METHODE DE NETTOYAGE DES ELECTRODES DE MATERIEL DE MESURE

A METHOD FOR CLEANING ELECTRODES IN MEASURING EQUIPMENT

Abrégé anglais

The invention relates to a method for cleaning electrodes,
especially in measuring equipments. The electrodes, when carrying
a coating, are exposed to a cleaning electric pulse having saw-tooth
wave form and an initial potential of -1,5V, which, at a
rate of 1 V/sec is reduced to 0 V and then immediately returned
to -1,5V, said cycle being repeated a number of times sufficient
to remove the coating, whereupon the electrodes are normalized
by being brought to a final 0 V potential.

Revendications

3
Claims
1. A method for cleaning electrodes, particularly in
measuring equipments, characterized in that the electrodes,
carrying a coating, are exposed to a cleaning electric pulse
having a saw-tooth wave form and an initial potential of -1,5V
which, at a rate of 1 V/sec, assumes the value of 0 V, from which
it rapidly reverts to -1,5V, said cycle being repeated a number
of times sufficient to remove the coating, whereupon the
electrodes are normalized by reduction of the potential to 0 V
as the final potential value.
2. A method according to claim 1, characterized in that the
potential is varied between its values about 20-60 times, as
determined by the type of the coating.

Description

' CA 02305980 2000-04-18
1
A method for cleaning electrodes in measuring equipment
The present invention relates to a method for cleaning
electrodes, especially in measuring equipments.
Most of the electromechanical measuring equipments or
conductivity measuring equipments today available in the
marketplace suffer from the great problem caused by deposited
coatings. Their presence result in changes of the resistance of
the electrodes and of their surface structure, which produces a
drift in the measuring instruments used. In certain specific
cases it is troublesome to clean the electrodes in voltammetric
systems for measuring residual chemicals in bleacheries. In such
environments organic substances, such as resins, are frequently
present. It is especially difficult to remove resin coatings
since they stick firmly to the electrode surface and get hard
when exposed to lowering temperatures.
The prior art methods used to keep measurement electrodes free
from inter alia resins include use of: vibrating electrodes,
moved by excenters, choke coils operating at the measurement
frequency, supersonic energy applied directly to the electrode,
mechanical scrapers, planing or brushing the electrode, vapour
or high pressure water flushing, a voltage of opposite polarity
to that of the measuring voltage applied to the electrode. The
one of those prior art methods which is most suitable for use in
voltammetric equipments is the one last mentioned.
The object of the present invention is to provide a method for
cleaning the electrodes in measuring equipments by use of a pulse
application technique eliminating the shortcomings of the prior
art methods. The features characterizing the invention are set
out in the annexed claims.
Thanks to the invention it has now become possible to provide a
method excellently satisfying its purpose and, at the same time,
being very simple and cost-effective. More specifically, the new

. ~ ' CA 02305980 2000-04-18
2
method involves use of a pulse applied repeatedly. When it is
applied there is generated a mechanical impact on the electrode
coating which is in that way efficiently removed. Consequently,
the new method does not require use of any mechanical means which
often complicates the apparatus used and makes it more expensive.
It has been established that the new method is capable of keeping
the electrodes free from coatings, also in such severe
environments as printing works and paper mills.
A preferred embodiment of the invention is described below.
In accordance with that example the method of the invention is
carried out in the following manner in connection with the
cleaning of electrodes in measuring equipments. The coatings on
the electrodes are exposed to a saw-tooth pulse having the
characteristics mentioned below. An initial potential of -1,5V
is caused to drop, at a rate of 1V/sec, to 0 V and is then, at
the maximum rate available, returned to -1,5V. This cycle is then
repeated as many times as required, typically 20-60 times, in
order completely to remove the coating.
As mentioned above, the pulse is applied repeatedly. When
reaching the electrode it triggers a mechanical impact on the
coating, hydrogen gas also being released on the electrode
surface. The process detaches the coating from the electrode
surface and the gas pushes it away therefrom. In order to
normalize the electrode,i.e. prevent polarization, the potential
reverts to 0 V at a slower rate than that used for the generation
of the pulse and the cycle is eventually concluded at zero
potential.