【正文】 d the setup, data loggers can run as standalone devices, much like a recorder. They store data locally in internal memory, which can acmodate 50,000 readings or more. PC connectivity makes it easy to transfer data to your puter for indepth analysis. Most data loggers are designed for flexibility and simple configuration and operation, and many provide the option of remote site operation via battery packs or other methods. Depending on the A/D converter technique used, certain data loggers take readings at a relatively slow rate, especially pared to many PC plugin cards. Still, reading speeds of 250 readings/second are not unmon. Keep in mind that many of the phenomena being monitored are physical in nature — such as temperature, pressure and flow — and change at a fairly slow rate. Additionally, because of a data logger39。 while you can use multiple DMMs, the system will quickly bees bulky and awkward. Accuracy is dependent on the transcriber39。Selecting the Right Data Acquisition System Engineers often must monitor a handful of signals over extended periods of time, and then graph and analyze the resulting data. The need to monitor, record and analyze data arises in a wide range of applications, including the designverification stage of product development, environmental chamber monitoring, ponent inspection, benchtop testing and process troubleshooting. This application note describes the various methods and devices you can use to acquire, record and analyze data, from the simple penandpaper method to using today39。s college students are much more likely to use an automated process and analyze the data on a PC Today, numerous options are available for gathering data. The optimal choice depends on several factors, including the plexity of the task, the speed and accuracy you require, and the documentation you want. Data acquisition systems range from the simple to the plex, with a range of performance and functionality. Pencil and paper The old pencil and paper approach is still viable for some situations, and it is inexpensive, readily available, quick and easy to get started. All you need to do is hook up a digital multimeter (DMM) and begin recording data by hand. Unfortunately, this method is errorprone, tends to be slow and requires extensive manual analysis. In addition, it works only for a single channel of data。t perceive small variations with the input signal. Furthermore, the electrical environment inside a PC tends to be noisy, with highspeed clocks and bus noise radiated throughout. Often, this electrical interference limits the accuracy of the PC plugin card to that of a handheld DMM .These cards also measure a fairly limited range of dc voltage. To measure other input signals, such as ac voltage, temperature or resistance, you may need some sort of external signal conditioning. Additional concerns include problematic calibration and overall system cost, especially if you need to purchase additional signal conditioning accessories or a PC to acmodate the cards. Taking that into consideration, PC plugin cards offer an attractive approach to data acquisition if your requirements fall within the capabilities and limitations of the card. Data loggers Data loggers are typically standalone instruments that, once they are setup, can measure, record and display data without operator or puter intervention. They can handle multiple inputs, in some instances up to 120 channels. Accuracy rivals that found in standalone bench DMMs, with performance in the 22bit, accuracy range. Some data loggers have the ability to scale measurements, check results against userdefined limits, and output signals for control. One advantage of using data loggers is their builtin signal conditioning. Most are able to directly measure a number of different inputs without the need for additional signal conditioning accessories. One channel could be monitoring a thermocouple, another a resistive temperature device (RTD) and still another could be looking at voltage. Thermocouple reference pensation for accurate temperature measurement is typically built into the multiplexer cards. A data logger39。監(jiān)測、記錄和分析數(shù)據(jù)在大范圍內(nèi)的應(yīng)用趨勢上升，包括設(shè)計 檢定產(chǎn)品發(fā)展?fàn)顟B(tài)、環(huán)境的監(jiān)測、組成物的檢驗、benchtop 測試和處理故障檢查。在這種情況下，操作者可能采用視訊遙控，通過大量檢測數(shù)據(jù)傳輸?shù)綑z測室，在那里收集、存儲和處理數(shù)據(jù)。隨著技術(shù)的發(fā)展，通過電子設(shè)備，這個過程已經(jīng)得到簡化和變得比較精確、多用途和可靠。舉例來說 ,在 40 年以前 ,在一個著名的學(xué)院實 驗室中 ,為追蹤用青銅做的坩堝中的溫度上升情況的裝置是由熱電偶、繼電器、查詢臺、一捆紙和一支鉛筆。 鉛筆和紙 用鉛筆和紙的舊方式對于一些情形仍然是可行的，而且它便宜、易獲得、快速和容易開始。精度取決于謄寫器的水平，并且你可能需要自己動手依比例輸入。他們提供數(shù)據(jù)的長備紙記錄 ,因為數(shù)據(jù)是圖解的格式 ,他們易于現(xiàn)場采集數(shù)據(jù)。在多通道內(nèi)較長時間的監(jiān)控，記錄儀能發(fā)揮很好的作用，除此之外，它們的價值得到限制。 數(shù)字掃描傳多用表 一些 benchtop DMMs 提供可選擇的掃描能力。外部的 PC 機(jī)通常處理數(shù)據(jù)采集和分析。因為卡片本質(zhì)上是計算機(jī)的一部分 ,建立測試是容易的。這些插件卡片也測量一定范圍的電壓。 數(shù)據(jù)電子自動記錄儀 數(shù)據(jù)電子自動記錄儀是典型的單機(jī)儀器，一旦配備它們 ,就能測量、記錄和顯示數(shù)據(jù)而不需要操作員或計算機(jī)參與。 使用數(shù)據(jù)電子自動記錄儀的一個好處就是他們的內(nèi)部監(jiān)測信號。內(nèi)設(shè)智能數(shù)據(jù)電子自動記錄儀幫助你設(shè)定測量周期和具體指定每個通道的參數(shù)。大多數(shù)數(shù)據(jù)電子自動記錄儀可設(shè)計為柔性和簡單的組態(tài)和操作 , 而且經(jīng)由電池包裹或其它方法，多數(shù)提供遠(yuǎn)程位置的操作選項。此外，因為數(shù)據(jù)電子自動記錄儀的監(jiān)測精度 ,多量且平均閱讀沒有必要，就像它們經(jīng)常在 PC 記插件卡片一樣。前端運轉(zhuǎn)的效率是非常高的 ,能與速度和精度與最好的單機(jī)儀器匹敵。 數(shù)據(jù)電子自動記錄儀的應(yīng)用 好的、成本低的數(shù)據(jù)電子自動記錄儀有合適的通道數(shù)（ 2060 通道）和掃描速率相對低但對于多數(shù)工程師的普遍應(yīng)用已足夠。使用者打算購買數(shù)據(jù)采集裝置或系統(tǒng)的第一步?jīng)Q定于身邊的任務(wù)和想要的輸出，然后選擇類型和儀器符合他們的標(biāo)準(zhǔn)的范圍。s petitive, fast evolving world. In the last several years, many firms have spent millions of dollars in building enterprisewide data warehouses. Many people feel that with petition mounting in every industry, data warehousing is the latest musthave marketing weapon —— a way to keep customers by learning more about their needs. “So, you may ask, full of intrigue, “what exactly is a data warehouse? Data warehouses have been defined in many ways, making it difficult to formulate a rigorous definition. Loosely speaking, a data warehouse refers to a database that is maintained separately from an anization39。大量組織機(jī)構(gòu)已經(jīng)發(fā)現(xiàn)，在當(dāng)今這個充滿競爭、快速發(fā)展的世界，數(shù)據(jù)倉庫是一個有價值的工具。寬松地講，數(shù)據(jù)倉庫是一個數(shù)據(jù)庫，它與組織機(jī)構(gòu)的操作數(shù)據(jù)庫分別 維護(hù)。四個關(guān)鍵詞，面向主題的、集成的、時變的、非易失的，將數(shù)據(jù)倉庫與其它數(shù)據(jù)存儲系統(tǒng)（如，關(guān)系數(shù)據(jù)庫系統(tǒng)、事務(wù)處理系統(tǒng)、和文件系統(tǒng)）