SenTix® ORP 900
ORP electrode
ba75845e01 08/2009
Operating manual
SenTix
Note
The latest version of the present operating manual can be found on the
Internet under www.WTW.com.
12
Copyright © Weilheim 2009, WTW GmbH
Reprinting - even as excerpts - is only allowed with the explicit written
authorization of WTW GmbH, Weilheim.
Printed in Germany.
ba75845e01 08/2009
SenTix General information
General information
Automatic sensor
recognition
The sensor electronics with the stored sensor data is in the connecting head
of the electrode. The data include, among other things, the sensor type and
series number. The data is recalled by the meter when the sensor is
connected and is used for measurement and for measured value documentation.
The digital transmission technique guarantees the failure-free communication with the meter even with long connection cables. If the sensor firmware
is enhanced by WTW, it can be updated via the meter.
Technical data
General data Reference electrolyte 3 mol/l KCl, Ag+free
Junction Ceramic
Measurement and
application
characteristics
Electrode material and
shape
mV measuring range - 1250.0 ... + 1250.0
Allowed temperature range 0 ... 100 °C (32 ... 212 ° F)
Typical application Laboratory
Platinum / circle
Shaft dimensions,
material, electrical
connection
Connection cable Length 1.5 m
Accuracy of the
IDS measuring
technique
Shaft length 120 mm
Shaft diameter 12 mm
Shaft material Glass
Combination electrode con-
nection
Meter connection Digital plug
Diameter 4.3 mm
Smallest allowed
bend radius
Plug type Socket, 4 pins
Measured parameter Accuracy (± 1 digit)
U [mV] ± 0.2
Fixed cable
Fixed installation: 20 mm
Flexible use: 60 mm
ba75845e01 08/2009
13
Commissioning, measuring, checking SenTix
Refilling
opening
Commissioning, measuring, checking
Note
For ORP electrodes with platinum electrode, please follow the instructions in
Abschnitt A
Commissioning Prepare the electrode for measuring as follows:
z Open the refilling opening for the reference electrolyte solution. Depend-
ing on the model, the stopper of the refilling opening is an elastomer stopper or a slider.
The refilling opening must always be open during measurement!
CTIVATING PLATINUM ELECTRODES.
General rules for
measuring
z Remove the watering cap from the electrode tip. Possible salt deposits in
the area of the watering cap do not affect the measuring characteristics
and can easily be removed with deionized water.
Note
Please keep the watering cap. It is required for the electrode to be stored.
Always keep the watering cap clean.
z Connect the combination electrode to the meter.
z Measure with the electrode according to the operating manual of the meter
and observe the following rules while doing so:
z Make sure the refilling opening for the reference electrolyte solution is
open.
z Avoid the carryover of sample solution from one measurement to the next
as follows:
– Shortly rinse the sample beakers with the solution the beakers are to
be filled with next.
– Between measurements, rinse the electrode with the solution that fol-
lows. Alternatively, you can also rinse the electrode with deionized water and then carefully dab it dry.
z Immerse the electrode in the solution in a vertical or slightly tilted position.
14
z Make sure the immersion depth is correct. The junction must be complete-
ly submersed in the solution. The junction is in the area of the bottom end
of the shaft (see arrow).
ba75845e01 08/2009
SenTix Commissioning, measuring, checking
Conversion to
normal hydrogen
electrode
T (°C) T (°F) U
0 32 +224 35 95 +200
SenTix
®
ORP 900
At the same time, the level of the reference electrolyte must be at least 2
cm above the level of the solution.
U
= U
H
with: U
Meas
H
U
Meas
U
Ref
+ U
Ref
= ORP, referring to the normal hydrogen electrode
= Measured ORP
= Voltage of the reference system compared to the normal
hydrogen electrode
U
is temperature dependent and can be taken from the following table (see
Ref
also DIN 38404-6):
SenTix
[mV] T (°C) T (°F) U
Ref
®
ORP 900 SenTix® ORP 900
Ref
[mV]
5 41 +221 40 104 +196
10 50 +217 45 113 +192
15 59 +214 50 122 +188
20 68 +211 55 131 +184
25 77 +207 60 140 +180
30 86 +203
ba75845e01 08/2009
15
Aging SenTix
Storage
During short
measuring breaks
Overnight or
longer
Immerse the electrode in the reference electrolyte with the refilling opening
open.
Electrode Reference electrolyte WTW model
(see page 19)
SenTix
Prior to the next measurement, shortly rinse the electrode with the test
sample or deionized water.
Insert the clean electrode into the watering cap filled with reference
electrolyte and shut the refilling opening.
Note
During longer storing periods, salt sediments may develop on the watering
cap. They do not affect the measuring characteristics and can easily be removed with deionized water when the electrode is put into operation again.
®
ORP 900 3 mol/l KCl, Ag+free KCl-250 (250 ml)
Aging
Every ORP electrode undergoes a natural aging process. Extreme operating
conditions can considerably shorten the lifetime of the electrode. These are:
z Strong acids or lyes, hydrofluoric acid, organic solvents, oils, fats, bro-
mides, sulfides, iodides, proteins
z High temperatures
z High changes in pH and temperature.
The warranty does not cover failure caused by measuring conditions and
mechanical damage.
16
ba75845e01 08/2009
SenTix Aging
KCl-250
Maintenance and cleaning
During operation, a small amount of reference electrolyte leaks through the
junction from the electrode into the test sample. If the level of reference
electrolyte becomes too low with time, refill it through the refilling opening.
Refilling the
reference
electrolyte
Refilling is very easy using a dropping bottle. Proceed as follows:
z Cut off the tip of the dropping bottle at a right angle until the opening in the
tip can be seen
z Open the refilling opening of the electrode
z Press the tip of the dropping bottle into the refilling opening while turning
it slightly
z Pump several small quantities of the reference electrolyte into the stem
using the dropper bottle
z Pull the dropping bottle out of the refilling opening while turning it slightly
as necessary.
ba75845e01 08/2009
17
Activating platinum electrodes SenTix
Cleaning Remove water-soluble contamination by rinsing with deionized water. Re-
move other contamination as follows:
Contamination Cleaning procedure
Fat and oil Rinse with water containing household wash-
ing-up liquid
Lime and hydroxide deposits Rinse with citric acid (10 % by weight)
Protein Immerse in pepsin cleaning solution PEP/pH
for approx. 1 hour.
Note:
Make sure the level of the reference
electrolyte is above that of the cleaning solution.
After cleaning Rinse the electrode with deionized water.
First-time
activation during
installation and as
required
Activation during
very long set-up
times
Activating platinum electrodes
For first-time activation use the activation powder from the SORT/RH reagent
set (component of the SORT/RH reagent set). Immerse the moist (but not
dripping) platinum electrode into the activation powder and rotate the
electrode several times in the powder. Then remove the activation powder
under flowing water with a soft brush (e.g. toothbrush).
When changing from oxidizing to reducing test solutions and vice versa this
can result in set-up times that can take significantly more than an hour. In this
case pretreatment (activation) of the platinum surface can shorten the set-up
time. The type of pretreatment (reducing or oxidizing) is based on the pH value and the ORP voltage (U
timated for the first measurement.
The type of pretreatment can then be determined using the following diagram
where U
is based on the normal hydrogen electrode:
H
) of the test solution where the latter must be es-
H
18
ba75845e01 08/2009
SenTix Wear parts and accessories
1000
800
600
400
200
20481012146
0
pH value
U
H
in mV
oxidizing pretreatment
reducing pretreatment
Oxidizing pretreatment
Immerse the platinum electrode for two to three
days in a sulfuric acid chlorine solution. Chlorine
powder for producing the solution is included in the
SORT/RH reagent set.
Note:
The diaphragm must not be immersed in the
chlorine solution!
Reducing pretreatment
When the electrode is ready for the test immerse it
in the RH 28 ORP buffer solution and wait for a stable measured value.
Note
Detailed information on activating platinum electrodes, such as how to produce the chlorine solution, is given in the WTW application report entitled R
GENERATING ORP ELECTRODES. The application report is included in the
SORT/RH reagent set.
Wear parts and accessories
Description Model Order no.
Reference electrolyte solution 3 mol/l KCl,
+
Ag
free (250 ml)
Reagent set for regenerating ORP platinum
electrodes
,consisting of 10 g activation powder and 30 g
chlorine powder
ORP buffer solution for checking ORP electrodes
= 427 mV, bottle of 250 ml
U
H
Pepsin cleaning solution,
3 bottles of 250 ml each
KCl-250 109 705
SORT/RH 109 730
RH 28 109 740
PEP/pH 109 648
E-
ba75845e01 08/2009
19
Wear parts and accessories SenTix
20
ba75845e01 08/2009
Loading...