Controller

As described in the section on Advanced Pressure Management, the controller continuously adjusts the APV to give the optimum value of P2 using its control algorithms. These self-learning control algorithms are updated and downloaded to the controller daily.

In order to improve battery life, the APV is only adjusted when the difference between the actual value of P2 and the optimum value of P2 as calculated by the algorithm exceed a threshold known as a dead-band. The value of the dead-band is calculated for each DMA during setup to give the optimum trade-off between water saving and battery life.

The controller also continuously records the data required to update the algorithm and for reporting. This normally includes P1 and P2 pressures and flow rate Q. P1 and P2 are taken from pressure tappings on the PRV and Q is taken from the DMA flow meter. The data is stored in the controller's 2Mb memory before being transmitted daily to the i2O server over the GSM network. In those cases where the GSM network is not available, the data can be downloaded manually to a PC or PDA using Bluetooth.

Key features

Robust and water-proof - The environment in which the controllers are installed is very demanding with high levels of moisture, temperature variation, vibration and flooding. All controllers have robust and watertight enclosures to IP68 and have been thoroughly tested in the harshest of environments.

Watchdog - A separate stand-alone circuit called a watch dog constantly monitors critical parts of the system. If these were to fail, the watch dog circuit would put the system into safe mode. In safe mode, P2 is maintained at a fixed, pre-determined level which would provide adequate water supply to the whole DMA until the system could be repaired.

Manual over-ride - There is scope for a water company service engineer without specialist knowledge of the system to make pressure adjustments in response to a complaint or problem. This is done by pressing a simple button on the controller which can increase the pressure in one meter pressure increments. 

High Accuracy - Unlike most conventional loggers or controllers which normally have a resolution of 0,5m, the controller measures pressure with a resolution down to 0,05m. This enables more accurate measurement of P1 and P2 and improved pressure control.

Large memory - At 2Mb, the unit has a much larger memory than most conventional loggers or controllers. This is particularly important if GSM communication is not reliable due to weak signal strength. It also enables fast logging of P1 and P2 to take place.

Fast logging - The interval over which the unit measures P1 and P2 can be adjusted remotely from 0,1 sec upwards. By default, the system generates 1min data but regular periods of faster logging can be programmed in order to detect any pressure transients or spikes in the system. Fast logging also gives valuable information on the condition and performance of the PRV.

Advanced power management - Remaining battery life is one of the parameters that is calculated and reported on regularly. This gives enough warning to replace batteries during planned maintenance or inspection visits. An alarm is also sent back to the server once a battery change is needed urgently.

Should the main battery fail or become empty, the unit switches automatically to its back-up battery while at the same time switching into safe mode. Data continues to be recorded in the unit's 2Mb memory and no system parameters or settings are lost, but there is no further transmission or pressure adjustment until the main battery is replaced.

Low power consumption - A number of design strategies have been employed to achieve exceptionally low power consumption. The length of time between battery changes depends on the number of data transmissions per day and the number of times the pressure is adjusted. A special algorithm is used to calculate the optimum pressure adjustment strategy for each DMA. It does this by understanding the trade off between battery life and the fineness of adjustment of P3 pressure. Based on an average of 96 pressure adjustments/day and one data transmission per day, the battery life would typically be over five years.

Condition monitoring of the PRV - The controller also monitors the performance of the PRV. This can often provide early warning of problems which can be fixed before customers are affected.  For example, one of the most common problems is a blocked filter in the pilot valve bypass loop. By monitoring the pressure drop across the filter, the controller can send out an alarm when it is time to clean or replace the filter. The controller also prevents the PRV, where possible, from operating outside its normal operating range, which prevents damaging cavitation or instability from occurring. 

Condition monitoring of the flow meter - The system relies on continuous, consistent flow data from the installed flow meters. However, these can occasionally fail or lose accuracy. The controller has two independent methods of checking the performance of the flow meter. Firstly, it measures the flow rate through the PRV and compares this to values provided by the flow meter. Secondly, the controller can identify any erratic or obviously erroneous readings. If a faulty flow meter is detected by either method, the system is immediately put into safe mode and an alarm transmitted.

Flow meter compatibility - The controller can interface to any flow meter that generates a pulse using either closing contacts (typically a reed switch) or open-collector.

Additional inputs - The controller also has two further 4-20mA inputs which can be used to collect additional data.

HTTP protocol - All transmissions to and from the controller are made using the standard HTTP protocol. For setting up or manually retrieving data, it may sometimes be necessary to connect a PC or PDA to the controller via Bluetooth. The benefit of using HTTP is that the PC or PDA does not need any proprietary software. It can view or send data using a standard internet browser such as Internet Explorer. Data files can also be transferred easily to and from the controller using Internet Explorer.

GPRS - Where there is an adequate GSM signal, the controller and the P3 and AZP sensors will use GPRS to communicate with the central server. This enables them to transmit and receive enough data each day to update the control algorithms and for reporting purposes. The GPRS transmission is initiated by the sensor or controller once each day.

SMS - Where signal strength is limited, the controller may use SMS to communicate with the central server as an alternative to GPRS.

Bluetooth - It may sometimes be necessary, during set up or if GSM is not available, to connect a PC or PDA directly to the sensor or controller. Bluetooth makes this very convenient as the sensor or controller does not need to be disturbed or uninstalled nor do any covers need to be removed to access physical connectors.

Antenna technology - The latest antenna technology has been used to develop a custom antenna. This usually enables the antenna to be mounted within a valve chamber. However, in areas with low signal strength, a remote antenna can be used instead. This can be installed in a variety of different ways depending on the environment. Common solutions are to mount the antenna on a lamp-post or in a bollard at the side of the road.

Alarms - The controller can send real time alarms directly to an email address or mobile phone as well as the central server. A variety of alarm conditions can be pre-programmed such as low pressure, PRV or flow-meter failure etc.