The L8 Legionella regulations insist on the proper measurement and thorough monitoring of all water tanks, including of course microbiological assays. Water tanks need to be monitored for humidity, temperature and level (or, more importantly, volume. A ‘continuous’ measurement of level or volume has therefore become crucial to estates managers, and if that measurement can be non-contacting and therefore non-contaminating, so much the better.
While a simple float switch or ball valve will switch on a fixed or maximum level, and can be used for maintenance of level at a point, continuous level measurement will provide a wealth of information for the system managers. At a glance, or even automatically, managers can be informed of any abnormalities in operations or warned of leaks; the volume of water in a tank can be measured to aid accurate dosing of anti-microbials or disinfect the system.
Pulsar Process Measurement Ltd provide a number of options for system managers looking to introduce non-contacting continuous level measurement to site water tanks. Based on well-proven ultrasonic technology, instruments in the Pulsar range range from self-contained, stand-alone instruments through ‘intelligent’, fieldbus units through to more complex control systems that will control pumps or valves in response to a variety of parameters including level or volume, change of level and more. In most cases, calculations are automatically made to convert level to volume, based on a variety of pre-programmed tank shapes.
Ultrasonic level measurement is based on the ‘time of flight’ of sound pulse travelling from a transducer to the water surface and back again. The sound pulse is generated by ‘exciting’ a piezo-electric crystal built into a transducer mounted above the water surface, causing it to emit an ultrasound signal. That pulse then re-excites the crystal when it echoes back from the water surface. Digital signal processing then creates the output. The distance from the transducer to the furthest measurement point (typically the bottom of the tank) determines the choice of transducer, with options from 3m maximum range all the way through to 50m, typically used on very deep storm tanks.
Outputs vary; at the simplest level, most instruments include an LCD display that can be read and manually monitored, alternatively/additionally, a 4-20mA output proportional to level or volume can be generated; RS485 digital communications in Profibus, Modbus and Hart versions, volt-free contacts to operate alarms or valves are all possible. Data can be logged either on-board or remotely. Units can be programmed, cloned and signals analysed from a PC.
A versatile technology, then. The Pulsar range exemplifies the available equipment:
IMP is Pulsar’s ‘entry-level’ device. Easily installed and programmed either via a PC or by on-board buttons, IMP is simple in application but sophisticated behind, with digital signal processing making sure that the measurement is reliable and accurate. Available in 3, 6 and 10m range versions.
For sites operating fieldbus systems, Pulsar’s range of self-contained Intelligent Transducers operate under either the HART or Profibus PA protocols. Standard programming tools may be used to set up and interrogate the systems, or Pulsar’s own software is available.
For all other controllers, transducers from the core dB range provide measurement from 3m to 50m, depending on the controller in use. The Blackbox range lacks a built-in display and provides a range of outputs depending on the specific unit chosen; either a pair of relays for alarm or control, or a milliamp output, or indeed a digital RS485 interface. Pulsar’s Ultra 3 and Ultra 5 controllers are sophisticated control systems, with multi-functional displays, menu-based programming and in-built routines to manage pumps or valves, with a choice of either three or five relays built in.
Taken together, Pulsar’s non-contacting ultrasonic level measurement range provides a complete solution for water tank level and volume measurement and control. Designed around the needs of the water and waste water industry, Pulsar is a British company perfectly positioned to supply the equipment, know-how and support to estate and systems managers throughout the institutional, business, process and retail sectors.