. cm

0.056 18.0

0.1 10.0

1.0 1.0

2.5 0.4

10.0 0.1

Conductivity and Temperature

Conductivity in aqueous solutions reflects the concentration, mobility, and charge of

the ions in solution. The conductivity of a solution will increase with increasing

temperature, as many phenomena influencing conductivity such as solution viscosity

are affected by temperature.

The relationship between conductivity and temperature is predictable and usually

expressed as relative % change per degree centigrade. This temperature coefficient

(% change per degree) depends on the composition of the solution being measured.

However, for most medium range salt concentrations in water, 2% per degree works

well. Extremely pure water exhibits a temperature coefficient of 5.2%, and

concentrated salt solutions about 1.5%.

This meter permit you to enter the temperature coefficient which best suits your

sample and use an ATC probe to automatically temperature compensate back to the

chosen reference temperature.

It is important to choose an electrode with an appropriate cell constant. The

following table lists the optimum conductivity ranges for electrodes with cell

constants of 0.1, 1, and 10.

Cell

Constant

Optimum Conductivity Range,

2-cell

Optimum Conductivity Range,

4-cell

0.1

0.5 to 200 µS/cm

Not Available

1.0

0.01 to 2 mS/cm 0.01 to 20 mS/cm

10.0 1 to 200 mS/cm 1 to 200 mS/cm

1 2 ... 108 109 110 111 112 113 114 115 116 117 118 119 120

Komentáře k této Příručce

Žádné komentáře

EUTECH INSTRUMENTS WP PCD 650 Manuál s instrukcemi Strana 113

Komentáře k této Příručce

Související produkty a manuály pro Měření, testování a kontrola EUTECH INSTRUMENTS WP PCD 650