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TI01396C/07/EN/01.18
71413693
2018-02-15
Products
Solutions Services
Technical Information
Memosens CPS77D
Sterilizable and autoclavable ISFET sensor for pH
measurement
Digital with Memosens technology
Application
• Hygienic and sterile applications
• Food and pharmaceutical industry
• Biotechnology
Your benefits
• Break-resistant
– Sensor body made entirely of PEEK (FDA compliant)
– Can be installed directly in the process, saving time and cost for sampling and
laboratory analysis
• Biocompatibility successfully tested with regard to biological reactivity in vitro
(cytotoxicity) and in vivo in accordance with USP <87> and USP <88> Cl. VI
(121 °C)
• Operation at low temperatures
– Short response time
– Consistently high accuracy
• Sterilizable and autoclavable
• Longer calibration intervals than with glass electrodes
– Shorter hysteresis in event of temperature change
– Smaller measuring error following exposure to high temperatures
– Virtually no acid and alkaline errors
• Integrated temperature sensor for effective temperature compensation
• Improved alkaline stability
• Ideally suited for CIP processes when combined with an automatic retractable
assembly
• Documentation to certify compliance with requirements of pharmaceutical
industry with serial number of sensor (optional)
Advantages offered by Memosens technology
• Maximum process safety thanks to non-contact, inductive signal transmission
• Data security thanks to digital data transmission
• Very easy to use as sensor data saved in the sensor
• Predictive maintenance possible as sensor load data are recorded in the sensor
• Heartbeat
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Function and system design
U
D
U
GS
1
2
S
D
Si (n)
Si (p)
Si (p)
I
D
U
D
U
GS
1
3
4
5
6
2
D
Si (n)
Si (p)
Si (p)
I
D
S
Memosens CPS77D
Measuring principle
Ion-selective, or more generally, ion-sensitive field effect transistors (ISFET) were developed in the
1970s as an alternative to glass electrodes for pH measurement.
General principles
Ion-selective field effect transistors are based on an MOS
1)
transistor arrangement → 1, 2.
Unlike the MOS, however, the ISFET sensor does not have a metal gate (item 1) as the control
electrode. Instead, in the ISFET sensor → 2, 2 the medium (item 3) is in direct contact with
the gate insulator layer (item 2). Two highly p-conducting regions are diffused into the n-conducting
substrate material (item 5) of the semi-conductor (Si). They act as the charge-supplying electrode
("Source", S) and the charge-accepting electrode ("Drain", D). The metal gate electrode (in the case of
the MOSFET) and the medium (in the case of the ISFET) forms a capacitor with the underlying
substrate. A difference in potential (voltage) between the gate and substrate (UGS) increases the
electron density in the area between the "Source" and "Drain". A conductive channel forms
→ 2, 2(item 4), such that a current ID flows when a voltage UD is applied.
A0036074
1 MOSFET principle
1 Metal gate
2 Conductive channel (N-conducting)
2 ISFET principle
1 Reference electrode
2 Gate insulator layer
3 Medium
4 Conductive channel (N-conducting)
5 N-doped silicon substrate
6 Sensor shaft
A0003856
With the ISFET, ions that are in the medium and located in the boundary layer between the
medium/gate insulator generate the electric field (gate potential). The effect described above causes
a conductive channel to form in the silicon semi-conductor substrate between the "Source" and
"Drain", and causes current to flow between the "Source" and "Drain".
Suitable sensor circuits use the dependence of the ion-selective gate potential to generate an output
signal that is proportional to the concentration of the ion type.
pH-selective ISFET
The gate insulator acts as an ion-selective layer for H+ ions. While the gate insulator is also
impermeable to these ions (insulator effect), it allows reversible surface reactions with H+ ions.
Depending on the acidic or alkaline character of the medium, functional groups in the insulator
surface either accept or donate H+ ions (amphoteric character of the functional groups). This results
in positive charging at the insulator surface (H+ ions accepted in the acidic medium) or negative
charging at the insulator surface (H+ ions donated in the alkaline medium). Depending on the pH
value, a defined surface charge can be used to control the field effect in the channel between the
1) Metal Oxide Semiconductor
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Memosens CPS77D
"Source" and "Drain". The processes which lead to the creation of a charge potential and therefore to a
control voltage UGS between the "Gate" and "Source" are described by the Nernst equation:
Measuring system
UGS = U0 +
U
GS
U
0
R Gas constant (8.3143 J/molK) 2.3 . RT
T Temperature [K]
n Valency (1/mol)
2.3 . RT
Potential between gate and source F Faraday constant (26.803 Ah)
Offset voltage a
nF
.
lg a
ion
ion
Activity of ion type (H+)
Nernst factor
nF
At 25 °C (77 °F) the Nerst factor of the pH measurement has the value -59.16 mV/pH.
The complete measuring system comprises at least:
• ISFET sensor
• Memosens data cable: CYK10 (Memosens, digital sensor)
• Transmitter, e.g. Liquiline CM44, Liquiline CM42
• Assembly
– Immersion assembly, e.g. Dipfit CPA111
– Flow assembly, e.g. Flowfit CPA250
– Retractable assembly, e.g. Cleanfit CPA875
– Permanent installation assembly, e.g. Unifit CPA842
Additional options are available depending on the application:
Automatic cleaning and calibration system, e.g. Liquiline Control CDC90
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Food industry
1
2
3
4
5
6
7
9
10
11
8
Memosens CPS77D
A0035661
3 Complete measuring system
1 Water connection, at installation location
2 Assembly
3 Process/medium
4 Rinsing block
5 Pump canister unit
6 Pneumatic control unit
7 CDC90 control unit
8 Ethernet switch
9 Media (cleaners, buffers)
10 Compressed air line
11 Electric cable, signal cable
For detailed information on Liquiline Control CDC90: Operating Instructions BA01707C,
Technical Information TI01340C
As the ISFET sensor can be used in a broad range of applications - both with regard to temperature
and the pH value - sterilization in place (SIP) is not a problem. There is only a small range involving
high pH values in combination with high temperatures where the sensor's long-term stability is
somewhat compromised. Media with such properties reduce the insulator oxide of the ISFET chip. As
this is the pH and temperature range of CIP cleaning media, the ISFET sensor is only used here in
combination with an automatic retractable assembly.
Advantages of the CDC90 fully automated cleaning and calibration system:
• Cleaning in place (CIP):
The sensor in the retractable assembly is automatically retracted from the medium for the
duration of the alkaline phase or for the entire CIP process. The sensor is then rinsed with a
suitable cleaning agent in the rinse chamber.
• Calibration cycles can be set individually
• Reduced maintenance thanks to fully automated cleaning and calibration
• Optimum reproducibility of the measurement results
• Very low individual value tolerances thanks to automatic calibration
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Memosens CPS77D
1
2
3
4
Δ
pH
0
-0,05
-0,1
-0,15
0,05
0,1
0,15
0,2
0,25
0,3
0,35
1 M HCI
pH 1...3
1 M NaOH
ISFET CPSx7D
glass 1
glass 2
Pharmaceutical industry and biotechnology
A0036026
4 Measuring system for pharmaceutics and biotechnology
1 ISFET sensor
2 Installation assembly Unifit CPA842
3 Memosens data cable CYK10
4 Liquiline CM42 transmitter
Properties
Acid or alkaline errors
Another important advantage over the glass electrode is the lower acid or alkaline errors in extreme
pH ranges. In contrast to the glass electrode, almost no foreign ions can build up at the ISFET gate.
Between pH 1 and pH 13, the measured error averages Δ pH 0.02 (at 25 °C (77 °F)) and is therefore
at the detection limit. The following graphic shows the average measured error of the ISFET sensor
in the pH 1 to 13 range compared with two glass electrodes (2 different pH glasses) at the extreme
values of pH 0.09 (1 M HCl) and 13.86 (1 M NaOH).
5 Measured errors of the ISFET sensor compared to two different pH glass electrodes
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A0038183-EN
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Memosens CPS77D
• Resistance to breaking
The sensor's resistance to breaking is its most distinctive external feature. The entire sensor
technology is embedded in a PEEK shaft. Only the highly durable ISFET chip and the reference are
in direct contact with the medium.
• Measurement stability and sensor response time
The ISFET response times are extremely short over the entire temperature range. With the ISFET
sensor, there is no (temperature-dependent) equilibrium setting as in the gel layer of the pH glass
in a glass electrode. This means it can also be used at low temperatures without a deceleration in
the response time. The effect of large and fast temperature and pH value fluctuations on the
measured error (hysteresis) is smaller than with a glass electrode, as the stress on the pH glass
does not apply here.
Communication and data processing
Dependability Maintainability
Communication with the transmitter
Always connect digital sensors with Memosens technology to a transmitter with Memosens
technology. Data transmission to a transmitter for analog sensors is not possible.
Digital sensors can store measuring system data in the sensor. These include the following:
• Manufacturer data
– Serial number
– Order code
– Date of manufacture
• Calibration data
– Calibration date
– Calibration values
– Number of calibrations
– Serial number of the transmitter used to perform the last calibration
• Operating data
– Temperature application range
– Date of initial commissioning
– Hours of operation under extreme conditions
– Number of sterilizations
– Sensor monitoring data
Easy handling
Sensors with Memosens technology have integrated electronics that store calibration data and other
information (e. g. total hours of operation or operating hours under extreme measuring conditions).
Once the sensor has been connected, the sensor data are transferred automatically to the transmitter
and used to calculate the current measured value. As the calibration data are stored in the sensor,
the sensor can be calibrated and adjusted independently of the measuring point. The result:
• Easy calibration in the measuring lab under optimum external conditions increases the quality of
the calibration.
• Pre-calibrated sensors can be replaced quickly and easily, resulting in a dramatic increase in the
availability of the measuring point.
• Thanks to the availability of the sensor data, maintenance intervals can be accurately defined and
predictive maintenance is possible.
• The sensor history can be documented on external data carriers and in evaluation programs,.
• Thus, the current application of the sensors can be made to depend on their previous history.
Integrity
Data security thanks to digital data transmission
Memosens technology digitizes the measured values in the sensor and transmits the data to the
transmitter via a non-contact connection that is free from potential interference. The result:
• Automatic error message if sensor fails or connection between sensor and transmitter is
interrupted
• Immediate error detection increases measuring point availability
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Memosens CPS77D
GN/YE
YE
GN
BN
WH
GND
+
–
Com A
Com B
GY
Safety
Maximum process safety
With inductive transmission of the measured value using a non-contact connection, Memosens
guarantees maximum process safety and offers the following benefits:
• All problems caused by moisture are eliminated:
– Plug-in connection free from corrosion
– Measured values cannot be distorted by moisture
– Can even be connected under water
• The transmitter is galvanically decoupled from the medium. Issues concerning "symmetrical highimpedance" or "asymmetry" or an impedance converter are a thing of the past.
• EMC safety is guaranteed by screening measures for the digital transmission of measured values.
Input
Measured variable
Measuring range
Electrical connection
pH value
Temperature
0 to 14pH
–15 to 135 °C (5 to 275 °F)
Pay attention to the operating conditions in the process.
Power supply
The sensor is connected to the transmitter via the Memosens data cable CYK10.
A0024019
6 Memosens data cable CYK10
Performance characteristics
Reference operating conditions
Reference system
Reference temperature:
Reference pressure: 1013 hPa (15 psi)
The integrated reference electrode is a double-chamber reference system with a bridging electrolyte.
This has the advantage of an effective and stable contact between the junction and reference lead
and an extremely long poison diffusion path. The bridging electrolyte is highly resistant to
temperature and pressure changes.
Ag/AgCl reference lead (bridging electrolyte) with Advanced Gel 3M KCl, non-cytotoxic
Repeatability
Response time
± 0.01 pH
A closed-control loop is created each time the measuring system is switched on. The measured value
adjusts to the real value during this time.
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25 °C (77 °F)
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Memosens CPS77D
z
y
1
2
N10019
05E03
y
x
z
1
2
30 ... 45°
The settling time depends on the type and duration of the interruption:
• Supply voltage interruption, sensor remains in the medium: approx. 3-5 minutes
• Interruption of the film of liquid between the ISFET and reference: approx. 5-8 minutes
• Dry storage of the sensor for an extended period: up to 30 minutes
Response time t
Orientation
90
t < 5 s
for a buffer change from pH 4 to pH 7 and under reference operating conditions
The response of the integrated temperature sensor can be slower in the event of extreme
temperature changes. In this case, regulate the temperature of the sensor before a calibration
or measurement.
Installation
Note the direction of medium flow when installing the sensor.
Position the ISFET chip so that it is at an angle of approx. 30 to 45 ° to the flow direction (item
‣
2).
Use the rotatable terminal head for this purpose.
A0037400
7 Sensor orientation, front view
1 Serial number
2 Nameplate
8 Sensor orientation, 3D view
1 ISFET chip
2 Direction of medium flow
A0036028
When installing the sensor in an assembly, use the serial number engraved on the terminal head to
ensure correct sensor orientation. The engraving is always on the same plane as the ISFET chip and
the nameplate (z-y direction).
ISFET sensors are not designed for use in abrasive media. If these sensors are nevertheless used
in such applications, avoid direct flow to the chip. This increases the sensor operating life and
improves the sensor drift behavior. The disadvantage is that the pH value displayed is not
stable.
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Memosens CPS77D
A
B
Installation instructions
ISFET sensors can be installed in any position because there is no liquid inner lead. However, in the
event of upside-down installation an air bubble
1)
may form in the reference system and interrupt
the electrical contact between the medium and the junction.
The installed sensor should remain in dry
conditions for a maximum of 6 hours (also
applies to upside-down installation).
Make sure to follow the installation
instructions in the Operating Instructions of the
assembly used.
A0030407
9 Angle of installation
A Recommended
B Permitted, please pay careful attention to basic
conditions!
1) The sensor is free of air bubbles when delivered from the factory. Air bubbles occur, however, when
working with negative pressure, e.g. when emptying a tank.
Environment
Ambient temperature range NOTICE
Risk of damage from frost!
Do not use the sensor at temperatures below –15 °C (5 °F) .
‣
Storage temperature
Degree of protection
0 to 50 °C (32 to 122 °F)
Memosens
IP 68 (10 m (33 ft) water column, 25 °C (77 °F), 45 days, up to 135 °C (275 °F)) autoclavable
Electromagnetic compatibility (EMC)
Interference emission and interference immunity as per
• EN 61326-1:2013
• EN 61326-2-3:2013
• NAMUR NE21: 2012
Sensitivity to light
Like all semiconductor components, the ISFET chip is sensitive to light. The measured value may
fluctuate. For this reason, avoid direct sunlight during calibration and operation. Normal ambient
light does not have any significant effect on the measurement.
Process
Process temperature range t
a
–15 to 70 °C (5 to 158 °F)
t
p
–15 to 135 °C (5 to 275 °F)
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Memosens CPS77D
0
0 2 4 6 8
° C
pH
° F
80
60
40
20
100
120
32
68
104
140
176
212
248
12
14
10
A
B
C
Medium temperature depending on the pH value
At high temperatures, alkalis can irreversibly damage the gate insulator oxide over the longer term.
The sensor can only be used in the marked range (→ 10, 10) to the detriment of the sensor
operating life. If permanently exposed to 1 molar NaOH at temperatures over 65 °C (149 °F), the
sensor operating life is reduced to such an extent that permanent operation in this range is not
recommended.
Process pressure range
Conductivity
Pressure-temperature ratings
10 Area of application depending on the temperature and pH value
A Can be used without any problems
B Limited operating life
C Use not recommended
Operation at low temperatures
Sensor range of application according to the order code. Ordering information → 12
Max. 11 bar (abs.)/100 °C (160 psi (abs.)/212 °F)
0.8 bar (12 psi)(abs.) is possible as minimum.
Minimum conductivity
2)
: 50 μS/cm
Max. 11 bar (abs.)/100 °C (160 psi (abs.)/212 °F)
Sterilizable: 4 bar (abs.)/135 °C (58 psi (abs.)/275 °F), 1 h
A0037987
2) Reference conditions: Demineralized water as the measuring medium whose conductivity has been adjusted with NaOH, KCI or HCI; room
temperature; unpressurized sensor operation; change between stationary medium and flow to the sensor with 2 m/s (6.6 ft/s) fluid velocity with
lateral medium flow in the direction of the ISFET chip; the conductivity value indicated is the value determined when the measured value changes
by less than 0.2 pH in all media between stationary media and flowing media.
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Memosens CPS77D
4
100
11
° F
psi
160
212
275
135
58
1
15
° C
bar (abs.)
ISFET application range
12
(0.47)
120
(4.7)
5.7
(0.22)
50
(2)
A0036111-EN
11 Pressure-temperature rating
Design, dimensions
NOTICE
Risk of damage to electrode!
Never use the electrode outside of the listed specifications!
‣
Mechanical construction
12 Dimensions. Dimensions: mm (in)
Weight
CPS77D length 2 (120 mm (4.7 in)):
35.4 g (1.25 oz)
CPS77D length 4 (225 mm (8.7 in)): 50.3 g (1.77 oz)
CPS77D length 5 (360 mm (14.2 in)): 66 g (2.3 oz)
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A0036053
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Materials Materials in contact with the medium
Sensor shaft PEEK (FDA, 3-A)
Seals FFKM (FDA, 3-A)
Junction Ceramic, suitable for sterilization
Materials not in contact with the medium
Temperature sensor
Pt1000 (Class A according to DIN IEC 60751)
Plug-in head
CPS77D:
Memosens, rotatable
Process connections
Pg 13.5
Memosens CPS77D
Surface roughness
Ra < 0.76 µm (30 µin)
Certificates and approvals
mark
Sanitary compatibility 3-A
The product meets the requirements of the harmonized European standards. As such, it complies
with the legal specifications of the EU directives. The manufacturer confirms successful testing of the
product by affixing to it the mark.
Certified according to 3-A Standard No. 74-06
FDA compatibility
The manufacturer declares the use of FDA-listed materials.
EHEDG
Compliance with EHEDG's criteria for hygienic design
• Technical University of Munich, Research Center for Brewing and Food Quality, Freising-
• Certificate type: Type EL Class I aseptic
ASME BPE-2018
Designed in accordance with ASME criteria (American Society of Mechanical Engineers)
Weihenstephan
Regulation (EC) No. 1935/2004
Meets the requirements of Regulation (EC) No. 1935/2004
Biocompatibility
Biocompatibility successfully tested with regard to
• Biological reactivity, in vitro (cytotoxicity) according to USP <87>
• Biological reactivity, in vivo according to USP <88> Class VI, 121 °C (250 °F)
Ordering information
www.endress.com/CPS77D
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Memosens CPS77D
Accessories
Device-specific accessories Transmitter
Liquiline CM42
• Modular two-wire transmitter for hazardous and non-hazardous areas
• Hart®, PROFIBUS or FOUNDATION Fieldbus possible
• Order according to product structure
Technical Information TI00381C
Liquiline CM44
• Modular multi-channel transmitter for hazardous and non-hazardous areas
• Hart®, PROFIBUS, Modbus or EtherNet/IP possible
• Order according to product structure
Technical Information TI00444C
Cleaning and calibration system
Liquiline Control CDC90
• Fully automatic cleaning and calibration system for pH and ORP measuring points in all industries
• Cleaned, validated, calibrated and adjusted
• Product Configurator on the product page: www.endress.com/cdc90
Technical Information TI01340C
Assemblies (selection)
Dipfit CPA111
• Immersion and installation assembly made of plastic for open and closed vessels
• Product Configurator on the product page: www.endress.com/cpa111
Technical Information TI00112C
Cleanfit CPA871
• Flexible process retractable assembly for water, wastewater and the chemical industry
• For applications with standard sensors with 12 mm diameter
• Product Configurator on the product page: www.endress.com/cpa871
Technical Information TI01191C
Cleanfit CPA875
• Retractable process assembly for sterile and hygienic applications
• For in-line measurement with standard sensors with 12 mm diameter, e.g. for pH, ORP, oxygen
• Product Configurator on the product page: www.endress.com/cpa875
Technical Information TI01168C
Cleanfit CPA450
• Manual retractable assembly for installing sensors with a diameter of 120 mm in tanks and pipes
• Product Configurator on the product page: www.endress.com/cpa450
Technical Information TI00183C
Flowfit CPA250
• Flow assembly for pH/ORP measurement
• Product Configurator on the product page: www.endress.com/cpa250
Technical Information TI00041C
Unifit CPA842
• Installation assembly for food, biotechnology and pharmaceutics
• With EHEDG and 3A certificate
• Product Configurator on the product page: www.endress.com/cpa442
Technical Information TI00306C
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Memosens CPS77D
Buffer solutions
High-quality buffer solutions from Endress+Hauser - CPY20
The secondary buffer solutions have been referenced to primary reference material of the PTB
(German Federal Physico-technical Institute) or to standard reference material of NIST (National
Institute of Standards and Technology) according to DIN 19266 by a laboratory accredited by the
DAkkS (German accreditation body) according to DIN 17025.
Product Configurator on the product page: www.endress.com/cpy20
Measuring cable
Memosens data cable CYK10
• For digital sensors with Memosens technology
• Product Configurator on the product page: www.endress.com/cyk10
Technical Information TI00118C
Memosens laboratory cable CYK20
• For digital sensors with Memosens technology
• Product Configurator on the product page: www.endress.com/cyk20
Software
Memobase Plus CYZ71D
• PC software to support laboratory calibration
• Visualization and documentation of sensor management
• Sensor calibrations stored in database
• Product Configurator on the product page: www.endress.com/cyz71d
Technical Information TI00502C
Handheld instrument
Liquiline To Go CYM290, CYM291
• Portable multiparameter device for Memosens pH, conductivity and oxygen sensors
• Product Configurator on the product page: www.endress.com/cym290, www.endress.com/cym291
Technical Information TI01198C
Refer to the Operating Instructions for CYM290 or CYM291 for information on the sensors that
can be connected.
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