CRONOS^®

If you have used a Pi controller you will know that they give you unrivalled control options but did you know that Pi’s new controllers also offer individual security for up to 20 named individuals? Pi’s controllers have always given flexibility but did you know that Pi’s new controllers can accommodate up to 16 sensors of any description?

This Focus On describes the 10 most popular innovations to be found in Pi’s new CRONOS^® and CRIUS^®.

No. 1 – Human readable service log

Both the CRONOS^® and CRIUS^® analyser/controller has a downloadable human readable service log – giving an entire history of the instrument including current settings, calibrations etc. Provides a great snapshot of how an engineer left an instrument.

No. 2 – Cloning facility

Ever had to set up many instruments with the same settings? Simply set up one and copy it to others!

No. 3 – On screen wiring diagrams

Lost the manual or can’t be bothered to find it? Pi’s analysers have the answer!

No. 4 – Want a bit more info on what’s going on with a sensor?

Pi’s new sensor maintenance pages are just for you then! Detailed information about all aspects of the signal coming off the sensor clearly available.

No. 5 – Instrument datalogs not quite giving you what you need?

Pi’s new look datalogs in CRONOS^® and CRIUS^® (downloadable) let you datalog almost everything, put graphs on the display, datalog the same parameters at more than one interval and a whole lot more. Never has instrument datalogging been so easy and complete.

No. 6 – New enclosure

The new enclosure brings a new level of flexibility being wall mountable, pole and handrail mountable and even flush mountable. Not only that, but it gives you loads of room to work in and there are even spare live, neutral and earth terminals to make wiring relays easier!

No. 7 – Not enough I/O?

Don’t worry, simply daisy chain 4 CRIUS^® together and you can use the same display, comms options etc. and increase your I/O fourfold to give up to 16 sensors.

No. 8 – Bored of reading about stuff in manuals that you don’t have?

Pi’s new manuals are bespoke to each instrument. The manual is ‘built’ to match each individual instrument so the manual only has what you have!

No. 9 – Has the operator been messing with settings they shouldn’t?

No more! With 20 individual user settable logons, you can give people access to what they need and no more.

No. 10 – Control algorithms

Pi has developed a reputation for developing great control algorithms and this has continued with the new CRONOS^® and CRIUS^® with the introduction of feed forward control algorithms and a master controller which selects the correct control philosophy to use (for use with complex systems such as coagulation control).

…nearly everything you can do in front of the analyser you can do remotely?
…we have been working closely with our customers to bring you an even better service?
…a lot of our customers have seen the number of engineer callouts drastically reduce, saving them time and money?

Pi’s sleek and modern Remote Access solution

Pi has always been a leader in developing new technology and have had a remote access system for over 10 years! The latest iteration of remote access is now a key part of our solution toolbox. Here are some of the features of our remote access:

User interface – The interface mimics the analyser, making the data and other features easy to find. Anyone already familiar with the CRIUS^® analyser will already be familiar with remote access. Anyone requiring training can now be trained remotely using remote access and Skype.

User control – Each user has their own customisable access rights for what they can view and change on the analysers. This is set by the ‘parent’ user.

Speed – The service now runs around 50 times faster than its predecessor, allowing users to connect and download the current sensor values and settings in under 30 seconds (test performed on CoagSense coagulation controller with 27 different devices such as sensors!).

Reduced data costs – By making the connection between the server and analyser more efficient, Pi has reduced the amount of data required for nearly all tasks thereby significantly reducing costs.

Customer branding – On request, Pi can brand the remote access theme to promote a customer’s brand.

Data analysis – The graphical interface is a powerful and flexible tool for viewing your sensor data. The way we handle your analyser’s data means that every single data point is stored in the cloud, allowing a user to download 3 months’ worth of data with a single click.

Password reset – If a password has been lost or forgotten, a user can enter their email address into the password reset function which will then email a list of instructions on how to reset it.

Data limit – Users can now limit how much data each analyser can use per day, meaning no more unexpected data costs.

So what can Remote Access do for you?

The remote access service has always been designed to save you time and money by allowing you access to the analyser and its data from anywhere in the world. Now remote access can assist as a tool in doing a lot more:

• Remotely checking and changing settings for customers who may not be confident in doing so or who may not have access to the analyser.
• Allowing Pi’s service team to temporarily remotely connect to the analyser if customers have an issue and are unsure about how to solve it.
• Automatically sending daily/weekly reports of data logs and/or status logs to users from the server (no mobile data costs from the analyser).
• Easily view when maintenance is required or due on analysers, allowing users to efficiently plan which sites to visit and when.
• Know when alarms activate on the unit within seconds by enabling text and/or email alerts direct from the analyser.
• Tune control values to optimise dosing without the need to visit the site.
• Analyse stored data to investigate incidents, explain issues or validate the process.
• Save money by reducing the number of callouts and the number of miles your engineers travel!

But what about security?

When the analyser and remote access server communicate, Pi uses a ‘Pre-Shared Key’. This creates a secure connection between the server and analyser. The key acts as a password and without it the analyser will not respond. The key is randomly generated in every analyser making it unique to each, and if required the key can be re-generated from the analyser. The analyser can also be connected directly to a Virtual Private Network (VPN) which blocks unwanted traffic and connections automatically and will only transfer information between the analyser and server.

How does user access work?

Each user has their own username and password. This means that what they see and what they can do can be customised so only authorised users can make changes.

How are the analysers and customers managed?

If a user creates a group, then they become that group’s ‘parent’. The ‘parent’ of a group creates the analysers and users for that group. If a user is a ‘parent’ to more than one group, they will also have the ability to create users that can access multiple groups from a single user account.

… that PID can save you money by offering better process control?
… that PID can help you maintain a setpoint, even with a variable process?
… that the days of over complex and confusing PID are over?
… that Pi can tailor a PID system to your exact requirements? You may never have to touch those settings again!

In this Focus On, Pi would like to introduce you to PID if you haven’t come across it, and discuss some of the useful advanced features of modern PID systems, like on Pi’s CRONOS^® and CRIUS^® models for those more familiar with PID.

What is PID?

PID is a mathematical tool created by engineers and is used in controllers. It is a feature often found in industrial controllers and is available in Pi’s controllers, as an inexpensive upgrade.

What is PID for?

The best way to explain what PID does, is to take an example. Most people have been to a swimming pool at some point in their lives, so this is the example we shall use. PID is also applicable in a huge variety of other processes. If you are not sure, you can always contact us to discuss your application.

When a person enters a swimming pool, they create a chlorine demand. They do this by introducing sweat, bacteria, organic molecules and other substances into the pool water. Chlorine reacts with these substances, which results in chlorine being used up and the chlorine level dropping. The chlorine level in this example, is often called the process variable or PV in the context of PID.

In order to maintain a concentration or level of chlorine, more chlorine needs to be dosed. If you dosed the same amount of chlorine per bather, the level would not be stable as all bathers create a different chlorine demand (e.g. swimming for fitness produces more sweat than swimming recreationally). Dosing manually brings in the issue of human error, and how operators approximate or calculate the amount of chlorine to dose based on current levels. Another issue with manual dosing is that it is not a continuous process, meaning it is unlikely a stable level will ever be reached.

What does PID do?

PID takes the measured level of chlorine or the PV and compares it to the desired level or set-point. This comparison gives the error which PID interprets and then calculates an output. The output is an electrical signal which controls the dosing of the appropriate chemical. The output can control heaters, dosing pumps and many other mechanisms that can be used to change the PV.

How is it used?

PID is made up of three parts, proportional, integral and derivative. Understanding what each part does helps operators choose the level of control best suited to them.

Proportional – Is the most commonly used for portion PID and suits most applications. When using proportional control, the further away the measured value is from the setpoint, the larger the output will be from the controller. This is an appropriate level of control for most processes, and users can gain a lot of control from a purely proportional system.

In some systems where the PV is lost to the process, e.g. chlorine from a pool, heat from a boiler etc., the proportional control never quite catches up with the setpoint. Users can see that although the process approaches the setpoint it rarely, if ever, gets to it. This is known as ‘droop’. The user can compensate for droop if the removal of the PV is fairly constant, simply by raising the setpoint, e.g. evaporation of chlorine from an empty pool. If droop changes often, (e.g. bather load or chlorine demand) then to eradicate the ‘droop’ then the integral part of PID can be applied to the signal to correct it.

Integral – The output from the integral term is determined by both the magnitude and the duration of the error. A small error over a long period of time will trigger a larger response than from a purely proportional system. This helps the elimination of the ‘droop’ seen in processes with continuous loss, and also serves to help reach the setpoint quicker.

Derivative – Derivative gain is rarely used and is generally set up only by expert engineers. Derivative gain uses the rate of change in the PV to try and predict future errors. This type of control is particularly susceptible to overcompensating, especially if there is even a small amount of signal noise (usually seen as spikes in the PV). Derivative gain is generally a tweak used by engineers to improve an already tight control, and is almost never used as an essential part of control.

What are the benefits of PID?

When properly set up, PID can lead to far tighter process control, which in turn can save you time and money. As an example, pool managers want to keep chlorine levels low, to improve the bathing experience and also save on chemicals. AquaSense is a chlorine analyser system that responds quickly and appropriately to a change in bather load (also known as chlorine demand). This means pool operators can save money whilst maintaining the safety of the pool. PID can also help reduce the risk of overshooting the desired setpoint, reducing the risk of dangerous overdosing of the chemicals.

Advanced Features and Safeguards

Whilst maintaining a setpoint with a PID loop is a huge advance over using threshold relays to maintain an upper and lower limit, it is sensible to control the loop with extra safeguards, such as:

• Maximum and minimum pump outputs. This is mainly used to prevent the controller from employing too aggressive a control, which can lead to overdosing. A minimum output can also be used in a system where the measured parameter is lost over time, to prevent the controller ever turning the dosing off.
• Ramp rate is a proportional control that allows users to choose how quickly or slowly the controller doses, in order to reach the setpoint. It is especially useful on startup, and can prevent the controller dosing too quickly.
• Wind up protection is an integral control, which limits the duration aspect of the control. This puts a limit on how much previous error can accumulate. Without wind up protection, there could be a very large integral value, if the process ever reaches zero or on startup.

These are all standard features in all Pi PID controllers.

Conclusion

In summary, PID is a very useful tool when used correctly, and can result in significant chemical savings, not to mention reduced pump wear and tear and lower electricity costs.