Hach Polymetron 9526 Basishandbuch Seite 8

• Long cables leading to capacitive effects not taken into account during controller electronic
calibration
Figure 1 Front and rear view
1 Controller
2 Protective hood
3 Accessory drawer
4 IP 67 socket for analog output
5 IP 67 socket for calibration
The unit is made up of a conductivity controller (1) and a flow chamber containing a high precision
conductivity sensor, all contained in a high resistant ABS casing. A hood (3) protects the display
panel whose backlit surface provides optimum visibility. A drawer (7) is used for storing accessories
and documentation. The unit should be placed on a flat surface, preferably in a clean and dry
environment.
Accuracy and benefits
The system is a certified standard guaranteeing a high degree of measurement accuracy conforming
to all the required standards used in pure water conductivity measurements (ASTM D 1125, D
5391 and USP).
Accurate electrical calibration
The measurement of conductivity requires the use of a high frequency current to minimize electrolytic
reactions at the surface of the electrodes. In addition, the use of a long cables for measurements can
generate a capacitance causing errors when measuring the value of a resistance.
The Polymetron 9526 avoids this problem by performing an electrical calibration at the end of the
product's conductivity sensor cable using a certified electrical resistance (precision ± 0.1%).
Accurate temperature measurement
Accurate temperature measurement is essential in ultra pure water as the variation in conductivity is
very high (ratio of around 5.2%/°C). The Polymetron 9526 uses a class "A" temperature sensor
mounted at the end of the internal electrode. Ambient temperature has no effect as the sensor and
internal flow chamber are thermally insulated.
To eliminate any electrical resistance, an electrical calibration at the end of the cable using precision
resistors has been performed in our factory . A calibration is then performed with a certified
8 English
6 IP 67 socket for electric power
supply
7 Lead seal
8 Waterproof feet
9 Product type label
10 Calibration label
11 Sample inlet
12 Sample outlet
13 Analog output cable (option)
14 Cable to external controller
15 Power supply connector