Frequently Asked Questions


Here are the benefits, in brief: More reliability, thanks to digital technology Longer lifetime with robust materials and proper care Process safety, knowing that the risk of measuring issues are minimized Minimal handling Easy maintenance
Absolutely. When dealing with hazardous processes or environments that can put people’s safety at risk, having a solution such as Memosens allows you to take the pH sensor to the lab for cleaning and calibration, removing the need to perform this activity in hazardous conditions.
This depends on the process, and can span anywhere from 10 seconds to 10 years. On the “short life” side of the spectrum, when measuring pH in hydrofluoric acid or solutions at 200C, the sensor will last a matter of seconds. It will still measure even in these extreme conditions, but the value will be affected by the process conditions and fast degeneration of the sensor itself. In a “common” water application, you can expect an average lifetime of 1-2 years, depending on the process conditions. The applications that allow for a longer lifetime (usually well above two years) are those involving saltwater (e.g. sea water). These are ideal for the sensor, because they do not consume the salt inside the sensor as quickly as other processes, because the salt is contained in the medium and in the sea water itself.
Сlean it frequently. The more you clean it, the longer it lasts. For most applications, cleaning the sensor every day is not efficient. Understanding and knowing your process will help you find the perfect balance that suits your process conditions. Alternatively, you can recondition your sensor by soaking it in certain solutions. In this case, you may want to use two sensors - leaving one to recover in the lab and one in the process, swapping them from time to time.
If the sensor is Memosens technology, you can simply replace it. If you have an analog sensor from another supplier, you can always replace it with an analog sensor from Endress+Hauser. If you have an analog sensor and want to upgrade to digital, you will have to replace the transmitter, too. Finally, if the sensor to be replaced is a digital sensor from a different supplier that is not supported, then you will have to replace the transmitter.
Yes. We have different configurations to fine-tune them to your needs, but in most cases you would just have to select whether you’re going to use the sensor in a “delicate” process (e.g. Food & Bev or Pharmaceutical). The sensors for these types of applications are not made of glass - so as to comply with safety standards.
You can, but be wary of the risk of higher discrepancies. If you have two different systems from different suppliers, it is ideal that they both measure the same values. This way, you can prove the measurement in two different ways. But what if they differ? You will have to either introduce a third system, or start troubleshooting and find out which one is not working properly. The other downside is introducing different manufacturers with different names or jargon, which might complicate things and cause confusion. We advise concentrating on finding the solution that works better for you and sticking with it - consider reliability, efficiency of maintenance, familiarity (a user-friendly interface), and documentation. Memosens sensors have it all. With analog systems, the differences between suppliers - especially in process readings - are greater than digital. With digital sensors, you are more likely to receive a value you can trust, thanks to better algorithms behind the measure, signal integrity, etc. In terms of savings, you are likely to lose less time and money by understanding which sensor provides the wrong readings, potentially replacing many units during this exercise. If you still opt for different suppliers, we recommend choosing systems that provide digital signal technology.
You should be able to store a pH-electrode for up to one year in your stock as long as you keep the glass membrane wet (it comes wet, and needs to be preserved that way). A better option is to store the pH-electrode in a KCl- solution. Side note: when you install a sensor you have had in stock for a long time, make sure you perform a proper calibration with two buffers.
Liquiline To Go is a complete measuring point in the palm of your hand: Transmitter, cable, and sensor. Imagine walking around your plant and measuring pH in different areas simply by dropping a sensor into the process solution directly at the point where you want to control a value, or performing the maintenance of your electrodes in the process? Furthermore, Liquiline To Go accepts other sensors in addition to pH like temperature, conductivity, ORP, etc. Swapping a sensor for the other is as easy as replacing a light bulb.

Usage and maintenance

Replacing a sensor is like replacing a light bulb: Remove the old sensor by unscrewing it and put the new one in. If you need to calibrate the sensor (this is unnecessary when using Memosens, as the sensor is already calibrated), you can either do so prior inserting it into the process, or calibrate it in the process itself.
Yes, the sensor needs to be cleaned. How often depends on your process. If you want to perform a quick check (and maintain a stable pH value in the process), go to your measuring point and read the pH value on the transmitter. Extract the sensor, clean it and reintroduce it into the process. If the reading is the same as before, your sensor should be reasonably clean. If it changed, you may need to consider cleaning your pH sensor more often.
Essentially, you can use them in all kind of processes with a temperature of less than ~140/150C. In terms of measurement, pH values are limited only by chemistry. The conditions of your process will also affect the lifetime of your sensor. That is, if you are to measure pH 0 in hydrofluoric acid, the glass around the sensor will most likely disappear in seconds. Some processes like this may face a short lifetime.
From a technical point of view, you could measure pH in temperatures as low as -20C. The prerequisite is that the medium is still in liquid form - for water applications you may need to add salt to lower the freezing point, although this may not always be a feasible option.
Not the Memosens, as they are calibrated in the factory. They also come with a certificate of calibration, which ships with the sensor itself.
There are two ways to achieve this: 1. Start with configuring one transmitter. Once you’ve finished setting it up, save the configuration on a SD Card. Insert the SD card into the rest of transmitters you would like to configure and load the configuration. 2. There is a software version of our transmitter that you can run on your Windows computer. It emulates the transmitter, so that you can configure it at your desk, then save the configuration on a SD card.
Besides the sensor, you will need a cable and a transmitter.
The temperature sensor is used to compensate for the temperature dependence of the pH-electrode itself. This is a known dependence and almost all pH-meters can do it. From a chemical point of view, the pH of a liquid at room temperature differs from that when the temperature is higher. This is due to the increasing ability of water to ionize, which in turn will indicate a drop in the pH reading. It is not easy to compensate for the temperature dependence of the solution. It is better to be aware that a solution will have different pH-values at different temperatures. You can use this temperature measurement if you wish, however the accuracy may not be enough for your process conditions (0.5-1 C degrees normally is the accuracy for a properly installed sensor in optimal conditions). In other words, do not rely on this measurement for sensitive processes.


There are 15+ languages available on the transmitter. (English (US), German, Chinese (Simplified, PR China), Czech, Dutch, French, Italian, Japanese, Polish, Portuguese, Russian, Spanish, Swedish, Turkish)
This is currently not supported out of the box. You could potentially use wireless HART, but this may bring more challenges than benefits. If you have an application that requires wireless transmitters, we would be very interested to know about it! Please get in touch.
Some transmitters accept only one sensor, and others accept up to 8. Check your transmitter’s manual for details.
The transmitter offers a basic alarm system, notifying you if the sensor breaks. Having a digital signal means that if you have a measurement value on the transmitter’s display, you know the signal bit reaches the transmitter. Be aware, though, that this reading may not represent the real value. It only confirms that if the sensor is working, then you will have a measurement.
Yes, you can. Memosens sensors can be used with Knick transmitters. This advanced technology is rapidly spreading amongst many suppliers. This allows you to have access to a great technology while not committing to a single supplier.
All the most common protocols are supported - HART, Profibus, Fieldbus, Ethernet IP, as well as the beloved 4...20mA. You can access your measurements distantly. In fact, you can even (re)configure the transmitter remotely.
This depends on the expected lifetime of the sensor (which depends on your process). However, the benefits of using a PAM solution to manage pH sensors brings only minor benefits. It may be convenient to understand when you need to order a new pH sensor, or to get a feeling for the lifetime of a sensor. Besides this, it could potentially simplify the ordering process and minimize the risk of ordering the wrong sensor.