Automating the meter test station
Two years ago Metering International discussed the productivity gains achieved by South Western Electricity Board (SWEB) a UK utility, as a result of re-equipping their meter test station with fully automatic meter test systems from EDI. Since then SWEB’s systems have been further streamlined by applying automation principles to the whole of the meter test station.
The project involved collecting data from all the stages that the meters pass through during their progress through the test station. The data would then be used to control the various activities of the station, and to produce management reports automatically. (Fig 1).
|AREAS CONTROLLED||MANAGEMENT REPORTS|
A number of discussions took place to determine the overall shape of the system and to define operational parameters. This initial definition process was vital, particularly as the final system would radically change the way SWEB processed the repair and recalibration of meters. It would also affect the control of key areas of the meter test station.
The system is based on a distributed network of PCs at various locations with-in the meter test station, connected to a central fileserver and database. The main database is Microsoft SQL Server running under Windows NT. The choice of the operating systems and topology was primarily influenced by EDI’s experience in distributed database systems based on Microsoft solutions, but the system as described could equally well be implemented on any suitable network and operating system. From the beginning a flexible approach was taken so that possible future changes in work practices could easily be accommodated.
The PCs used by the system are mostly Pentium class computers with 16/32 MB RAM. The networking standard is category 5 10BaseT, and the file server is a dual Pentium machine with mirrored hard discs and DAT data back-up.
Data entry into the system is via laser barcode scanners, keyboard or automatically from EDI test systems. All these items are fairly standard and could be selected from a wide range of readily available devices.
The architecture of the system is primarily client/server, using SQL Server as the back end server and Microsoft Access and Visual Basic as the front end clients. Automated direct connections to the database server are also built into the EDI test benches. This means that data from the meter testing process can be inserted automatically into the database. The design of the system can be thought of as a sequential flow controller, where each meter being produced passes from one process to another under control of the system. Careful checks can therefore be made on each meter, to ensure that all the necessary operations have been carried out in the correct order. As an example, the system would not allow a meter to progress to the testing stage until it had been repaired and inspected.
THE SYSTEM IN USE
A typical management information screen is shown in Fig. 2. This display shows the different batches of meter currently in the test station. For each batch there is information about its current status, how much the batch is costing to produce and also how many meters have been rejected from the batch. The reject box for the first batch is red in this example. This is an indication that the level of rejected meters from this batch is high and that the batch warrants further quality sampling.
The system contains several similar screens which give an instant management overview of the work in progress. These displays are updated in real time as more data is entered.
Work scheduling displays for production staff are also provided. An example of this is a display which shows the QA inspector all the pending meter inspections, with details of the level of inspection to be implemented and the length of time the meters have been ready for inspection.
Extensive use is made of barcode scanners to speed up data entry and to minimise error. All the meters produced by SWEB are bar-coded at a very early stage of production, using a connected system from EDI. This means that the status of each meter can frequently be entered into the system without error and without incurring a large unnecessary overhead in the production process.
The barcodes are also used during the quality inspection process. When sample testing is carried out on batches of meters, it is important that the correct meters are inspected. By scanning each inspected meter, the system can ensure that the meters belong to the correct batch and can log the exact time and date of the sample test.
Managing stores is an important part of the system. Two distinct areas a recontrolled – the technical stores, where parts used for meter refurbishment are held, and the main finished meter stores, which hold stock ready for dispatch .
In the technical stores the system tracks the usage of each type of part , and makes predictive suggestions about ordering replacement stock . Management reports are also provided regarding the total stock value and holding.
It is important to dispatch the stock of meters in the finished meter stores in the correct order. The system ensures that meters which have the shortest remaining certification time are dispatched first. Deliveries to the various customers of the test station are automatically controlled so that each customer has a maintained minimum stock level. This is useful in that potential areas of stock shortage are identified at an early stage and steps can be taken to avoid future problems.
Access to each production process within the test station is controlled by the system, so that only suitably authorised staff are permitted to carry out each production task. Before starting a task each operative must log onto the system. This allows the system to calculate exact production costs based on actual time spent on each batch of meters.
The test station control system is now in place and fully operational, and several extensions and enhancements are already being discussed. One thing that is certain is that the meter test station at Newton Abbot will continue to be one of the most technically advanced in the world.