NIVELCO AnaCONT LE-100, Инструкция по установке и программированию, Страница: 5 / 61

BKI 11 ATEX 0012 X

le00100a0600p_05

5 / 60
Thank you for choosing a NIVELCO instrument.
We are sure that you will be satisfied throughout its use!
1. INTRODUCTION
1.1. A
PPLICATION
The AnaCONT compact transmitters, liquid analytical instruments are suitable for high precision measurement and transmission of acidity or alkalinity - pH
(Hydrogen ion concentration) value -, reducing and oxidizing capability - ORP (Oxidation Reduction Potential) value -, or Dissolved Oxygen content of process
water, wastewater, surface water, ground water and drinking water. These measurements can be widely used in industrial practice and could be of great
relevance. In the field of environmental protection or sewage treatment, instruments like that are suitable for measuring the concentration of hazardous
substances (chromium, cyanide). In chemical- and pharmaceutical industry, high precision measurement has utmost importance in the aspect of the technology
(e.g. solvent feed), in many cases it is quality specification standard.
1.2. O
PERATION PRINCIPLE
The intelligent signal processing of the electronics calculates the output signal from the voltage output values of the
electrode and the temperature probe, and compensates it to 25
°
C. This value composes the basis of all output
signals of the instrument.
1.2.1. Characteristics of an ideal pH electrode
The pH electrode immersed into the measured liquid measures a voltage value which is proportional to the hydrogen
ion concentration of the liquid.
 0mV output at neutral pH value (pH=7.00)
 Positive voltage output in acidic liquids (pH<7)
 Negative voltage output in alkaline liquids (pH>7)
 Total measuring range is 0-14pH
 -59.16mV/pH (Nernst potential) slope at 25 °C

The temperature dependency of the Nernst potential is -0.001984 mV / °C.
600
500
400
300
200
100
0
100
200
300
400
500
600
100° C (74.04 mV/pH)
25° C (59.16 mV/pH)
0° C (54.20 mV/pH)
2 4 6 8 10 12 14
1 3 5 7 9 1 1 13
Because the pH electrodes in deed are not ideal (their properties depend on the design of the electrode, manufacturing tolerances and most of all the age of the
electrode) the parameters differ from the given values above. To achieve reliable pH measurement and accuracy these electrodes must be calibrated from time
to time. The time interval between two calibrations depends on the application conditions where the pH probes are used. Calibration of pH electrodes means
offsetting the displayed value (7.00pH) when gauging neutral buffer solution, and adjusting the slope (pH/mV) by measuring buffer solutions with other pH value
(usually with 4.00pH and 10.00pH value) by adjusting the displayed value to exact 4.00 and 10.00pH, respectively.