Parts in the Database

One method of fixing inconsistencies between the schematic and database is to delete the offending part from the schematic, find the correct part in the database, and then place that part in your schematic. A second method is to link the part to the database. Here, we will show this second method. 

Open the schematic and zoom in around the resistor. Click the LEFT mouse button on the resistor graphic to select 

With the resistor selected, click the RIGHT mouse button on the graphic and then select Link Database Part  

The Link Database Part window opens and displays all resistors in the database with a value of 1.8k  

When you find the part you want to use, click the LEFT mouse button on the part to select it  

---

We cannot run a simulation with the parts in the database or the parts we download from the Internet, so select either the PC Board Wizard or the Schematic options ... 

We will show two methods for finding parts in the database. In the first method we use the Query tab and search for specific criteria. In the second method, we will find a part number in the Digikey catalog and then immediately find the part since we know the part number. 

Each part in the database has a unique Digikey part number, so the search should find only the part for which you are looking. Double-click on the part to place it in your schematic ... 

SCISEARCH contains bibliographic citations (links) to publications in science and technology. The database represents the electronic online version of the expanded Science Citation Index (SCI) and parts from the Current Contents of the Institute for Scientific Information (ISI). More than 5900 science and technical journals are included in the database with more than 20 million records (October, 2002). Searches can be performed on the bibliographic data, along with where, and how often, an author or publication is dted. 

Statistical Methods for Nonelectronic Reliability, Reliability Specifications, Special Application Methods for Reliability Prediction Part Failure Characteristics, and Reliability Demonstration Tests. Data is located in section 5.0 on Part Failure Characteristics. This section describes the results of the statistical analyses of failure data from more than 250 distinct nonelectronic parts collected from recent commercial and military projects. This data was collected in-house (from operations and maintenance reports) and from industry wide sources. Tables, alphabetized by part class/ part type, are presented for easy reference to part failure rates assuminng that the part lives are exponentially distributed (as in previous editions of this notebook, the majority of data available included total operating time, and total number of failures only). For parts for which the actual life times for each part under test were included in the database, further tables are presented which describe the results of testing the fit of the exponential and Weibull distributions. 

In a predictive and reliability maintenance program, it is extremely important to keep good historical records of key parameters. How measurement point locations and orientation to the machine s shaft were selected should be kept as part of the database. It is important that every measurement taken throughout the life of the maintenance program be acquired at exactly the same point and orientation. In addition, the compressive load, or downward force, applied to the transducer should be the same for each measurement. 

Most computer-based systems require data-acquisition routes to be established as part of the database setup. These routes specifically define the sequence of measurement points and, typically, a route is developed for each area or section of the plant. With the exception of limitations imposed by some of the vibration monitoring systems, these routes should define a logical walking route within a specific plant area. A typical measurement is shown in Figure 44.15. 

Alert and alarm limits The microprocessor should include the ability to automatically alert the user to changes in machine, equipment or system condition. Most of the predictive maintenance techniques rely on a change in the operating condition of plant equipment to identify an incipient problem. Therefore, the system should be able to analyze data and report any change in the monitoring parameters that were established as part of the database development. 

The primary difficulty in using the SOM, which we will return to in the next chapter, is the computational demand made by training. The time required for the network to learn suitable weights increases linearly with both the size of the dataset and the length of the weights vector, and quadratically with the dimension of a square map. Every part of every sample in the database must be compared with the corresponding weight at every network node, and this process must be repeated many times, usually for at least several thousand cycles. This is an incentive to minimize the number of nodes, but as the number of nodes needed to properly represent a dataset is usually unknown, trials may be needed to determine it, which requires multiple maps to be prepared with a consequent increase in computer time. 

The second part of the database contains reactions for the various secondary species, minerals, and gases. These reactions are balanced in terms of the basis and redox species, avoiding (to the extent practical) electron transfer. Species and minerals containing ferric iron, for example, are balanced in terms of the redox species Fe+++,... 

In this approach accident cases and design recommendations can be analysed level by level. In the database the knowledge of known processes is divided into categories of process, subprocess, system, subsystem, equipment and detail (Fig. 6). Process is an independent processing unit (e.g. hydrogenation unit). Subprocess is an independent part of a process such as reactor or separation section. System is an independent part of a subprocess such as a distillation column with its all auxiliary systems. Subsystem is a functional part of a system such as a reactor heat recovery system or a column overhead system including their control systems. Equipment is an unit operation or an unit process such as a heat exchanger, a reactor or a distillation column. Detail is an item in a pipe or a piece of equipment (e.g. a tray in a column, a control valve in a pipe). 

SGX uses two bar codes to track samples. The first identifier is the 2D bar code on the pin bases, which are used multiple times to moimt individual crystals. The second identifier, a ID bar code, is placed on the vials in which crystals are shipped to the beamline. This barcode is unique to the crystal and, imlike the base, is not reused. The device used to read the barcodes is shown in Fig. 12.3. This system requires that the 1D barcode, which links the physical crystal with its description in the database, constitutes part... 

The Digikey database is desirable because if you place a part from the database in your schematic and generate a BOM from that schematic, the BOM will contain the Digikey order numbers for all parts available from Digikey. You can then easily order the needed parts. If you do not wish to use this feature, you can choose to use only the parts in your own portion of the database. 

The parts available in the database and the parts that can be downloaded from the Activeparts web site do not contain PSpice models, so we cannot use these parts to run a simulation. When you create a project, you should select either the Schematic or PC Board Wizard option. Run Capture CIS and then select File, New, and then Project to create a new project ... 

With over 70,000 parts in the Digikey database, finding the part you need can be a challenge. Fortunately, the Capture CIS provides tools to help you search for parts. To place a part on your schematic, select Place and then Database Part from the Capture menus ... 

You can scroll through the list if you like. Hundreds of capacitors are contained in this list. To select a part, click the LEFT mouse button on the line in the database you want to select. If the line is highlighted in green, then the part is correctly linked to a graphic symbol in one of the symbol libraries. If a symbol and PCB layout footprint are found, they will be displayed in separate windows ... 

A footprint is not displayed because the parts in the Digikey database do not have footprints associated with them. To place the selected part in your schematic, click the RIGHT mouse button on the highlighted part and then select Place Database Part ... 

The Part Manager tells us whether the part information in our schematic is consistent with the part information in the database. As an example, we will change the value of the 1.5k resistor to 1.8k ... 

The part listed in the database is part number pl.5ketr-nd, which is a 1.5k resistor. In the schematic, the value is 1.8k, so the schematic information is inconsistent with the database information. If we create a BOM with this schematic, it will be incorrect. Capture CIS provides a facility for detecting these inconsistencies. 

The option to save the part information to your database is selected. Saving the part in your database will allow you to place the part from your database the next time you need it rather than find the part on the Internet. Saving the part to your database also allows you to easily build up a company database of parts. 

---