As described in the section on Advanced Pressure Management, the controller 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 as the characteristics of the DMA change.
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 using GPRS. 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 in order to ensure that adequate water pressure would be supplied to the DMA.
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 control relationship in one metre pressure increments. An alarm is automatically generated on manual over-ride.
High Accuracy - Unlike most conventional loggers or controllers which normally have a resolution of 0.05m with full temperature compensation. The device calculates average pressures using a high frequency sample rate of as little as 1 second. 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 GPRS communication is not reliable due to weak signal strength. It also enables large log files to be stored if fast logging of P1 and P2 is required.
Fast logging - The interval over which the unit measures P1 and P2 can be adjusted remotely from a minimum of 1 second upwards. By default, the system generates 15 min 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 for i2O 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.
The controller can accommodate 2 primary cells in addition to a back-up cell.
Should the main battery fail or become empty, the unit switches automatically to the second primary cell (if fitted) or to its back-up battery. When switching to the back-up cell the device switches into safe mode. In 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 100 pressure adjustments/day and one data transmission per day, the battery life would typically be over five years.
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.
Temperature - The controller and P3 sensor both measure transducer temperatures and the temperature inside the enclosure. If temperatures fall below a pre-set threshold and there is risk that the water at the pressure transducers may freeze, the device will generate an alarm and set the APV to a safe pressure to protect against possible false readings. Temperatures are also logged and transferred to the i2O server with the pressure and flow data. The i2O system can be optionally supplied with remote pressure sensors if there is a significant risk of freezing temperatures in the chamber.
Additional inputs - The controller also has the option to fit two 4-20mA inputs, a USB interface, and a RS232 serial port.
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 (eg Internet Explorer, Mozilla Firefox). Data files can also be transferred easily to and from the controller online.
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. For security, the GPRS transmission is always initiated by the sensor or controller on a scheduled basis.
SMS - Where signal strength is limited, the controller can still use SMS to transmit alarms.
Bluetooth - It may sometimes be necessary, during set up or if GPRS 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 - A high performance antenna is used which 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 high or low pressure and flows, PRV or flow-meter failure etc.