The purpose of the P3 sensor is to continuously monitor P3. In cases where there are multiple critical points, a P3 sensor will be installed on each of them. The pressure data is stored in the P3 sensor's 2Mb memory and sent via GPRS once a day to the i2O server. This data is required for creating and continuously improving the algorithms and also for monitoring P3 against P3ref. If P3 falls below P3ref, an alarm is sent immediately to the server.
Key Features
Compact - The P3 sensor at 120mm by 220mm is extremely compact and designed to be installed in small valve chambers or boundary boxes.
Robust and water-proof - The environment in which the P3 sensors are installed can be very demanding with high levels of moisture, temperature variation, vibration and flooding. They may also be installed in chambers in the road which can fill with gravel or sand. Traffic driving over the chamber cover may then transmit considerable loads to the sensor. All P3 sensors are therefore installed in robust and watertight enclosures to IP68 and have been thoroughly tested in the harshest of environments.
High Accuracy - Unlike most conventional loggers which normally have a resolution of 0.5m, the P3 sensor has a resolution down to 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 P3 pressures.
Large memory - At 2Mb, the unit has a much larger memory than most conventional loggers. This is particularly important if GPRS communication is not reliable due to weak signal strength. It also enables fast logging of P3 pressure to take place.
Fast logging - The interval over which the unit measures P3 can be adjusted remotely from 1 sec upwards. In normal operation, the system generates 15min data but regular periods of faster logging can be programmed in order to detect any pressure transients or spikes in the system.
Advanced power management - Remaining battery life is one of the parameters 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. 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 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. Under normal circumstances there would be one transmission per day which would give a battery life in excess of five years.
HTTP protocol - All transmissions to and from the P3 sensors 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 sensor via USB, Bluetooth or GPRS. The benefit of using HTTP is that the PC or PDA 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 sensor online.
GPRS - Where there is an adequate GSM signal, the P3 sensor will use GPRS to communicate with the central server. This enables it to transmit and receive enough data each day to update the main 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 can still use SMS to transmit alarms.
Bluetooth - It may sometimes be necessary, during set up or if GSM is not available, to connect a PC or PDA directly to the P3 sensor. 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 - If pressure goes outside acceptable limits, an alarm is sent in real time direct to a specified mobile phone or email address as well as the central server.