wtw inoLab Multi 720 Operating Manual
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wtw inoLab Multi 720 Operating Manual

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Operating Manual
inoLab
Multi 720
Measuring Instrument
for pH, Redox, Dissolved Oxygen
and Conductivity
ba75442e01
03/2004

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Summary of Contents for wtw inoLab Multi 720

  • Page 1 Operating Manual inoLab Multi 720 Measuring Instrument for pH, Redox, Dissolved Oxygen and Conductivity ba75442e01 03/2004...
  • Page 2 Copyright Weilheim 2004, WTW GmbH © Reprinting - even as excerpts - is only allowed with the ex- plicit written authorization of WTW GmbH, Weilheim. Printed in Germany.

  • Page 3: Table Of Contents

    Multi 720 Contents Overview ......87 1.1 Keypad ....... 88 1.2 Display .
  • Page 4 Contents Multi 720 4.7.2 Setting up the cell constant ..130 4.8 Setting up the temperature compensation TC 133 4.9 Configuration ......137 4.10 Reset .

  • Page 5: Overview

    Multi 720 Overview Overview The compact inoLab Multi 720 precision measuring instru- ment lets you perform pH, Redox, D. O., and conductivity measurements rapidly and reliably. The inoLab Multi 720 provides the highest degree of operating comfort, reliability and measuring safety for all applications.

  • Page 6: Keypad

    Overview Multi 720 Keypad Measuring instrument ON/OFF Select measuring mode Call up calibration procedure Activate/deactivate AutoRead Confirm inputs, start AutoRead Select measuring mode, increase values, scroll Select measuring mode, reduce values, scroll...

  • Page 7: Display

    Only connect probes to the instrument that cannot feed ex- cessive voltages or currents (> SELV and > circuit with cur- rent limiter). Almost all commercial electrodes - especially WTW electrodes - meet these requirements. On socket 4, use the WTW probe StirrOx G only.

  • Page 8: Operating Structure

    Overview Multi 720 1.4 Operating structure The following overview diagram shows which keys you have to press to select between the different measuring modes: Note When a D. O. probe or a conductivity measuring cell with temperature probe is connected, the measuring instrument recognizes the probe or measuring cell and automatically switches to the oxygen measuring mode or conductivity measuring mode last selected.

  • Page 9: Safety

    Multi 720 Safety Safety This operating manual contains basic instructions that you must follow during the commissioning, operation and main- tenance of the instrument. Consequently, all responsible personnel must read this operating manual before working with the instrument. The operating manual must always be available within the vicinity of the instrument.

  • Page 10: Authorized Use

    In this event, wait until the temperature of the instrument reaches room tem- perature before putting the instrument back into operation. Caution The instrument is only allowed to be opened by personnel authorized by WTW.
  • Page 11 Multi 720 Safety Safe operation If safe operation is no longer possible, the instrument must be taken out of service and secured against inadvertent op- eration. Safe operation is no longer possible if: the instrument has been damaged in transport the instrument has been stored under adverse conditions for a lengthy period of time the instrument is visibly damaged...
  • Page 12 Safety Multi 720...

  • Page 13: Commissioning

    (see chapter 7 T ECHNICAL 1 Insert the plug (1) into the socket (2) of the meter. 2 Connect the original WTW plug-in power supply (3) to an easily accessible mains socket. Note If a stirrer is operated via the measuring instrument, it is...
  • Page 14 Commissioning Multi 720 Scope of delivery Laboratory measuring instrument, inoLab Multi 720 Operating manual and short manual 4 x type AA Mignon 1.5 V batteries...

  • Page 15: Operation

    Multi 720 Operation Operation Switch on the instrument 1 Place the instrument on a flat surface and protect it against intense light and heat. 2 Press the key. The display test appears briefly on the display. The instrument then switches automatically to the measuring mode.

  • Page 16: Measuring The Ph Value/Redox Voltage

    Operation Multi 720 Measuring the pH value/Redox voltage Preparatory Perform the following preparatory activities when you want activities to measure: 1 Press the key repeatedly until the pH/Redox measurement appears on the display. 2 Connect the electrode to the instrument. 3 Adjust the temperature of the buffer or test solutions or measure the current temperature if the measure- ment is made without a temperature probe.
  • Page 17 Multi 720 Operation The temperature measurement is absolutely essential for a reproducible pH measurement. If the measurement is made without a temperature probe, proceed as follows: 1 Determine the current temperature using a thermo- meter. 2 Press and hold down the key and set up the tem- perature using Note...

  • Page 18: Measuring The Ph Value

    Operation Multi 720 4.2.1 Measuring the pH value 1 Perform the preparatory activities according to sec- tion 4.2. 2 Immerse the pH electrode into the test sample. 3 Press the key until pH appears in the status display. The pH value appears on the display. AutoRead AR The AutoRead function (drift control) checks the stability of (Drift control)
  • Page 19 Multi 720 Operation Note The current AutoRead measurement (with acceptance of the current value) can be terminated at any time by pressing . It is only possible to change to another measuring mode after AutoRead has been terminated. 4.2.2 Measuring the Redox voltage The instrument can measure the Redox voltage (mV) of a solution when connected with a Redox electrode, e.g.
  • Page 20 Always calibrate after connecting another pH electrode. You can choose between 3 calibration procedures: AutoCal TEC is specially adapted to the WTW technical buffer solutions as a fully automatic two-point calibration. The buffer solu- tions are automatically recognized by the instrument.
  • Page 21 Multi 720 Operation Display Asymmetry Slope [mV] [mV/pH] -15 ... +15 -60.5 ... -58 -20 ... +20 -58 ... -57 -25 ... +25 -61 ... -60.5 -57 ... -56 -30 ... +30 -62 ... -61 -56 ... -50 Clean the electrode accord- ing to the electrode manual <...

  • Page 22: Autocal Tec

    Operation Multi 720 4.3.1 AutoCal TEC Use any two of the WTW technical buffer solutions for this procedure (pH 2.00, 4.01, 7.00, or 10.01). Note The calibration for pH 10.01 is optimized for the WTW tech- nical buffer solution TEP 10 Trace or TPL 10 Trace. Other buffer solutions can lead to an erroneous calibration.
  • Page 23 Multi 720 Operation 5 Thoroughly rinse the electrode with distilled water. 6 If necessary, set the temperature of the second buffer solution by pressing 7 Submerse the electrode in the second buffer solution 8 Press the key. AR flashes on the display. The electrode voltage (mV) appears on the display.

  • Page 24: Autocal Din

    Operation Multi 720 4.3.2 AutoCal DIN Use two different DIN buffer solutions (type A, C, D or F with the pH values 1.679, 4.006, 6.865, 9.180) for this procedure. Note Steps 2 and 6 are not required if you use a temperature probe.
  • Page 25 Multi 720 Operation 6 If necessary, set the temperature of the second buffer solution by pressing 7 Submerse the electrode in the second buffer solution. 8 Press the key. AR flashes on the display. The electrode voltage (mV) appears on the display. As soon as a stable value is recognized, AR disap- pears.

  • Page 26: Concal

    Operation Multi 720 4.3.3 ConCal Two-point Use two buffer solutions for this procedure: calibration pH 7.0 ± 0.5 any other buffer solution Note Steps 2 and 6 are not required if you use a temperature probe. 1 Press the key repeatedly until the ConCal func- tion display appears.
  • Page 27 Multi 720 Operation 8 Thoroughly rinse the electrode with distilled water. 9 If necessary, set the temperature of the second buffer solution by pressing 10 Submerse the electrode in the second buffer solution. 11 Press the key. The second measured pH value appears on the dis- play.
  • Page 28 Operation Multi 720 Single-point Use any buffer solution for this rapid method. The calibration calibration will be the more exact the nearer the pH value of the buffer solution is to that of the test sample. Note Only the electrode asymmetry is determined in single-point calibration.

  • Page 29: Measuring The Dissolved Oxygen

    Multi 720 Operation Measuring the dissolved oxygen The following parameters can be measured: Oxygen concentration Oxygen saturation Oxygen partial pressure The measuring instrument has the following functions: AutoRange (automatic selection of the measuring range), AutoRead (drift control) to check the stability of the mea- suring signal.

  • Page 30: Oxygen Concentration

    Operation Multi 720 4.4.1 Oxygen concentration When measuring the concentration in test samples with a salt content of more than 1 g/l, a salinity correction is re- quired. Note How to enter the current salt content is described in section 4.5.2 on page 120.

  • Page 31: Oxygen Saturation

    Multi 720 Operation 2 Press and hold down the key and with switch off the salinity correction function. Sal disappears from the display. 4.4.2 Oxygen saturation To measure the oxygen saturation proceed as follows: 1 Perform the preparatory activities according to sec- tion 4.4.

  • Page 32: Oxygen Partial Pressure

    Operation Multi 720 4.4.3 Oxygen partial pressure To measure the oxygen partial pressure proceed as follows: 1 Perform the preparatory activities according to sec- tion 4.4. 2 Immerse the D. O. probe into the test sample. 3 Press the key until the oxygen partial pressure in mbar appears on the display.
  • Page 33 Multi 720 Operation 5 If necessary, start the next AutoRead measurement by pressing 6 To terminate the AutoRead function: Press Note The current AutoRead measurement (with acceptance of the current value) can be terminated at any time by pressing . It is only possible to change to another measuring mode after AutoRead has been terminated.

  • Page 34: Calibrating For D. O. Measurements

    Operation Multi 720 Calibrating for D. O. measurements Why calibrate? D. O. probes age. This changes the slope of the probes. As a result, an inexact measured value is displayed. Calibration determines the current slope of the probe and stores it in the instrument.
  • Page 35 Multi 720 Operation Probe evaluation After the calibration, the instrument automatically evaluates the current status of the probe using the relative slope. The relative slope does not affect the measuring accuracy. Low values indicate that the electrolytic filling will soon be deplet- ed and the probe will have to be regenerated.

  • Page 36: Starting The Calibration

    Operation Multi 720 4.5.1 Starting the calibration To calibrate the instrument proceed as follows: 1 Connect the D. O. probe to the instrument. ® 2 Keep the OxiCal -SL air calibration vessel ready. Note The sponge in the air calibration vessel must be moist (not ®...
  • Page 37 Multi 720 Operation 6 As soon as a stable value is reached, AR stops flash- ing. Thus the calibration is finished and the probe symbol indicates the relative slope determined and the probe evaluation (see page 117). 7 With change to the measuring mode. Note Refer to chapter 6 W ...

  • Page 38: Entering The Salt Content (Salinity)

    Operation Multi 720 4.5.2 Entering the salt content (salinity) When measuring the concentration of test samples with a salt content of more than 1 g/l, a salinity correction is re- quired. For this, you have to determine and input the salinity of the test sample first.

  • Page 39: Measuring The Conductivity

    Multi 720 Operation Measuring the conductivity The following parameters can be measured: Conductivity/resistance (how to switch over, see section 4.9 C ONFIGURATION Salinity Total dissolved solids (TDS) The measuring instrument has the following functions: AutoRange (automatic selection of the measuring range), AutoRead (drift control) to check the stability of the mea- suring signal.
  • Page 40 Operation Multi 720 Checking the cell 3 Press the key repeatedly until LF CELL is constant displayed. 4 Press the key. The previously selected cell constant ist displayed, e. g. 0.475 cm 5 To return to the measuring mode: press the when the correct cell constant ist displayed.

  • Page 41: Conductivity / Specific Resistance

    The conductivity measuring cell has an integrated tempera- ture probe that always measures the current temperature of the test sample. If you want to use a WTW conductivity measuring cell with- out a temperature probe, you have to connect it with an adapter (available at WTW).

  • Page 42: Salinity

    Operation Multi 720 Specific resistance 4 Wait for a stable measured value. 4.6.2 Salinity To measure the salinity, proceed as follows: 1 Perform the preparatory activities according to section 4.6. 2 Immerse the conductivity measuring cell into the test sample. 3 Press the key repeatedly until Sal appears in the status line.
  • Page 43 Multi 720 Operation 4.6.3 TDS (total dissolved solids) To measure the TDS, proceed as follows: 1 Perform the preparatory activities according to section 4.6. 2 Immerse the conductivity cell into the test sample. 3 Press the key repeatedly until TDS appears in the status line.
  • Page 44 Operation Multi 720 4.6.4 AutoRead AR (Drift control) The AutoRead function (drift control) checks the stability of the measurement signal. The stability has a considerable ef- fect on the reproducibility of the measured values. 1 Call up the required measuring mode by pressing 2 Immerse the conductivity measuring cell into the test sample.

  • Page 45: Determining The Cell Constant

    Multi 720 Operation Determining/setting up the cell constant [C] Why determine/set Due to ageing, the cell constant slightly changes. As a re- up the cell con- sult, an inexact measured value is displayed. Calibration de- stant? termines the current value of the cell constant and stores this value in the instrument.
  • Page 46 Operation Multi 720 4 Immerse the measuring cell into the 0.010 mol/l KCL control standard. 5 Press the key to start the AR measurement to determine the cell constant. The AR flashes on the display until a stable signal is reached. The determined cell constant ist displayed.
  • Page 47 Multi 720 Operation Calibration After calibrating, the instrument automatically evaluates the evaluation current condition of the calibration. The evaluation appears on the display. Display Cell constant [cm 0.450 ... 0.500 cm 0.800 ... 1.200 cm outside of the ranges 0.450 ... 0.500 cm 0.800 ...
  • Page 48 Operation Multi 720 4.7.2 Setting up the cell constant Setting up the cell To set up the cell constant manually, proceed as follows: constant manually Note The cell constant to be set up must either be taken from the operating manual of the measuring cell or is printed on the measuring cell.
  • Page 49 Multi 720 Operation 5 To return to the measuring mode: press the key. Selecting the To select the 0.100 cm cell constant proceed as follows: 0.100 cm 1 Press the key repeatedly until LF CELL appears cell constant on the display. 2 Press the key to go to the "Determining/setting up the cell constant"...
  • Page 50 Operation Multi 720 Selecting the To select the 0.010 cm cell constant proceed as follows: 0.010 cm 1 Press the key repeatedly until LF CELL appears cell constant on the display. 2 Press the key. 3 Press the key repeatedly until the 0.0100 cm cell constant appears on the display.
  • Page 51 Multi 720 Operation Setting up the temperature compensation TC The calculation of the temperature compensation is based on the preset reference temperature, Tref 20 or Tref 25 (see section 4.9 C ONFIGURATION You can select one of the following temperature compensa- tions: Non-linear temperature compensation "nLF"...
  • Page 52 Operation Multi 720 Selecting the non- To select the non-linear temperature compensation proceed linear temperature as follows: compensation 1 Press the key repeatedly until LF tc appears on the display. 2 Press the key. 3 Press the key repeatedly until nLF appears on the display.
  • Page 53 Multi 720 Operation Selecting the linear To select the linear temperature compensation proceed as temperature com- follows: pensation 1 Press the key repeatedly until LF tc appears on the display. 2 Press the key. 3 Press the key repeatedly until the adjustable linear temperature coefficient appears on the display.
  • Page 54 Operation Multi 720 Switching off the To switch off the temp. compensation proceed as follows: temperature com- pensation 1 Press the key repeatedly until LF tc is displayed. 2 Press the key. 3 Press the key until the following display appears: 4 The temperature compensation is switched off.
  • Page 55 Multi 720 Operation Configuration You can adapt the measuring instrument to your individual requirements. To do this, the following parameters can be changed (the status on delivery is marked in bold): Temperature probe that is used pH temperature probe, for the pH measurement LF/O temperature probe...
  • Page 56 Operation Multi 720 Temperature probe 4 Set up pH TP or LF-O2 TP by pressing 5 Confirm with . P appears on the display and, if a D. O. probe is connected, the current air pressure in mbar. Air pressure 6 Confirm with .
  • Page 57 Multi 720 Operation Conductivity or resistance measurement Ω. 9 With select between S/cm and M 10 Confirm with USE appears on the display. Temperature unit 11 With select between °C and °F. 12 Confirm with . The instrument automatically changes to the previously selected measuring mode.
  • Page 58 Operation Multi 720 4.10 Reset Basic settings You can reset (initialize) the settings for the pH, oxygen and conductivity measurement separately. pH measurement The following functions for the pH measurement (pH InI) are reset to the values they had on delivery: Measuring mode Asymmetry 0 mV...
  • Page 59 Multi 720 Operation Note After a reset, the calibration data are lost. Thus, calibrate af- ter a reset. Proceed as follows to reset the settings: 1 Press and hold down the key. 2 Press the key. Resetting the pH settings 3 Toggle between no and yes by pressing yes: reset the settings for pH.
  • Page 60 Operation Multi 720 6 Confirm with . The instrument changes to the settings for the conductivity measurement. Resetting the con- ductivity settings 7 Toggle between no and yes by pressing yes: reset the settings for conductivity. no: retain settings. 8 Confirm with The instrument changes automatically to the previously selected measuring mode.
  • Page 61 Multi 720 Maintenance, cleaning, disposal Maintenance, cleaning, disposal Maintenance The measuring instrument is almost maintenance-free. The only maintenance task is replacing the batteries: 1 Open the battery compartment (1) on the underside of the instrument. 2 Remove the four batteries from the battery compartment.
  • Page 62 Maintenance, cleaning, disposal Multi 720 Cleaning Occasionally wipe the outside of the measuring instrument with a damp, lint-free cloth. Disinfect the housing with isopropanol as required. Caution The housing is made of synthetic material (ABS). Thus, avoid contact with acetone or similar detergents that contain solvents.
  • Page 63 Multi 720 What to do if... What to do if... pH system messages Cause Remedy Error message, pH electrode: – Not connected – Connect electrode – Air bubbles in front of the – Remove air bubbles diaphragm – Air in the diaphragm –...
  • Page 64 What to do if... Multi 720 Buffer solutions: – Incorrect buffer solutions – Change calibration procedure – Buffer solutions too old – Only use once. Note the shelf life – Buffer solutions depleted – Change solutions No stable Cause Remedy measured value pH electrode: –...
  • Page 65 Multi 720 What to do if... Cause Remedy Obviously incorrect measured values pH electrode: – pH electrode unsuitable – Use suitable electrode – Temperature difference – Adjust temperature of between buffer and buffers or samples sample too large – Measuring procedure not –...
  • Page 66 What to do if... Multi 720 Cause Remedy Error message, Damaged membrane – Membrane damaged – Regenerate D. O. probe – Membrane head not tight – Screw membrane head enough tight AR flashes for a Cause Remedy longer time No stable measured value –...
  • Page 67 You would like to Ursache Behebung know which soft- – e.g. question of the WTW – Press the key and ware version is in service department switch on instrument. the instrument The software version...
  • Page 68 What to do if... Multi 720...
  • Page 69 Multi 720 Technical Data Technical Data General data Storage temperature - 25 °C ... + 65 °C Ambient temperature Operating temperature 0 °C ... + 55 °C Allowable relative Annual mean: < 75 % humidity 30 days/year: 95 % Other days: 85 % Length [mm] Dimensions and...
  • Page 70 Technical Data Multi 720 FCC Class A Equipment Statement Note: This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment.
  • Page 71 Multi 720 Technical Data pH/Redox measurement - 2.00 ... + 16.00 Measuring ranges and resolution U [mV] - 199.9 ... + 199.9 - 1999 ... + 1999 T [°C] - 5.0 ... + 105.0 T [°F] + 23.0 ... + 221.0 ±...
  • Page 72 Technical Data Multi 720 Oxygen measurement Measuring ranges mg/l mbar and resolution Range I 0 ... 19.99 0 ... 199.9 0 ... 199.9 Resolution 0.01 Range II 0 ... 90.0 0 ... 600 0 ... 1250 Resolution T [°C] 0.0 ... 50.0 T [°F] +32.0 ...
  • Page 73 Multi 720 Technical Data Conductivity measurement [µS/cm] 0.000 ... 1.999 Measuring ranges (only with 0.010 cm cell constant ) and resolution 0.00 ... 19.99 (only with 0.010 cm constant and cell constant 0.100 cm 0.0 ... 199.9 0 ... 1999 [mS/cm] 0.00 ...
  • Page 74 0 °C ... 35 °C according to EN 27 888; ± 0.5 % 35 °C ... 50 °C extended nLF function according to WTW measurements Linear compensation Accuracy Test sample temperature ± 0.5 % 10 °C ... 75 °C (the accuracy percentage always refers to the measured value!) Range 0.0 ...
  • Page 75 Multi 720 Lists Lists This chapter provides additional information and orientation aids. Abbreviations The list of abbreviations explains abbreviations that appear on the display or when dealing with the instrument. Specialist terms The glossary briefly explains the meaning of the specialist terms.
  • Page 76 Calibration with DIN buffer solutions (acc. to DIN 19 266) CELL Cell constant ConCal Conventional one/two point calibration Ct... Calibration with WTW technical buffer so- lutions D. O. probe Dissolved oxygen probe Error message (see W ...) HAT TO DO IF °F...
  • Page 77 Multi 720 Lists LoBat Low Battery Batteries are almost empty Voltage unit mV/pH Unit of the electrode slope Non linear temperature compensation Overflow Display range exceeded Oxical Automatic calibration pH value Slope Salinity SELV Safety Extra Low Voltage Slope Slope setting on calibration Temperature coefficient Total dissolved solids Temperature probe...
  • Page 78 Lists Multi 720 Glossary Asymmetry Zero point of a pH electrode. AutoRange Automatic selection of the measuring range. AutoRead Monitors the electrode drift and releases the measured val- ue only after the stability criterion has been reached. In this way, this procedure ensures the highest degree of precision and reproducibility.
  • Page 79 Multi 720 Lists Drift control See A ® MultiCal Group term for the various WTW calibration procedures used for automatic calibration in buffer solutions. ® OxiCal Automatic calibration Oxygen saturation Relation of the pO in the test sample to the pO of air at the current air pressure.
  • Page 80 Lists Multi 720 Salinity The salinity is a sum parameter especially for seawater; it gives the salt content of a solution (without dimension) in ‰ Slope Specifies the voltage change per pH unit. Temperature The temperature has a very strong impact on the electrical compensation (TC) conductivity.
  • Page 81 Multi 720 Lists Index asymmetry ....102 LoBat ..... . 149 authorized use .
  • Page 82 Lists Multi 720 slope ....102 sockets ..... .89 Specific resistance .

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