Hach-Lange 1200-S User Manual

DOC023.52.03253

1200-S sc digital combined electrode

for pH and Redox

User Manual

02/2013 Edition 2A

Section 1 Specifications .............................................................................................................................................. 3

1.1 Technical data on the 1200-S sc - pH / ORP sensor................................................................................................. 3

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

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

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

2.3 Measuring principle ................................................................................................................................................... 5

2.3.1 pH measurement ............................................................................................................................................. 5

2.3.2 REDOX measurement ..................................................................................................................................... 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 the 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 (pH) ........................................................................................................................................... 17

5.6.1 Calibration using a buffer solution.................................................................................................................. 17

5.6.2 Calibration using two buffer solutions ............................................................................................................ 17

5.6.3 Calibration using a sample solution ............................................................................................................... 18

5.6.4 Calibration using two sample solutions.......................................................................................................... 18

5.7 Sensor calibration (REDOX).................................................................................................................................... 18

5.8 Sensor calibration (temperature) ............................................................................................................................. 19

5.8.1 Calibrating two sensors simultaneously ......................................................................................................... 19

Section 6 Maintenance ................................................................................................................................................ 21

6.1 Maintenance schedule............................................................................................................................................. 21

6.2 Cleaning the sensor................................................................................................................................................. 21

6.3 Changing electrode ................................................................................................................................................. 21

Section 7 Faults, causes, rectification ...................................................................................................................... 23

7.1 Error messages ...................................................................................................................................................... 23

7.2 Warnings ................................................................................................................................................................ 23

7.3 Important service data ............................................................................................................................................. 24

Table of contents

Section 8 Spare parts...................................................................................................................................................25

Section 9 Warranty and liability..................................................................................................................................27

Section 10 Contact.......................................................................................................................................................29

Appendix A ModBUS Register Information ..............................................................................................................31

Section 1 Specifications

1.1 Technical data on the 1200-S sc - pH / ORP sensor

Materials Stainless steel metal housing

Enclosure rating IP 68; stainless steel metal housing

pH measuring range 0 pH ... 14 pH

ORP measuring range –1,500 ... 1,500 mV

Temp. measuring range –5 °C ... 50 °C

Storage temperature Sensor and controller

pH / ORP response time <15s; T90

Temp. response time <2min; T90

pH measuring accuracy ± 0.02 pH

ORP measuring accuracy ± 1.2 mV

Temp. measuring accuracy ± 0.2 °C

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

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

Calibration, pH

Calibration, ORP One point, comparative measurement

Calibration, temp One point, comparative measurement

Max. immersion depth / pressure for the sensor

Maximum flow speed 4 m/s

Sensor interface MODBUS

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

One or two point, standard buffer solution (automatic), One or two point, comparative measurement

20 m / 2 bar over-pressure

Sensor cable 10 m, hard wired, polyurethane

Sensor weight <1 kg

Sensor dimensions (Ø × L) 42 × 504 mm

Fastening

Service life measuring electrode Approx. 1 year

Sensor power < 7 W

• Immersed pipe

• Chain

Specifications are subject to change without notice.

Specifications

Section 2 General information

2.1 General handling instructions

CAUTION! The sensor will only work correctly when the tip of the probe is completely immersed in liquid. The measuring probe must not be stored dry for more than approx. 10 minutes or protrude from the medium to be measured. Use the transport cap during the installation of the sensor, during maintenance and when transporting, and fill the cap with 3 mol. KCl or pH 4 buffer solution.

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.

2.2 Applications

The sensor makes it possible to simply and exactly measure pH directly in aqueous solutions.

2.3 Measuring principle

2.3.1 pH measurement

Typical applications include

• Inlet and / or outlet of a sewage treatment plant

• Activated sludge tanks or

• Surface water (rivers, streams or lakes).

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

pH is the negative logarithm of the hydrogen ion activity as well as a measurement of the acidic or alkaline content of a solution:

pH = –log10 [aH+]

The pH value is normally measured using a glass electrode and a reference electrode. In this case the glass electrode acts as the transducer that converts the chemical energy (hydrogen ion activity) into electrical energy (measured in millivolts). The reaction is symmetrical and the electrical circuit is closed by the ion flow from the reference solution to the test solution.

Together with the reference solution, the electrode generates a voltage (EMF). The magnitude of the voltage is dependent on the type of reference electrode, the internal design of the glass electrode, the pH value of the solution as well as the temperature.

General information

This voltage is expressed by the following Nernst equation:

E = Eo – (2.3 RT/F)xlog a[H+] E = Eo – (gradient) xlog a[H+]

Where the following applies:

2.3.2 REDOX measurement

E Eo

R T a[H+]

EMF value of the cell

Zero voltage (isopotential) of the system (depends on the internal design of the glass electrode and reference electrode)

Gas constant

Temperature in Kelvin

Activity of the hydrogen ions (corresponds to the concentration of the hydrogen ions)

Faraday constant

With every unit change in the pH (or decimal change in the ion concentration), the EMF produced by the pair of electrodes changes by 59.16 mV at 25 °C. This value is termed the gradient of the electrode.

The pH electrode pair is calibrated using solutions with a known and constant hydrogen ion concentration. These solutions are termed buffer solutions. The buffer solutions are used for the calibration of both the electrode isopotential and the gradient.

In a Redox system the measurements are made using a balanced instrument that comprises a Redox electrode and a reference electrode. The potential to be measured is termed the Redox potential and depends on the relationship between the activities of the two components of a Redox system and the number of electrons transferred. In many cases, the pH value of the solution also affects the potential.

The half-cell potential εB of the reference electrode has a large effect on the potential E of the measuring chain. To rectify this effect, the potential of the measuring electrode can be referred to the hydrogen electrode. If εB is the halfcell potential of the reference electrode used, the calculation is performed using the following formula:

ε(H) = E + εB

ε(H) εB

EMF value of the cell

= =

Half-cell potential

Such standardised Redox potentials provide a certain amount of information on the oxidisation or reduction potential of a Redox system. Increasing positive values indicate increasing oxidation energy. The more negative the potential, the higher the reduction energy. The area that is of interest in practice is between +1500 and –1000 mV.

Standard potentials for a Redox system for aOx = aRed (a=activity) and for pH = 0 can be defined. This is turn corresponds to a standardised hydrogen ion activity of aH+ = 1 mole per litre.

The stability and ability to reverse a Redox system have a significant effect on the reproducibility of the Redox potential measured.

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 (EU directive 2002/96/EC), 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.

3.4 Chemical safety measures

CAUTION! Reference and standard solutions are used for the calibration. Some of these compounds are toxic or caustic.

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.

Physical contact with a calibration solution and inhalation of vapours from a calibration solution are to be avoided or limited to an absolute minimum.

3.5 Safety measures related to the flow of sample

The assessment of the possible hazards from the individual sample flows is the responsibility of the user. Suitable safety measures are to be taken to avoid any unnecessary contact with a flow of sample of unknown composition in relation to the hazards due to traces of chemicals, radiation or biological effects.