Recommended Housings; Theory Of The Polarographic Sensor; Introduction - Mettler Toledo InPro 6850i Bedienungsanleitung

32
Parameter Fit Guide for Transmitter M400
Conventional Sensors
pH/ORP
Cond 2-electrode
Cond 4-electrode
DO ppm
DO ppb
ISM sensors
pH/ORP
Cond 2-electrode*
Cond 4-electrode*
DO ppm
DO ppm optical**
DO ppb
DO traces**
* Available as of Q4/2008
** Available as of Q3/2008
Transmitters M420
M420 O
M420 O
M420 O
M420 O
9.5

Recommended housings

Housing (12 mm
Static housing
InFit 761 CIP
Retractable housings
InTrac 777e
InTrac 797e
Immersion housing
InDip 550
Note: The housings are available in different versions.
Please contact your local METTLER TOLEDO sales or-
ganization to get the right ordering information.
10

Theory of the polarographic sensor

10.1 Introduction

Two types of electrodes are employed in analytical
work: potentiometric and amperometric electrodes.
– Potentiometric electrodes develop a voltage gener-
ated by the activity of a particular ion. Examples of
such electrodes are glass electrodes (like pH elec-
trodes) and most ion-selective electrodes. Their
individual potentials cannot be determined. The
measurable quantity is the difference of potential
between the measuring electrode and an inert
reference electrode. The potential of the reference
electrode must be constant.
All potentiometric electrodes are subject to Nernst's
law and for this reason electrodes and measuring
instruments are in most cases interchangeable. An
important requirement of potentiometric measure-
ments is the virtually currentless determination of
InPro 6850i, 6900i, 6950i
52 206 349
InPro 6850i / 6900i / 6950i O
H
2
H OUT2
2
XH
2
XH OUT2
2
)
2
M400 M400
Type 1 Type 2
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© 02 / 09 Mettler-Toledo AG
Printed in Switzerland
Sensor 12 / 25 mm
M400
Type 3
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Order No.
52 121 415
52 121 416
52 121 417
52 121 418
Order No.
Please ask
your local
METTLER TOLEDO
representative.