Hach-Lange POLYMETRON 8398 User Manual

Document Number 221=183=098

POLYMETRON Model 8398

Inductive probe

USER MANUAL

April 2010, Version D

Restriction of hazardous substances (RoHS)

The European Union RoHS Directive and subsequent regulations introduced in member states and
other countries limits the use of six hazardous substances used in the manufacturing of electrical and
electronic equipment.

Currently, monitoring and control instruments do not fall within the scope of the RoHS Directive,
however Hach Lange has taken the decision to adopt the recommendations in the Directive as the
target for all future product design and component purchasing.

Note: The following only applies to exports of this product into the People’s Republic of China.

Conductivity plastic sensor
(8310, 8311, 8312)

Conductivity stainless
steel sensor (8314, 8394)

Digital sensor PCB O O

Glass electrode O O

O

OO

O:

X:

Inductive Probe 8398

Table of contents

1. INTRODUCTION................................................................................................ 3

1.1 General ....................................................................................................................3

1.2 Probes...................................................................................................................... 3

2. OPERATING PRINCIPLE.................................................................................. 4

2.1 Conductivity reminder ..............................................................................................4

2.2 Principle of inductive technology.............................................................................. 5

3. TECHNICAL SPECIFICATIONS ....................................................................... 6

3.1 Specifications...........................................................................................................6

3.2 Compliance ..............................................................................................................7

4. PROBE START-UP ........................................................................................... 7

4.1 Cable connection .....................................................................................................7

4.2 Use with a 8921 conductimeter................................................................................ 8

4.3 Use with a 9125 conductimeter................................................................................ 9

5. PROBE CALIBRATION..................................................................................... 9

6. INSTALLATION PRECAUTION ...................................................................... 11

7. ACCESSORIES ............................................................................................... 13

7.1 Probe 8398.2, 2" clamp model (08398=A=2000)...................................................13

7.2 Probe 8398.3, DIN 11851 / DN50 dairy connection model (08398=A=3000) ........14

7.3 Probe 8398.5, 1" threaded model gas ...................................................................16

8. MAINTENANCE............................................................................................... 18

9. PRECAUTIONARY LABELS........................................................................... 19

10. CHEMICAL RESISTANCE TABLE ................................................................. 20

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Inductive Probe 8398

1. INTRODUCTION

1.1 General

The 8398 range of probes makes use of inductive technology, which is particularly
recommended for corrosive and soiling uses, making use of conductivity or
concentration measurements. The main uses are as follows:

- Determination of solution concentrations: in-place cleaning, regeneration of
resin in water processing plants, surface treatment.

- Accurate interface control in conduits: in-place cleaning in the food and
pharmaceutical industries.

- Waste water testing: industrial and town sewerage plants.

1.2 Probes

WARNING: Non-removable cable!

8398.2 8398.3 8398.5
2''clamp DN50 dairy connection 1'' Gas

3

Inductive Probe 8398

D

2. OPERATING PRINCIPLE

2.1 Conductivity reminder

Electrolytic conductivity refers to the ability of a liquid to conduct an electrical current (conductivity is
the opposite of resistivity). In metals, the electrical current flows by electron displacement, in liquids it
flows by ion transport. The conductivity of a solution is dependent both upon the solution’s ionic
concentration and temperature.

To obtain a solution's actual conductivity (in S.cm-1), it is necessary to multiply the
measured conductance 1/R (in S) by a coefficient dependent solely upon the
geometry of the probe and termed "cell or K constant", expressed in cm

-1

.

K

C (S.cm

R

-1)

In order to allow the comparison between measurements made at different
temperatures, this measurement needs to be brought back to a

temperature

(generally 25 °C). This temperature dependency can be easily

reference

expressed in the form of relative variation in degrees Celsius. It is referred to as the
temperature coefficient (D).

C

= C T [1 + D (T - T

Tref

)]-1

ref

C

: Conductivity compensated to the reference temperature

Tref

C

: Conductivity measured at T

T

T

: Reference temperature (generally 25 °C)

ref

: Temperature coefficient of the solution (% / °C)

Examples:

Product Soda (NaOH)

5 %

D :

2.01 1.45

Nitric acid (HNO

10 %

)

3

REMARK:

1 S = 1000 mS (R = 1 :)
1 mS = 1000 μS (R = 1 k:)

4

Inductive Probe 8398

x

2.2 Principle of inductive technology

1 : Receiver
2 : Oscillator
3 : Cables
4 : Thermoplastic insulator
5 : Receiver
6 : Transmitter
7 : Induced current

The 8398 probes are made up of two coils that are completely insulated from the
process:

x The primary (or transmitter) coil, supplied with alternating voltage, produces an

alternating electromagnetic field that generates an electrical current in the solution.

x The secondary (or receiver) coil detects the size of the weak current induced by

the movement of ions in the solution.

The absence of contact between the electrical part and the solution (magnetic
coupling) provides a large number of advantages compared to the traditional
technique using metallic electrodes:

No polarisation and hence a broad measurement range.

x High chemical and mechanical resistance.
x Possibility of performing measurements in soiling products.
x Perfectly hygienic design.

5

Inductive Probe 8398

3. TECHNICAL SPECIFICATIONS

3.1 Specifications

Measurement range 0 to 2000 mS/cm

Precision

r 2 % of the displayed value or r 0.004 mS/cm

Conductivity response < 1 s

Temperature response T 50 % = 20 s

T 90 % = 2 mn

Cell constant K = 2.35 cm-1

Roughness Ra < 0.5 μm (roughness certificate on request,

Ref.: 08398=T=1111)

Chemical resistance Our mono-block probe is made from PEEC

(poly ether ether Ketone), whose chemical
resistance is summarised in the table §9.

WARNING: PEEC is not resistant to high
concentrations of oxidative acids (nitric and
sulphuric acid > 70 %, etc.) In the case of
probe 8398.5, one must consider the other
materials in contact with the process (EPDM or
VITON gaskets, PP or 316 stainless steel
extension, etc.).

Mechanical resistance PEEC possesses a flexion temperature

(pressure: 18 bars) of approximately 300 °C.

In the case of probe 8398.5, take account of
extensions, if any.

Heat resistance PEEC is a polymer that is particularly well-

suited to sterilisation, it can therefore withstand
temperatures of 140 °C.

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