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Oxygen diffusiOn meter

All it takes for 

environmental

 research

P.O. Box 4, 6987 ZG Giesbeek, 
the Netherlands

T

  +3 33 88 02 00

F

  +3 33 88 02 99

E

  [email protected]

www.eijkelkamp.com

M.4.36.E

© December 2008

OperAting instructiOns

Contents

On these operating instructions ................................................................................................................................2
Introduction   ............................................................................................................................................................2
  Description ..........................................................................................................................................................2
  . 

Oxygen diffusion rate ................................................................................................................................2

  .2 

ODR meter ................................................................................................................................................3

  .3 

Pt-electrode ...............................................................................................................................................3

    .3.  Preparation ...........................................................................................................................................3
    .3.2  Maintenance ........................................................................................................................................4
  .4 

Reference electrode ...................................................................................................................................4

    .4.  Commercial electrodes .........................................................................................................................4
    .4.2  Preparation for use ...............................................................................................................................4
    .4.3  Maintenance ........................................................................................................................................4
    .4.4  Storage ................................................................................................................................................4
    .4.5  Preparation of a used electrode ............................................................................................................5
     

.4.5.  Before (re-)generating, the electrode must be cleaned ..................................................................5

     

.4.5.2  Generating an Ag-AgCl electrode .................................................................................................5

  .5 

Brass electrode ..........................................................................................................................................5

    .5.  Maintenance ........................................................................................................................................5
2   Measurements .....................................................................................................................................................6
  2. 

Measurement of Redox ..............................................................................................................................6

  2.2 

Measurement of ODR ................................................................................................................................6

  2.3 

Checking the instrument ...........................................................................................................................7

3  Storage, transport ................................................................................................................................................8

4  Specifications

 .......................................................................................................................................................8

Literature    ............................................................................................................................................................9
Figures     ..........................................................................................................................................................0

Summary of Contents for 14.36

Page 1: ... ODR meter 3 1 3 Pt electrode 3 1 3 1 Preparation 3 1 3 2 Maintenance 4 1 4 Reference electrode 4 1 4 1 Commercial electrodes 4 1 4 2 Preparation for use 4 1 4 3 Maintenance 4 1 4 4 Storage 4 1 4 5 Preparation of a used electrode 5 1 4 5 1 Before re generating the electrode must be cleaned 5 1 4 5 2 Generating an Ag AgCl electrode 5 1 5 Brass electrode 5 1 5 1 Maintenance 5 2 Measurements 6 2 1 Me...

Page 2: ...is a very complex system The results of an ODR measurement in a soil are highly sensitive to the voltage between the Pt electrode and the soil For comparable results the conditions of measurement should be well de fined and closely controlled The ODR meter has been designed to provide a stabilised voltage of 0 65 V between the Pt electrode and the Ag AgCI reference electrode and hence of 0 428 V b...

Page 3: ...ltage At a voltage of about 0 5 volt between the Pt electrode and the soil the reduction of oxygen is the dominant process The magnitude of the cur rent will vary significantly with the voltage It is therefore important to specify the applied voltage and to keep the voltage within narrow tolerances during measurements The potential of the Pt electrode is measured with respect to an Ag AgCI referen...

Page 4: ...trical connection a female BNC connector is provided at the top of the electrode assembly The electrode vessel is mounted in a screw cap that can be screwed onto a plastic bottle with a KCI solu tion A spare cap is provided to close the bottle when the electrode is in use The reference electrode and the salt bridge are depicted in figure 3 on page 11 1 4 1 Commercial electrodes Instead of the refe...

Page 5: ...ter electrode will result in dis solvement of the Ag Doing this for a short period 30 seconds will clean the Ag electrode If necessarry the electrode can be de greased with aceton Always rinse with demi water 1 4 5 2 Generating an Ag AgCl electrode Method A After cleaning the Ag electrode is placed in a concentrated for example 5 FeCl3 solution The electrode stays in the solution for 10 minutes to...

Page 6: ...0 mV the latter reading can be taken as the equilibrium value In contrast to ODR electrodes Redox electrodes can be left longer in the soil without any noticeable change of reading After the first equilibration no further time delays are required It is important though that the part of the electrode structure that emerges from the soil is perfectly dry no rain or dew and does not move stabilise ag...

Page 7: ...ference electrode silver part head without body to middle pin connector resistance 1 ohm 5 Check Pt electrode point resistance to middle pin connector resistance 1 ohm 6 Check brass electrode to middle pin connector resistance 1ohm Check redox potential of electrodes Use a Zobell kalibration solution to check the electrodes for redox measurements The measurement value must be near the certified va...

Page 8: ... few months When the instrument has to be transported over a long distance or will be stored for a long time the reference electrode is best emptied cleaned and dried When it is to be used again the procedure as described under 1 4 2 Preparation for use should be followed 4 Specifications Range Redox 0 to 999 mV ODR With the Pt probe surface area of 2 37 10 5 m2 0 0000237 m2 0 to 999 µA correspond...

Page 9: ...mm exposed length 6 mm length 70cm Reference electrode Silver sheet 2 x 8 x 100 mm ceramic cup 100 ml PE plastic wide neck bottle probe provided with a pressure release screw Brass electrode Brass rod diameter 8 mm length 173 mm Literature An extensive discussion of the ins and outs of an ODR measurement has been given by D S McIntyre The plati num micro electrode method for soil aeration measurem...

Page 10: ...10 Figure 1 Schematic diagram ...

Page 11: ...ical data can be amended without prior notification Eijkelkamp Agrisearch Equipment is not responsible for personal damage due to improper use of the product Eijkelkamp Agrisearch Equipment is interested in your reactions and remarks about its products and operating instructions Reference electrode and salt bridge 1 BNC connector 2 Electrode head with silver electrode 3 Pressure realease screw 4 O...

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