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Customised Pattern Approved Flow Metering Systems
The problem with traditional Flow Metering Systems that require Weights and Measures pattern approval for trade, is that any small change in the way the system operates may require that the approval process be applied again. This means that either a system has to be so versatile (and expensive) to satisfy a wide range of customers, or that a number of versions have to be individually approved, also leading to increased costs. An innovative concept of dividing such a measurement system into a common pattern approved part, together with a customisable section to satisfy the specific requirements of individual users, is now possible.
This type of configuration is recognised by Weights and Measures authorities as including what is known as an Alibi Controller. This is so called to convey that it can be proved not to have performed any illegal act. The unit is designed to ensure that every measurement and other activities are recorded in a way that cannot be edited or open to fraud. The pre-programmed Alibi Controller (PD 600 DPI), is connected with the measurement transducer (PD 340 Flow Transmitter) and an Indicator with keyboard (PD 681), for operator visualisation and control, using a single P-NET fieldbus segment (RS 485). This forms the pattern approved and sealed “legal” part of any system. However, because the Alibi Controller contains a second independent P-NET communications port (Light-Link), enables an additional programmable controller (PD 60x) to be attached to the system, but with guaranteed restricted access to any collected measurement or verified calibration data. This means that the way the overall system operates can be designed to suit each customer’s needs, without having to seek further approval. It also means that additional devices, such as input/output modules, can also be included. Because the “legal” part of the system has not been affected in any way, enables this together with the “non-legal” part, to retain its approval for active use.
Sealed Flow Transmitter
The type approval includes the use of the P-NET enabled PROCES-DATA PD 340 Hygienic Flow Transmitter, where access to calibration factors have been electronically disabled and the unit mechanically sealed. This flow meter has been proven to be particularly suitable for use on trucks for the delivery or collection of consumable liquid products, such as milk, beer or wine, where it is essential that an accurate electronic or printable record of any sales transaction needs to be made. The approval also includes the ability to change the sealed flow meter for occasional maintenance or recalibration (validation) by instructed personnel, without the involvement of Weights and Measures officials. This is because it is automatically detected when such a change has been made, where a time-stamped record of such an event is generated for historical analysis, should there ever be any dispute.
The PD 681 Indicator and Keyboard acts as the method of issuing instructions to a driver and for operator input, as well as for inspecting individual alibi records. An important aspect of the approval is that the lowest line of the backlit LCD display is reserved for the exclusive use of the Alibi Controller. The other three lines can be utilised by either the Alibi Controller or another programmed source. The keyboard layout is fixed in terms of particular functions performed by the Alibi Controller, but a number of keys are available for use by a customised controller for specific system operation, e.g. starting a CIP sequence.
It is required that at least one additional programmable controller is included in the system for user defined software. Ideally, this should be a PD 60x DPI module, since it will clip directly onto the same DIN rail as the Alibi Controller using Light-Link. Further controllers and I/O modules can also be connected in this way to form a very compact system. Since DPI modules offer a variety of port types (RS232, RS485, Ethernet), means that other ancillary equipment such as printers for invoice or receipt generation, GSM modems for collected or route data transfer, or GPS physical location identification, can also be included in the overall system.
· 20,000 transaction log capacity stored in non-volatile Flash memory.
· Compact custom designs based on M36 series of modules and PD 340 Flow Transmitter.
· Complete flexibility to connect additional process control equipment.
· By ensuring that the unique Alibi record No. is shown on all printouts, will also include the printer in the type approval.
· Suitable for use with vehicle power supplies and within mobile environments.