外文翻譯--正確選擇數(shù)據(jù)采集系統(tǒng)(編輯修改稿)
2025-02-04 08:16 本頁面
【文章內(nèi)容簡(jiǎn)介】 l 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. 7. 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。s builtin intelligence helps you set up the test routine and specify the parameters of each channel. Once you have pleted 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。s superior measurement accuracy, multiple readings and averaging are not necessary, as they often are in PC plugin solutions. 8. Data acquisition front ends Data acquisition front ends are often modular and are typically connected to a PC or controller. They are used in automated test applications for gathering data and for controlling and routing signals in other parts of the test setup. Front end performance can be very high, with speed and accuracy rivaling
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