YOKOGAWA SC21 Series User manual
Instruction
Manual
Model SC21 series, SC29 series
pH/redox combined electrodes
2nd edition
IM12B06J02-00EN-P
Contents
1. PREFACE.......................................................................................................................3
1.1 Introduction ............................................................................................................3
1.2 Unpacking and Checking ......................................................................................3
1.3 Warranty and Service ............................................................................................3
1.4 Serial number..........................................................................................................4
2. GENERAL SPECIFICATIONS ........................................................................................5
...............................................................................5
...............................................................................6
2.3 Shipping details .....................................................................................................6
2.4 Environmental conditions......................................................................................6
2.5 Regulatory standards.............................................................................................6
3. INSTALLATION ............................................................................................................7
...............................................................................................7
3.1.1 P...................................................................................7
3.1.2. M ..................................................................................................7
...............................................................................................7
3.2.1 P...................................................................................7
3.2.2 Mounting ...................................................................................................7
4. DIMENSIONS...............................................................................................................9
5. WIRING......................................................................................................................11
6. GENERAL CALIBRATION & MAINTENANCE PROCEDURE ......................................11
................................................................................. 11
6.1.1 C..................................................................... 11
6.1.2 T.................................................................................... 11
6.1.3 C........................................................................................................ 12
...................................................................... 13
6.2.1 Functional check and calibration ......................................................... 13
6.2.2 Use and maintenance ........................................................................... 13
7. MODEL CODES...........................................................................................................14
8. SPARE PARTS .............................................................................................................15
9. CHEMICAL COMPATIBILITY .....................................................................................16
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3
1. PREFACE
1.1 Introduction
This instruction manual provides infor-
mation for the installation and use of the
Yokogawa combined pH electrodes SC21
The SC21 series is already Yokogawa’s
trusted range of combination pH elec-
trodes for many years.
uses a ceramic reference junction with
through the junction, while small,
remains the safest way to prevent
clogging and to protect the internal ref-
processes with a constant pH value or
for processes where the Redox poten-
tial depends on the pH to achieve a
pH-compensated Redox potential.
Features
• Wide range of electrodes to suit
almost all process conditions.
• Color code strips for easy
connection cables.
• High degree of standardization for
• Separate electrode system for high
accuracy applications.
1.2 Unpacking and Checking
Upon delivery, unpack the sensor care-
fully and inspect it to ensure it was not
damaged during shipment. If damage
is found, retain the original packing
materials and then immediately notify
the carrier and the relevant Yokogawa
Serial Number on the sensor are the
same as on the packing list. Also, check
and correct.
1.3 Warranty and Service
Yokogawa products and parts are guar-
anteed free from defects in workman-
ship and material under normal use
months from the date of shipment from
the manufacturer. Individual sales or-
ganizations can deviate from the typical
warranty period, and the conditions of
sale relating to the original purchase
order should be consulted. Damage
caused by wear and tear, inadequate
of chemical processes are excluded from
this warranty coverage. In the event of
a warranty claim, the defective goods
Service Department of the relevant sales
Organization for repair or replacement
The following information must be
included in the letter accompanying the
returned goods:
• Model Code and Serial Number.
• Original Purchase Order and Date.
• Length of time in service and descrip-
tion of the process.
• Description of the fault and circum-
stances of the failure.
• Process/environmental conditions
that may be related to the failure of the
sensor
• Statement as to whether warranty or
non-warranty service is requested.
• Complete shipping and billing instruc-
tions for the return of material, plus the
name and phone number of a contact
person that can be reached for further
information.
• Clean Statement
Returned goods that have been in
decontaminated and disinfected prior
to shipment. Goods should carry a cer-
safety of our employees. Material Safety
Data sheets must be included for all
components of the process to which the
1.4 Serial number
X1X2 Production location
X3X4Year/Month code
X5X6X7X8X Tracking number
Example: N3P600028
Table 1: Production Year code Table 2: Production Month code
4
IM12B06J02-00EN-P
Year Year
code Year Year
code Month Month code
2014 P 2027 4 January 1
2015 R 2028 5 February 2
2016 S 6 March 3
2017 T 2030 7 April 4
2018 U 2031 8 May 5
V 2032 June 6
2020 W 2033 A July 7
2021 X 2034 B August 8
2022 Y 2035 C September
2023 Z 2036 D October A
2024 1 2037 E November B
2025 2 2038 F December C
2026 3 G
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2. GENERAL SPECIFICATIONS
Sensor type : pH glass electrode
Membrane : G or L glass
Glass shape
- AAP26 : Bulb
- AGP24 : Bulb
- AGP26 : Dome
- ALP26 : Dome
- AGP64 : Bulb
- AGC55 : Heavy duty dome
- AGC11 : Bulb
Glass impedance range @25°C
Reference type
- AGC55 : Flow
Reference system : Ag/AgCl
Reference liquid
- AAP26 : Saturated KCl
- AGP24 : 3,3 M KCl
- AGP26 : Saturated KCl
- ALP26 : Saturated KCl
- AGP64 : 3,3 M KCl
- AGC55 : 3,3 M KCl
- AGC11 : 3,3 M KCl
Junction type : Single junction
Wetted parts construction materials
O-rings : FKM
Stabilisation time 0.02 pH/10sec: <30 sec
Operating range
pH
- AAP26 : 0 to 14
- AGP24 : 0 to 14
- AGP26 : 0 to 14
- ALP26 : 0 to 14
- AGP64 : 0 to 14
- AGC55 : 0 to 14
- AGC11 : 0 to 14
Flow rate
- AAP26 : N/A
- AGP24 : N/A
- AGP26 : N/A
- ALP26 : N/A
- AGP64 : N/A
- AGC55 : Max. 3 ml/day@10kPa
- AGC11 : N/A
Temperature
- AAP26 : 0°C ... 110°C
- AGP24 : 0°C ... 80°C
- AGP26 : 0°C ... 110°C
- ALP26 : 20°C ... 130°C
- AGP64 : 0°C ... 80°C
- AGC55 : 0°C ... 110°C*
- AGC11 : 0°C ... 85°C
*only when atm>vapor pressure to prevent boil-
ing, otherwise 0°C ... 100°C
Pressure
- AAP26 : 1,5 kPa …500 kPa
- AGP24 : 1,5 kPa …500 kPa
- AGP26 : 1,5 kPa …500 kPa
- ALP26 : 1,5 kPa …500 kPa
- AGP64 : 1,5 kPa …500 kPa
- AGC55 : 1,5 kPa …500 kPa*
- AGC11 : Atmospheric
* Only with pressure reservoir
Conductivity : > 50 µS/cm
2.3 Shipping details
10.2x1x1 inch
SC21C-AGC55, SC29C-PTC55
11.8x3.7x2.8 inch
2.4 Environmental conditions
Storage temperature: -10 to +50 ºC
When an electrode remains unused for
electrode completely with electrolyte
the protective cover around the mem-
6
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2.5 Regulatory standards
CE
- RoHS Directive 2011/65/EU
2015/863 amending Annex II as regards
the list of restricted substances, and
by applying Annex IV as regards the
application of sensors, detectors and
electrodes, by applying the following
standards:
EN-IEC 63000: 2018
Technical documentation for the
assessment of electrical and electronic
products with respect to the restriction
of hazardous substances.
UKCA
- RoHS
The Restriction of the Use of Certain
Hazardous Substances in Electrical and
Electronic Equipment Regulations 2012
Combined Redox/reference, electrode
Measuring range : -1500...1500mV
Temp range : -10 to 100 °C
Pressure range : 1,5 kPa ... 500 kPa
Membrane : Solid Platinum cup
Diaphragm : Porous PTFE
Reference system : Ag/AgCl Sat’d. KCl
Type SC29C-PTC55
Combined Redox/reference electrode
Temp range : -10 to 100 °C
Pressure range : 1,5 kPa ... 500 kPa
Membrane : Solid Platinum cup
Diaphragm : Ceramic
Reference system : Ag/AgCl 3.3m. KCl
Type SC29-PTG29
Combined Redox/glass electrode
Temp range : 0 to 100 °C
Pressure range : 1,5 kPa ... 1000 kPa
Membrane : Solid Platinum cup
Glass : general purpose pH
glass
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3. INSTALLATION
3.1.1 P
For accurate pH measurement, a gel
layer must be formed on the mem-
brane surface. For this reason, the
pH-sensitive part of the electrode
should be soaked for 24 hours before
the electrode is used.
When an electrode has been stored
dry, and you need to use it immediately
do so, but as a result, initial regular
calibration will be required until the gel
layer is formed.
The electrode, when dispatched by
Yokogawa, has a protective cover cap
-
brane which ensures you can use the
electrode immediately. Flow electrodes
opening, which is sealed with a cap or
stopper.
NOTE:
Before installation, the above men-
tioned stopper and protective cover
cap must be removed. If required, the
AGC55 may be connected to a reservoir
of electrolyte solution. To maintain a
-
tems, the reservoir must be placed so
that the level of the electrolyte is above
the level of the measuring liquid. Only
under these circumstances will the
correct electrical contact between the
reference system and the measuring
liquid be guaranteed.
3.1.2. M
The combined electrodes must be
connected with a Coax cable type
WU20-PC, marked with a blue strip. In
areas where electrical interference is
likely, we recommend using the Triax
electrode cable type WU20-LT.. marked
with a blue strip. The cables meet the
requirement of IP65 and can be used
shown in Fig. 1.
The Yokogawa nut can be ordered under
part number: K1500DW.
RESERVOIR FOR SC21C-AGC55
The reservoir, including the connection
kit and tubing, can be ordered sepa-
rately. The connection of the tubing to
the sensor is described in Fig. 5. At the
reservoir side, Yokogawa provides a so
called swagelock connection.
NOTE: Avoid air bubbles in the tubing.
3.2.1 P
After removing the dust cap from the
connector and the protective cover from
the measuring part, the electrode is
ready for use.
NOTE:
For accurate measurements with a Re-
dox/glass electrode, a gel layer must be
formed on the glass membrane surface.
For this reason, the membrane should
be soaked for 24 hours before the
electrode is used. When an electrode has
been stored dry, and you need to use it
-
-
quent re-calibration will be required until
the gel layer is formed. The electrode,
when despatched, has a protective cover
glass membrane which ensures you can
use the electrode immediately.
3.2.2 Mounting
The mounting of the combined Redox/
carried out, as shown in the following
into a PG13.5 process connection. The
3 - 4 on the next page.
Fig. 1. Yokogawa connec-
8
IM12B06J02-00EN-P
Fig. 2. Standard mounting with mounting
set FP20-R12, FP20-S12
Fig. 4. Mounting the tube connection for the SC21C-AGC55
PG 13.5
K1520JN
4. DIMENSIONS Units in mm
Fig. 7. SC21-AGP26
SC21-ALP26
Fig. 6. SC21-AGP24
Fig. 5. SC21-AAP26
Fig. 8.SC21-AGC11
Fig. 11. SC21C-AGC55
Fig. 10. SC21C-AGP64
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5. WIRING
Wiring combined pH/redox electrodes
depending on electrode type is done
using WU20 coax or triax cables. For
cable color coding, refer to IM 12B6W1-
01E-H. Depending on the chosen host,
refer to the respective IM.
6. GENERAL CALIBRATION &
MAINTENANCE PROCEDURE
The isothermal point of intersection of
-
solution in the electrode or the reservoir.
-
able as spare part nr: K1520VA.
The electrodes of the type SC21-...2. are
this type of electrode has probably been
used at a temperature too high for this
electrode. Therefore, replacement with
-
mended.
6.1.1 C
solutions with known pH values are
required. It is recommended that one
The following is a very general 2-point
calibration procedure.
1. Refer to the appropriate Instrument
Instruction Manual for Calibration
2.
3. Rinse the sensor thoroughly with
4. -
5. Rinse the sensor thoroughly with
6. Immerse the sensor in the second
7. Repeat Step 4.
During calibration, the temperature
compensation should be active. After
the calibration is complete, replace or
re-install the sensor into the process.
NOTE:
and the temperature compensation
must be connected. The temperature of
indicated on the type plate.
6.1.2 T
Generally, faults are caused by:
a. Sensitivity decrease of the mem-
brane. When this occurs, the electrode
must be cleaned with a suitable deter-
gent.
1. Depositions of hydroxides lime,
iron, and hydroxide can be removed
by immersing the electrode in a
diluted solution of hydrochloric acid
and then rinsing it with water.
2. Depositions of oil and fat can be
removed by means of hot water
in conjunction with a domestic
washing solution. When the result is
unsatisfactory, a domestic abrasive
may be carefully used.
3. Albuminous depositions can be
removed by means of a solvent
containing: 8,5 ml concentrated
hydrochloric acid, 10 g pepsin, and
1 liter demi-water.
NOTE: When polar solvents are used for
special cleaning purposes, it is necessary
to soak the electrode for some time after
the gel layer.
is necessary.
IM12B06J02-00EN-P
12
b. Leakage to earth.
Fault indications can be expected when
the resistance between the reference
-
trode cable is in good condition. Second,
check if the connector contacts and the
terminals in the measuring instrument or
connection box are clean and dry.
c. Short circuit by break or leakage.
The pH meter reading remains approxi-
mately pH 7 and is not dependent on the
pH value of the liquid being measured.
If this occurs, the electrode should be
replaced.
d. Diaphragm poisoning
Strongly polluted liquids can cause the
diaphragm to foul very quickly. As a result,
there will be a transition resistance over
the diaphragm. When this resistance
an incorrect indication of the measured
value will occur. The above fault frequently
e.g., with adverse pressure variations due
to the medium, pumps, or too low electro-
lyte level.
Fouled electrodes can be cleaned with
hot water in conjunction with a domestic
washing solution if necessary. When the
fouling is caused by fat or hydroxides
diluted acid respectively is recommended.
The ceramic diaphragm of electrode types
SC21C-AGC.. can be cleaned by lightly
SC21-...2. to place the electrode for a
period in an electrolyte solution at 80°C
and let them remain until the solution has
completely cooled.
e. Poisoning.
An electrode can be poisoned by the
penetration of the process liquid, or by
medium through the diaphragm. In
addition, the inner liquid in combination
with dissolved particles from the process
medium, may give deposits that block the
When poisoning occurs, replacement of
the electrode will normally be necessary.
occurs, it is recommended to use an
alternative type of electrode.
f. Poor conduction of the process liquid.
When the electrical conduction of the
process liquid is very low, an unstability
of reading will occur. This problem may
be cured either by adding electrolyte
solution to the process liquid or, if this
is not possible, by making the reference
input of the measuring instrument high
impedance.
g. Degrading of the glass membrane.
Degrading has one or more of the fol-
– decrease in speed of response
– increase of the electrical resistance
– decrease of sensitivity
– zero point shift
makes it necessary to carry out re-cali-
bration of the electrode system reg-
ularly. The frequency depends on the
required accuracy, the composition of
the sample to be measured, and the
temperature; e.g., if the lifetime of an
120°C. It is possible to re-activate an
aged electrode by immersing it for 10
seconds in a P.V.C. beaker containing a
-
the electrode must be cleaned carefully.
WARNING:
As a result of the strong etching proper-
ties of the acid, the handling should be
done carefully and in consultation with a
6.1.3 C
A quick check for the correct functioning
of a combined electrode can be made as
follows. First, connect the reference lead
of this electrode to the reference input
of a pH meter. A known good reference
electrode with the same reference
system should be connected to the
glass electrode input of the meter. After
IM12B06J02-00EN-P
13
solution. The meter reading should be
-
-
ence part of the electrode is functioning
correctly.
A quick check of the correct functioning
of the pH part of the combined electrode
can be made by connecting the pH-sen-
sitive part to the glass electrode input of
a pH meter and a known good reference
electrode to the reference lead of this
meter. If the calibration procedure de-
scribed in 3.2 gives a correct adjustment,
the pH-sensitive part of the combined
electrode functions correctly.
6.2.1 Functional check and calibration
A check for a correct functioning of a
combined electrode can easily be made
4.01 pH with quinhydrone.
-
mV and 265 mV, respectively. Mostly
only 1-point calibrations are performed.
Some analyzers also have the possibility
6.2.2 Use and maintenance
- Cleaning
The electrode should be cleaned with
care using a soft cloth or tissue soaked
in soap suds, alcohol, acetone, or white
spirit. If the deposit is persistent, it may
be removed using a domestic washing
liquid diluted with water. This method
electrode, and consequently, precaution
is required.
- Insulation
It is essential that a high insulation
resistance is maintained between the
electrode and its screen. This means that
the correct electrode cable is used, and
the connector is kept dry and clean at
all times. If a connector box is used, this
must be an approved type and main-
tained in a clean and dry condition.
- Storage
When an electrode is to remain unused
for a long period, it is necessary to store
it as follows:
AGC55
Fill the electrode completely with electro-
in the wet pocket.
AGP26,
ALP26,
AGP24,
store the electrode in the wet pocket.
7. MODEL CODES
Table 3: pH combination electrodes model codes
Model Sux Code Option code Description
SC21 Combined pH
-AAP26 Comb. pH, non ow
-AGP24 Comb. pH, non ow
-AGP26 Comb. pH, non ow, heavy duty
-ALP26 Comb. pH, non ow, heavy duty
-AGC11 Comb. pH, DIN size
Model Sux Code Option code Description
SC21C Combined pH with compact connector
-AGP26 Comb. pH, non ow, heavy duty
-AGP64 Comb. pH, non ow
-AGC55 Comb. pH, ow, heavy duty
Model Sux Code Option code Description
SC29 Combined pH/redox
- PTG29 Comb. pH/redox, Pt
- PTP29 Comb. redox Pt, ref, non ow
Model Sux Code Option code Description
SC29C Combined pH/redox
- PTC55 Comb. redox Pt, ref, rell
- PTP29 Comb. redox Pt, ref, non ow
IM12B06J02-00EN-P
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8. SPARE PARTS
Table 4: pH combination electrodes model codes
Part
Number Description
Sensor spare part selection
SC21 SC21C SC29 SC29C
K1500BZ X X X X
K1500FU KCl reservoir PVC for F*20 X
K1500GA 5 m tube for KCl reservoir X X X
K1500GF 1 Molal KCl sol. 250 ml X X X X
K1500GG 1 Molal KCl sol. 250 ml, thickened X X X X
K1520FJ Tubing set, chem. cleaning 5m X X X
K1520FK Tubing set, chem. cleaning 10m X X X
K1520VA 3.3 Molal KCL solution X X X
K1520VN 3.3 molal KCl sol. 250 ml. thickened X X X
K1520YA /KR for PD/PF/PS20 holders X X X
K1500DV X X
K1520JL Adapter Y-Cap - PG13.5 SS X X
K1520JN Adapter M25x1.5 - PG13.5 PVC X X
K1520JP Adapter M25x1.5 - PG13.5 SS X X
K1523JA Adapter PG13.5 in F*40 PPO X X
K1523JB Adapter PG13.5 to ¾”NPT PPO X X
K1523JC Adapter PG13.5-sensors in F*40 SS X X
K1523JD Adapter PG13.5 to ¾” NPT SS X X
IM12B06J02-00EN-P
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Subject to change without notice
Copyright©
Printed in The Netherlands, 02-2307
IM12B06J02-00EN-P
9. CHEMICAL COMPATIBILITY
Table 5: 2
Note2:Information in this list is based on our general experience and literature data and given in good faith.
However, Yokogawa is unable to accept responsibility for claims related to this information.
This manual suits for next models
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