Multi-Parameter Analyser – CRONOS® and CRIUS®

You probably know that Process Instruments offers a cloud based remote access service for our CRIUS^®4.0 analyser, but did you know that…

…nearly everything you can do in front of the analyser you can do remotely?

…the CRIUS^®4.0 is the first analyser in the world to utilise MQTT, allowing for real time data without a delay?

…customers have seen the number of engineer callouts drastically reduce, saving them time and money?

…Control InSite has been allowing engineers to access CRIUS^®4.0 remotely, keeping them safe during COVID?

Pi’s sleek and modern remote access solution Control InSite now utilises MQTT (an Internet of Things communications protocol)

Pi has always been a leader in developing new technology and have had a remote access system for over 15 years! The latest iteration of remote access, is called Control InSite and is now a key part of our solution toolbox. Here are some of the features of our remote access:

User interface – A modern and intuitive user interface makes using Control InSite simple. Anyone requiring training can now be trained remotely using remote access and Teams or Zoom.

Speed – The service now runs around 50 times faster than its predecessors, allowing users to connect and download the current sensor values and settings in under 30 seconds (test performed on a 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.

SIM card – By utilising IoT protocols, CRIUS^®4.0 remote access can use any data enabled SIM card.

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.

Email and text alarms – Direct from the server, cheap and reliable to up to 5 SMS recipients and 5 email recipients.

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

So what can Control InSite 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.
• 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 optimize 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?

MQTT is an encrypted ‘internet of things’ communications protocol designed to provide excellent security, so no worries there.

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.

Conclusion

Using MQTT means that communication with the CRIUS^®4.0 is quick, inexpensive, reliable and secure. The frequency of communication that MQTT allows means that the data you are looking at is effectively live. The size of the packets means that there is no increased data overhead so the costs are effectively the same or lower than other communications protocols that can’t provide live data.

The way the communications works is that the CRIUS^®4.0 is in communication to a cloud based ‘broker’. It is then possible for other cloud based services to ‘subscribe’ to the data of that CRIUS^®4.0. This means that at the same time the CRIUS^®4.0 is talking to Control InSite, it can be talking to a data storage and reporting portal like Data InSite^® from Pi or another proprietary portal.

Control InSite is cloud based meaning it is accessible from any internet enabled device anywhere in the world, meaning you can access it without even getting into your car or standing in front of the analyser. This feature is one of the biggest advantages of Control InSite and has been particularly useful during COVID, a time when reducing the number of site visits has been of utmost importance.

CRIUS^®4.0 vs CRIUS^® – what’s the difference?

What does MQTT mean to me?

• Any data-enabled SIM card works with our modems
• Emails and SMS alarms are much cheaper than before
• Much easier to connect to a LAN (Local Area Network)
• Security is enhanced with encrypted data
• The ‘service’ file which details the configuration of the CRIUS^®4.0 is readable and downloadable remotely
• Connection to others’ data portals provides REAL TIME, LIVE DATA.

So what is Industry 4.0 (and Water 4.0 and the Internet of Things and SMART and DIGITAL technology)?

The main principles put forward were based on;

• Interoperability – everything should be able to talk to everything else.
• Information Transparency – the physical world should be able to be recreated virtually to allow for testing and modelling.
• Technical Assistance – information should be presented in a way that supports people to make good and fast decisions.
• Decentralisation – after decades of centralisation to things like DCS systems and SCADA systems, the future is to enable as many decisions as possible to be made locally by whatever intelligence (human or machine) is available.

So what is Water 4.0 and SMART and DIGITAL?

So what is the Internet of Things or IoT?

Not convinced that we are in a new Industrial Revolution?

• Controlling chemical dosing – controlling a pump to dose a chemical into a system based on one or more measurements (e.g. chlorine residual and flow rate, please see the PID technical note for more information).
• Recirculation control – controlling a pump to manage the recirculation of a system (most commonly used in pools, please see the VSD technical note for more information).
• Failsafe protocols – complex water systems can go wrong for any number of reasons, and analysers can play a role in making those systems safer. Many pumps will output digital alarm signals when they detect a fault, alerting the dosing systems that something needs attention, and to stop dosing the chemical. Dosing into a water system which is not recirculating can lead to dangerous overdosing, and also wastes chemicals leading to increased costs.
• Duty rotation, or n+1¹ back-ups – in larger systems, pumps may be rotated in order to increase pump longevity or have a back-up system to rely on in the case of pump failure. Having a back-up, or n+1 system, can often reduce downtime significantly, and so is very useful in production lines where downtime can lead to large cost increases.

Power switching relay based control

Volt Free Contact (VFC) Control

Analogue Control

SMART and DIGITAL control

Pi’s Multi-Parameter Controllers

Pi’s CRIUS^®4.0 Controller

Pi’s CRONOS^® Controller

Advantages of Pi’s Multi-Parameter Systems

1. Space Saving

2. Easier to Use

3. Communications

4. Remote Access

CoagSense Coagulation Controller

Process Instruments (Pi) are increasingly seeing water engineers and technicians relying on their PLC’s PID auto-tune feature. Many are becoming frustrated that the auto-tuners are unreliable when it comes to water processes. Sometimes the auto-tuned PID settings work, but then something changes in the process and the PID control no longer functions correctly.


In this Focus On, Pi aims to outline how PID auto-tuners work and why they are often unsuitable for complex water treatment processes. We also give a brief introduction to some of the principles of tuning a PID manually.


Did you know that…

…auto-tuners are not effective at tuning processes with long loop times?

…the CRONOS^® and CRIUS^®4.0 have many built-in PID safety features to make control easier and safer?

…PID loops can often be tuned remotely, meaning huge savings on site visits and travel time?

What is PID tuning?

A Proportional – Integral – Derivative (PID) controller is a control loop feedback mechanism widely used in industrial control systems. PID controllers allow a system to continuously and automatically modulate a control mechanism (e.g. a dosing pump, a valve, motor speed), to attempt to achieve a desired setpoint.


There are a myriad of ways that a PID controller can be ‘tuned’. In a very basic PID controller, the operator can choose how much of their control should be based on P, I and D. In reality, D is almost never required in water processes due to the nature of the control loop.


This is generally what ‘auto-tuners’ undertake. They make small changes to the ratio between P, I and D control, track the response, decide if the change is good or bad, and then change again.

What is the auto-tune doing?

So what the auto-tuner is doing is changing, measuring, and changing again; which can work perfectly on processes with a very short loop time (time between a change and a response from the system), the auto-tune making many changes in a short amount of time. The changes cumulate into a ‘tuned’ PID system.

On the right is an example system of a PID auto-tune.


In the diagram, we can see that for the system to work, the box in red is a crucial part of the process. If the change brought on by the PID auto-tuner isn’t visible quickly enough, it may affect the way the auto-tuner categorises the change (good or bad), or won’t give the auto-tune the opportunity to make enough iterative changes to bring a complex water system under control.

The good news

There is good news for water technicians and engineers and that is that Pi are here to help. All our salespeople are application specialists and are all capable of helping you manually tune a PID controller for your processes. Our CRONOS^® and CRIUS^®4.0 controllers are both capable of delivering excellent control in many processes, and have many built-in PID features to help make your process more controlled, robust and safe.

Where to start with PID tuning

In many ways, the auto-tuners mimic plant engineers making adjustments and tuning their PID settings. They simply lack 2 key components;

• Patience – because the loop times are so long, it will take time to tune a PID loop.
• Context – no auto-tuner can account for blocked dosing lines, or 2 identical pumps that are improperly calibrated and output different volumes, or seasonal changes in measured parameter concentrations. Context is incredibly important in tuning a PID loop.

With this in mind, here is how our engineers approach PID tuning on our instruments;

1. Check the measurement and output method are all working properly. This includes any calibration on the probes and on the pumps as well as checking that the dosing lines are clear.
2. Consider the loop time and change the PID’s Update Delay. This changes how often the PID algorithm makes a change to the output.
3. Start small and ramp up. Start with the P control and slowly increase the P factor until it is changing the measurement in a satisfactory timeframe. If you can get a good level of control with just P then that’s excellent. There is often no need to overcomplicate things past this. The addition of I and D components is often unnecessary.
4. If you have wild or erratic control lower the P until the control is stable, even if it doesn’t reach your setpoint then add some I control.
5. Always aim to have I as low as you can get away with, as I can cause more problems with control than it solves.

Once you have the basic P and I ratio sorted, or if you are unable to get the P and I into control, it is worth considering these additional settings which will help make your control scheme more robust and safer.

• Min/Max Output – restricts the range that the PID can work within, which can stop potential over- and under-dosing. This setting may also reduce the ability of the PID loop to respond to changes in the water.
• Start Mode – allows the process to be dosed using a flow proportional value or a manual percentage value, during a predetermined start up period. This is often used to get the process up and running before going into PID control.
• Ramping – smooths the start-up of the process where the error between the measured value and setpoint may be very large (which can cause erratic overshoot and overcorrection).
• Bumpless Transfer – smooths out the process of switching between manual and automatic control.
• Integral Wind Up Protection – puts a limit on the effect of I because I looks at error over time. A very small error over a large amount of time can result in a very large I output resulting in erratic control.
• Overfeed Protection – protects against the failure of other equipment, such as failing pumps or blocked dosing lines. This puts the control into alarm if the controller is calling for dosing but is seeing no change.

How our products can help

Even armed with all this knowledge, PID tuning can be a bit of a dark art. What works on one site may not work on another and even experienced engineers sometimes call us for help.


One of the ways we can help is using our remote access system InSite. Our Remote Access portal (Control InSite) allows people with the appropriate security clearance to make changes to settings and observe measurements from their desk.


Sales Manager, Dr. Rob Paramore, recently described his experience of changing a customer’s PID settings (at their request), whilst talking them through what he was doing on the phone:

What is the problem?

High electricity bills and high CO₂ footprint.

What is the solution?

Process Instruments’ CRONOS^® and CRIUS^®4.0 Controllers with VSD

How does VSD control work?

Swimming Pool Application Savings Data

No. 1 – Human readable service log

No. 2 – Cloning facility

No. 3 – On screen wiring diagrams

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

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

No. 6 – Enclosure

No. 7 – Not enough I/O?

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

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

No. 10 – Control algorithms

What is PID?

What is PID for?

What does PID do?

How is it used?

What are the benefits of PID?

Advanced Features and Safeguards

• 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.

Conclusion