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FAQ

What is the shelf life of your pH sensors?
All pH sensors from M4 Knick come with a minimum 2-year shelf life.
How often is calibration required with your pH sensors?
Calibration frequency depends on the application conditions (temperature, pH range, suspended solids) and the user's preferred maintenance practices. Implementing the correct sensor type for the application will also reduce calibration frequency. The Portavo portable meter produces more reliable calibration results for offline calibration of Memosens smart digital sensors.
How long will your pH sensor last in my process?
The specific application effects sensor longevity. It is important for the user to use the correct sensor for the application. In addition, Memosens smart digital technology provides sensor diagnostics to technicians. The information provides sensor conditions and suggests if sensors should be serviced or replaced.
Does M4 Knick offer a non-glass pH sensor?
Yes, M4 Knick offers pH sensors that are non-glass. An ISFET pH sensor made of FDA-compliant PEEK as well as a line of Glasteel™ sensors manufactured with a rugged enamel material.
Are your pH sensors temperature compensated?
Yes, most pH sensors from M4 Knick come with an integrated temperature detector for automatic compensation of the pH measurement. There are analog sensors in our product range that are available without integrated temperature compensation.
How do I calibrate pH sensors from M4 Knick?
You can calibrate M4 Knick pH sensors in several ways. You can utilize the traditional method of calibrating a sensor with a field mounted transmitter. You can also take advantage of the ability to calibrate offline, when using Memosens smart digital sensors, by using either our Portavo portable meters or our Memosuite sensor management software.
What makes pH sensors from M4 Knick different?
Some pH sensors from M4 Knick use a patented Silamid reference system. The most common type of reference system is a silver wire coated in AgCl. A Silamid® reference system is not an exposed Ag/AgCl wire. The tube has an internal silver coating and AgCl packed. On the end of the glass tube there is a junction which adds a second layer of protection of the reference system and allows the sensor to prolong the poisoning or interference of the reference in comparison to the standard reference wire.
What is our maximum temperature specification?
We have sensors for a wide variety of pH applications. Depending on the model, our sensors handle CIP/SIP cycles up to 284°F (140°C). Our Glasteel™ line of pH sensors are available with extended temperature specifications, please call us to discuss your application requirements.
What is our maximum pressure specification?
We have sensors for a wide variety of pH applications. Depending on the model, our sensors handle pressures up to 174 psi (12 bar). We even have some versions of our Glasteel™sensors able to handle pressures up to 1,500 psi (103 bar).
How do our sensors handle buildup?
Buildup on any pH sensor over time can impact the measurement. M4 Knick has sensors with specific junction/diaphragm and reference designs to provide stable measurements even with some buildup. We also have multiple options for integrated cleaning of the sensor within our holders and flow cells.
Can you install a pH sensor from M4 Knick upside down?
It is recommended that users mount glass pH sensors sensor at least 15°above horizontal. Some of our Glasteel™ sensors and ISFET sensor are mountable in any orientation, including upside down.
Where are ORP measurements used?
ORP measurements are often used to monitor destruction of contaminants in many processes. Common applications are chlorine control in cooling towers, aeration control in wastewater, destruction of cyanide in metals and mining, and complete removal of harmful chemicals through wet gas scrubbing.
What is ORP?
ORP or oxidation reduction potential is the measurement of the ability of a chemical substance to either oxidize or reduce another chemical substance. The measurement is made in mV (millivolts) with oxidizers having a positive (+) ORP value and reducers having a negative (-) ORP value.
Are ORP and Redox the same?
Yes, both terms are interchangeable and refer to the same measurement. ORP stands for Oxidation Reduction Potential while Redox stands for reduction/oxidation.
Does M4 Knick offer a sensor that measures both pH and ORP?
Yes, many ORP applications also have a pH measurement incorporated. M4 Knick offers two sensors which provide simultaneous pH and ORP measurements from one electrode. The SE 554 AMNS and PL-PETR provide both cost and space savings.
How do I calibrate my ORP sensor?
ORP sensors calibrating using a known standard (example: 220 mV REDOX Buffer) or validated process value. Immerse the sensor in the standard and adjusts the displayed value.
Are ORP measurements temperature compensated?
No, temperature affects ORP measurements but they are NOT corrected for it. An ORP value simply reflects the ability of whatever is in the water to oxidize whatever contaminants are in the water.
Do you have a retractable holder for any of your conductivity sensors?
The SE 615 conductivity sensor will work with all M4 Knick retractable holders.
What is a cell constant?
The ratio of the distance (d) between conductivity sensor electrodes to the area (a) of the electrodes. K = d/a K = cell constant (cm-1) a = effective area of the electrodes (cm2) d = distance between the electrodes (cm) Adjustment of the cell constant is a method for calibrating a conductivity loop to a known conductivity value.
How do you calibrate a conductivity sensor?
Conductivity sensors are calibrated using a single known value as a standard (one point calibration). An accurate process sample or known calibration standard can be used.
What is the difference between resistivity and conductivity?
Resistivity is a measure of a material's tendency to resist the flow of electrical current. Conductivity is a measure of a material's tendency to allow the flow of electrical current when a potential difference is put across it. Conductivity is the reciprocal of resistivity.
Does a conductivity measurement need to be temperature compensated?
Yes, a known temperature value is required in order to make an accurate conductivity measurement. Most conductivity sensors include temperature measurement.
Can a conductivity sensor be used for concentration measurement?
Yes, conductivity sensors can be used for measuring the concentration of many acids and bases. M4 Knick transmitters, with the exception of MemoRail, are pre-programmed with 11 concentration curves and are able to display these values.
What is inductive (toroidal) conductivity?
Inductive conductivity is sometimes called toroidal conductivity. An inductive sensor consists of two wire-wound metal toroids encased in a corrosion-resistant plastic body. One toroid is the drive coil, the other is the receive coil. The sensor is immersed in the conductive liquid. The analyzer/transmitter applies an alternating voltage to the drive coil, which induces a voltage in the liquid surrounding the coil. The voltage causes an ionic current to flow proportional to the conductance of the liquid. The ionic current induces an electronic current in the receive coil, which the analyzer/transmitter measures. The induced current is directly proportional to the conductance of the solution.
Can we measure total dissolved solids?
Yes, but only with the Portavo portable meters.
Can we measure salinity?
Yes, our transmitters/analyzers can be programmed to read % salinity in g/kg. Salinity is the concentration of dissolved salts in water.
What is the lowest conductivity value we can read?
The SE 604 and SE 605 are capable of reading conductivity values as low as 1 nS/cm.
What is our maximum temperature specification?
The SE 600 4-electrode sensor can operate up to 410ºF.
What is our maximum pressure specification?
The SE 600 4-electrode sensor and SE 605 2-electrode sensor can operate up to 362 psi.
How do we handle buildup?
Inductive (toroidal) sensors are recommended for applications with high-suspended solids and the potential for buildup.
Can M4 Knick measure oxygen in a gas phase?
Yes. Each of our oxygen sensors can measure oxygen either in an aqueous solution (dissolved) or in a gas phase up to 1,200 mbar PO2.
What is LDO?
LDO stands for Luminescent Dissolved Oxygen and is also sometimes referred to as “Optical”. LDO sensors such as the SE 740 measure oxygen concentration via interaction between the oxygen molecules in the sample and a luminescent dye layer on the sensor’s cap.
What is the lowest detection limit for M4 Knick’s oxygen sensors?
The SE 707 has a detection limit of ≥ 1 ppb (part per billion). It is designed specifically for trace measurements of oxygen.
What type of maintenance is required for M4 Knick’s oxygen sensors?
Maintenance required for your oxygen sensor depends on the model of the sensor and the application in which it's applied. Typical maintenance includes cleaning the sensor and replacing worn parts and consumables such as o-rings, membrane module and electrolyte (for amperometric sensors), or the sensor cap on a LDO sensor.
How often do you calibrate an oxygen sensor?
Calibration frequency depends on the application in which the sensor is applied. Calibration should always be done after replacement of electrolyte and/or the membrane (amperometric sensors) or replacement of the sensor cap (LDO sensors).
What are the max temperature ratings for your oxygen sensors?
We have sensors for a wide variety of oxygen applications. Depending on the model, our sensors are designed to handle temperatures up to 185°F (85°C) during continuous measurement. They are also designed to handle CIP/SIP cycles up to 284°F (140°C).
What are the max pressure ratings for your oxygen sensors?
We have sensors for a wide variety of oxygen applications. Depending on the model, our sensors are designed to handle pressures up to 174 psi (12 bar).
How do M4 Knick’s oxygen sensors handle build-up?
Build-up on any oxygen sensor over time can impact the measurement. Our sensors are designed to provide stable measurements even with some buildup on the membrane or measuring cap. We have multiple options for integrated cleaning of the sensor within our holders and flow cells.
How many sensors can our transmitters accept?
The maximum number of inputs into one of our transmitters is 3. This is only when using the Protos transmitter with Profibus or Foundation Fieldbus output. A Stratos Evo and MemoRail Modbus can accept 2 sensor inputs.
What outputs are available from our transmitters?
  • 4…20mA
  • Relay
    • Hi/Low limits
    • Alarm
    • Wash
  • Digital BUS
    • HART
    • Profibus PA/DP
    • Foundation Fieldbus
    • Modbus RTU
    • Ethernet / IP
    • Profinet
What are our power requirements?
We have both 4-wire and 2-wire loop-powered transmitters.

4-wire: 24 VDC…60 VDC, 80 VAC...230 VAC 2-wire: 14 VDC…30 VDC

What sensor diagnostics are available from our transmitters?
When using a Memosens sensor the following may be available depending upon the type of sensor and transmitter selected:
  • Sensor wear
  • Operating time
  • Lifetime calculator
  • Calibration data and evaluation
  • Glass impedance
What is MemoRail?
MemoRail is a compact, digital analyzer for measuring pH, ORP, conductivity, oxygen, and temperature with Memosens® sensors. Two analog active/passive 4 … 20 mA outputs supply the measurement values for the process parameter and temperature to the process control system or a PLC. MemoRail Modbus is a compact, digital analyzer available as a 1-channel or 2-channel version for connection and operation of digital Memosens sensors for the process variables pH, ORP, conductivity, and oxygen, as well as for use with an optical oxygen sensor. Modbus RTU can handle up to 31 devices operated in parallel. BUS address, link parameters, and data rate are selectable.
Do we have a transmitter that provides PID control?
Yes, the Protos can serve as a PID controller.
Do we offer a wireless solution?
Yes, we can provide a completely wireless measurement using solar-powered batteries and a wireless transmitter. Data is available via wireless 4...20mA or wireless HART.
What is our standard warranty for our transmitters?
We offer a 3-year warranty.
Can I upgrade transmitter software in the field?
Yes, please contact us to learn how.
Do you have a transmitter for use in electrically classified areas?
Yes, the Stratos Pro and Protos transmitters are available with FM and CSA approvals. The Stratos Evo is available with ATEX approval. MemoRail is available with a ULC hazardous rating.
What type of sensor can I connect to a Portavo portable meter?
Any Portavo portable meter designated as a “multi” meter will come with an M8 input for a Memosens cable. Portable meters designated as “multi’ can communicate with any Memosens sensor regardless of the measurement parameter. In addition, the final designation in the portable meter's model code indicates the measurement parameter for analog sensors inputs. For example, the Portavo 907 Multi pH will connect to:
  • Memosens pH, ORP, conductivity, and oxygen sensors
  • Analog pH sensors
What outputs are available with your portable meters?
The Portavo portable meters do not come with any communication outputs. You can log data using the Portavo and then export the data via a mini USB connection to a computer or laptop.
How do you power the Portavo portable meters?
You can power the Portavo portable meter with :
  • (4) AA batteries
  • Lithium-ion rechargeable battery pack
  • Plug into an outlet, computer, or tablet
Do your Portable meters come with an approval for an electrically classified area?
Yes, the Portavo 904x has FMc (U.S. and Canada) Class 1, Division 1 area classification.
What is the expected battery life for your portable meters?
Battery life depends on usage. You can order the unit with a rechargeable Lithium-Ion battery pack or you can power the unit from a wall plug.
How many data points can the portable meters log?
M4 Knick offers meters that have two different levels of data storage. The Portavo 904 can data log up to 5,000 individual data points. In the Portavo 907 and 908, you can log up to 10,000 individual data points. Datalogging time intervals are programmable.
Can you print the data stored in the portable meter directly from the meter?
A direct connection to a printer is a feature found in the Portavo 908 portable meter.
Does M4 Knick offer a carrying case for your portable meters?
Yes, M4 Knick offers a plastic carrying case with foam cutouts for the portable meter and accessories. Yes, the Protos can serve as a PID controller.
Do we offer a wireless solution?
Yes, we can provide a completely wireless measurement using solar-powered batteries and a wireless transmitter. Data is available via wireless 4...20mA or wireless HART.
What is our standard warranty for our transmitters?
We offer a 3-year warranty.
Can I upgrade transmitter software in the field?
Yes, please contact us to learn how.
Do you have a transmitter for use in electrically classified areas?
Yes, the Stratos Pro and Protos transmitters are available with FM and CSA approvals. The Stratos Evo is available with ATEX approval. MemoRail is available with a ULC hazardous rating.
Does M4 Knick offer sanitary fittings?
Yes, M4 Knick offers multiple holder options with sanitary process connections (Tri-clamp, Varivent, Ingold) and electropolished surface finishes.
Do I have the capability of automating my holder?
Yes, automated retractable holders are available in the SensoGate and Ceramat series. Options are available from simple pneumatic insertion and retraction to complete automation of the cleaning and calibration process.
What type of process connections does M4 Knick offer on their holders?
M4 Knick offers multiple process connections on our holders. NPT (male) threads, ANSI and DIN Flanges, and sanitary style connections.
Can I upgrade my manual retractable holder to a pneumatically driven one?
Yes, with SensoGate's modular design, you can exchange the drive system or upgrade it from a manual to a pneumatically driven system.
What sensor length should I use for M4 Knick retractable holders?
M4 Knick’s retractable holders utilize standard 12mm diameter x 120mm or 225mm length sensors. Our Sensogate and Ceramat holders utilize a 12 x 225mm sensor even for long insertion depth options. Our ball valve retractable holders utilize standard 12 x 120mm sensors.
What materials of construction are available with M4 Knick’s holders?
M4 Knick offers a wide variety of alloys or polymers for our holders. Common materials are Polypropylene, PVDF, Stainless Steel, Hastelloy, and Titanium.
Can I service and/or repair my retractable holder in the field?
Yes, the modular design of our retractable holders allows for easy O-ring and scraper ring replacement. Maintenance kits are also available for easy disassembly of the components in the field.
Is a ball valve the only way to isolate a sensor from the process?
No, M4 Knick’s Sensogate, Ceramat, and CSR 225 retractable holders allow for sensor isolation from the process without the use of a ball valve. The holders themselves provide isolation and incorporate safety features to protect the operator from the process. If required to meet corporate standards, the CSR 3600 is available with full port ball valve isolation.
What type of fittings do you offer?
  • Static (threaded or flange)
  • Retractable (manual or automated)
  • Immersion
  • Flow-through
  • Custom
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