Hach-Lange 3798-S sc User Manual

DOC023.52.03252

3798-S sc

Digital inductive conductivity sensor

User Manual

02/2013 Edition 2A

Section 1 Technical data............................................................................................................................................... 3

1.1 Technical data for the 3798-S sc conductivity sensor .............................................................................................. 3

Section 2 General information ..................................................................................................................................... 5

2.1 General handling instructions .................................................................................................................................... 5

2.2 Applications ............................................................................................................................................................... 5

2.3 Basic principles.......................................................................................................................................................... 5

2.4 Measuring principle ................................................................................................................................................... 6

Section 3 General safety instructions ......................................................................................................................... 7

3.1 Possible sources of hazards...................................................................................................................................... 7

3.2 Safety symbols .......................................................................................................................................................... 7

3.3 Electrical safety measures and fire prevention measures ......................................................................................... 8

3.4 Chemical safety measures ........................................................................................................................................ 9

3.5 Safety measures related to the flow of sample.......................................................................................................... 9

Section 4 Installation....................................................................................................................................................11

4.1 Connecting sensor cable ......................................................................................................................................... 11

4.2 Mechanical sensor installation................................................................................................................................. 12

4.2.1 Installation dimensions .................................................................................................................................. 12

Section 5 Operation..................................................................................................................................................... 15

5.1 Operating the sc controller ...................................................................................................................................... 15

5.2 Sensor setup ........................................................................................................................................................... 15

5.3 Sensor data logger .................................................................................................................................................. 15

5.4 The commands under SENSOR DIAG.................................................................................................................... 15

5.5 The commands under SENSOR SETUP ................................................................................................................ 16

5.6 Sensor calibration (conductivity) ............................................................................................................................. 17

5.6.1 Calibration in air (ZERO CAL)........................................................................................................................ 17

5.6.2 Calibration in air (ELECTRIC. SPAN) ............................................................................................................ 17

5.6.3 Calibration in the process (PROCESS SPAN)............................................................................................... 17

5.7 Adjusting the Temperature ...................................................................................................................................... 18

5.8 Calibrating two sensors simultaneously .................................................................................................................. 18

Section 6 Maintenance ................................................................................................................................................ 19

6.1 Maintenance schedule............................................................................................................................................. 19

6.2 Cleaning the sensor................................................................................................................................................. 19

Section 7 Faults, causes, rectification ...................................................................................................................... 21

7.1 Error messages ...................................................................................................................................................... 21

7.2 Warnings ................................................................................................................................................................ 21

7.3 Important service data ............................................................................................................................................. 22

Section 8 Spare parts .................................................................................................................................................. 23

Section 9 Warranty and liability ................................................................................................................................. 25

Section 10 Contact ...................................................................................................................................................... 27

Appendix A ModBUS Register Information ............................................................................................................. 29

Table of contents

Section 1 Technical data

1.1 Technical data for the 3798-S sc conductivity sensor

Materials Stainless steel metal housing, PEEK

Enclosure rating IP 68; stainless steel metal housing

Storage temperature Sensor and controller

Cell constant K=2.35cm

Measuring range conductivity 250 µS/cm ... 2.5 S/

Temp. measuring range –5 °C ... 50 °C

Sensor operating temperature –20 °C ... 50 °C

Conductivity response time < 2 s; T90

Temp. response time <2min; T90

Conductivity measuring accuracy ± 1 % of the measured value displayed or ± 0.004 mS/

Temp. measuring accuracy ± 0.2 °C

Reproducibility < 0.2 %

Sensitivity ± 0.5 % of the end value of the measuring range

Sensor power < 7 W

Calibration

Max. immersion depth / pressure for the sensor

–20 °C ... 60 °C; 95 % relative humidity, non-condensing

–1

Zero value calibration in air. Fixed value calibration with defined resistance or with standard solution

20 m / 2 bar

Maximum flow speed 4 m/s

Sensor interface MODBUS

Sensor cable 10 m, hard wired, polyurethane

Sensor weight < 1 kg

Sensor dimensions (Ø × L) 43 × 370 mm

Fastening

• Immersed pipe

• Chain

Specifications are subject to change without notice.

Technical data

Section 2 General information

2.1 General handling instructions

Attention! The sensor will only work correctly when the tip of the probe is completely immersed in liquid. Ensure the tip of the probe always remains underwater even when the water level fluctuates.

2.2 Applications

CAUTION! Potential danger with contact with chemical/biological substances. Working with chemical samples, standards and reagents can be dangerous. Make yourself familiar with the necessary safety procedures and the correct handling of the chemicals before use and read and follow all relevant safety data sheets.

The sensor facilitates the straightforward and exact determination of the conductivity of soiled to heavily soiled aqueous solutions. The system is specially designed for use in municipal and industrial waste water.

2.3 Basic principles

Typical applications include

• Inlet and / or outlet of a sewage treatment plant

• Surface water if within the measuring range (> 250

Various different possible installations enable the system to be adapted to a very wide range of conditions.

The electrolytic conductivity is the ability of a liquid to conduct an electrical current (conductivity is the opposite of resistance). In metals, electrical currents are passed by the movement of electrons, in liquids by the movement of ions. The conductivity of a liquid depends on the one hand on the ionic concentration, on the other hand on the temperature of the liquid.

To obtain the real conductivity of the liquid (in measured geometry of the probe and that is called the "cell constant or K" (

To be able to make a comparison between the measurements made at different temperatures, the measurement must be converted to a reference temperature (as a rule 25 °C).

/R (in S) must be multiplied by a coefficient that depends on the

C= K/R (S/cm)

/cm), the conductivity value

µS

/cm).

General information

This temperature-dependence, expressed in [% / °C], is termed the temperature coefficient (α).

2.4 Measuring principle

= CT [1 + α (T – T

Tref

C C T α : coefficient of the liquid temperature (

: conductivity adjusted to the reference temperature

Tref

: conductivity measured at T

: reference temperature (as a rule 25 °C)

ref

)]

– 1

/°C)

The tip of the probe comprises two coils that are completely insulated from the surrounding medium.

Primary coil (transmitter):

An AC voltage is applied to the primary coil and produces an alternating electromagnetic field in the surrounding liquid. This magnetic field generates an electrical current in the liquid.

Secondary coil (receiver):

The secondary coil determines the current produced by the ion movements and calculates the conductivity of the liquid from the current.

1. Receiver

2. Oscillator

3. Cable

4. Insulation

5. Receiver coil

6. Transmitter coil

7. Field line

The electrical insulation between liquid and sensor (magnetic coupling) has advantages compared to the conventional method of using metal electrodes:

• no polarisation, for this reason the measuring range is larger

• high mechanical and chemical resistance

• possibility of taking measurements in soiled liquids

Section 3 General safety instructions

Prior to unpacking, commissioning or operating the instrument, read all of this manual.

Please pay particular attention to all instructions on hazards and safety. Otherwise there is a risk of serious injury to the operator or damage to the instrument, or pollution.

The sensor is only allowed to be installed and used as per the instructions in this manual.

3.1 Possible sources of hazards

During the operation or calibration of the sensor, there exist the following sources of hazards if the safety instructions are not observed:

• Potentially hazardous materials (buffer solutions, flow of sample)

In all circumstance observe the safety data sheets and the applicable health and safety instructions.

3.2 Safety symbols

This symbol, if present on the instrument, refers to information in the operating instructions on safe operation and / or instructions that provide safety information.

This symbol, if present on a housing or a protective cover, identifies the risk of an electric shock (which may under certain circumstances be fatal). Only personnel qualified for working on hazardous voltages are allowed to open the enclosure or remove the protective cover.

This symbol, if present on the instrument, identifies the location of a fuse or current limit.

This symbol, if present on the instrument, identifies a part that may become hot and must not be touched without taking precautions.

This symbol, if present on the instrument, indicates the presence of components that could be damaged by electrostatic discharge. Appropriate precautions are to be taken.

This symbol, if present on the instrument, indicates the presence of dangerous chemical substances. Chemicals are only allowed to be handled and maintenance on devices for supplying chemicals is only allowed to be performed by personnel qualified and trained for working with chemicals.

All stickers and labels on the instrument are to be observed. Otherwise injuries, pollution or damage to the instrument may occur.

General safety instructions

This symbol, if present on the instrument, indicates that safety glasses must be worn.

This symbol, if present on the instrument, identifies the location of the connection for the protective earth (ground).

As of 12 August 2005, electrical appliances marked with this symbol are no longer allowed to be disposed of in Europe in unsorted household or industrial waste. As per the applicable regulations, from this date on consumers in the EU must return old appliances to the manufacturer for disposal. This disposal is free of charge for the consumer.

Note: You can obt ain instructions on the correct disposal of all (marked and unmarked) electrical products that have been supplied or manufactured by Hach-Lange from your local Hach-Lange sales office.

3.3 Electrical safety measures and fire prevention measures

The following safety instructions must be observed during the installation and repair of cables that carry electrical power:

DANGER! Sensors and controller are designed for compliance with the U.S. and Canadian NEC as well as the European low voltage directive. No internal electrical or electronic parts are allowed to be modified in any way, as this could render the CE conformity void.

WARNING! Only qualified experts may perform the tasks described in this section of the manual, while adhering to all locally valid safety regulations.

• Prior to maintenance or repair of the instrument, isolate it from the power

supply.

• When making electrical connections, all applicable local and national regulations are to be met.

• The use of earth leakage trips is strongly recommended.

• The instrument must be correctly earthed for correct operation.

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