【正文】 s, strain gauges, and currentoutput devices to PCbased DAQ boards. Signal conditioning improves the accuracy, effectiveness and safety of the measurements, for any type of sensor used in the measurement because of capabilities such as amplification, isolation, and filtering. The National Instruments SCXI product line can supply the signal conditioning and instrumentation front end required for the PCbased DAQ systems. AnalogtoDigital ControlConnecting digital circuitry to sensor devices is simple if the sensor devices are inherently digital in nature. Switches, relays, and encoders are easily interfaced with gate circuits due to the on/off nature of their signals. However, when analog devices are involved, interfacing bees much more plex. Some mechanism is needed to electronically translate analog signals into digital (binary) quantities, and visaversa. An analogtodigital converter, or ADC, performs the former task while a digitaltoanalog converter, or DAC, performs the latter. An ADC inputs an analog electrical signal such as voltage or current and outputs a binary number. In block diagram form, it can be represented as shown in Fig. . Understanding Integrating ADCsIntegrating ADCs provide high resolution A/D conversions, with good noise ideal for digitizing low bandwidth signals,and are used in applications such as digital multimeters and panel meters. They often include LCD or LED drivers and can be used stand alone without a microcontroller host. The following section explains how integrating ADCs work. Discussions include single, dual and multislope conversions. Also, an indepth analysis of the integrating architecture will be discussed.Finally a parison against other ADC architectures will aid in the understanding and selection of integrating ADCs. Integrating analogtodigital converters (ADCs) provide high resolution and can provide good line frequency and noise rejection. Having started with the ubiquitous 7106, these converters have been around for quite some time. The integrating architecture provides a novel and straightforward approach to converting a low bandwidth analog signal into its digital representation. These types of converters often include builtin drivers for LCD or LED displays and are found in many portable instrument applications, including digital panel meters and digital multimeters.SingleSlope ADC ArchitectureThe simplest form of an integrating ADC uses singleslope architecture(Figs. , b). Here, an unknown input voltage is integrated and the value is pared against a known reference value. The time it takes for the integrator to trip the parator is proportional to the unknown voltage (VINT/VIN ). In this case, the known reference voltage must be stable and accurate to guarantee the accuracy of the measurement.One drawback to this approach is that the accuracy is also dependenton the tolerances of the integrator’s R and C values. Thus in a productionenvironment, slight differences in each ponent’s value change the conversion result and make measurement repeatability quite difficult to attain. To overe this sensitivity to the ponent values, the dualslope integrating architecture is used.DualSlope ADC Architecture A dualslope ADC (DSADC) integrates an unknown input voltage (VIN)for a fixed amount of time (TINT), then “disintegrates” (TDEINT)usingaknown reference voltage (VREF) for a variable amount of time (Fig. ). The key advantage of this architecture over the singleslope is that the final conversion result is insensitive to errors in the ponent values. That is, any error introduced by a ponent value during the integrate cycle will be canceled out during the deintegrate phase. In equation form: 。1 如何使用傳感器進(jìn)行信號(hào)檢測(cè)？1 信號(hào)調(diào)理的各個(gè)階段是哪些？1 如何使用SCXI信號(hào)調(diào)理？LabVIEW based Advanced Instrumentation Systems General Signal Conditioning FunctionsRegardless of the types of sensors or transducers that are used, the propersignal conditioning equipment can improve the quality and performance ofthe system. Signal conditioning functions are useful for all types of signals,including amplification, filtering, and isolation. AmplificationUnwanted noise can play havoc with the measurement accuracy of a PCbasedDAQ system. Signal conditioning circuitry with amplification, which applies gain outside of the PC chassis and near the signal source, can increase measurement resolution and effectively reduce the effects of noise. An amplifier, whether located directly on the DAQ board or in external signal conditioners, can apply gain to the small signal before the ADC converts the signal to a digital value. Boosting the input signal uses as much of the ADC input range as possible. However, many transducers produce voltage output signals on the order of mill volts or even microvolt. Amplifying these lowlevel analog signals directly on the DAQ board also amplifies any noise picked up from the signal lead wires or from within the puter chassis. When the input signal is as small as microvolt, this noise can drown out the signal itself, leading to meaningless data.A simple method for reducing the effects of system noise on the signal is to amplify the signal as close to the source as possible, which boosts the analog signal above the noise level before noise in the lead wires or puter chassis can corrupt the signal. For example, a Jtype thermocouple outputs a very lowlevel voltage signal that varies by 50181。1 解釋一下不同類型的傳感器。1 大概解釋下DAC的結(jié)構(gòu)類型。 列出一般的信號(hào)調(diào)理功能。 傳感器的類型有哪些？ 寫出換能器的特性。 傳感器的特征是什么？ 詳細(xì)講解電容式傳感器及其應(yīng)用。 繪制傳感器的原理圖。在幾個(gè)設(shè)備中也要進(jìn)行比較，以證明其性能的霸主地位。對(duì)特征性質(zhì)和這些工具的主要特點(diǎn)進(jìn)行了細(xì)節(jié)劃定。對(duì)特征性質(zhì)和這些工具的主要特點(diǎn)進(jìn)行了詳細(xì)的討論?？偨Y(jié)——在虛擬儀器數(shù)據(jù)采集設(shè)備包含三個(gè)主要階段——數(shù)據(jù)采集，數(shù)據(jù)處理，與數(shù)據(jù)操作。特別地，上電或斷電時(shí)數(shù)據(jù)信號(hào)不應(yīng)該被應(yīng)用到DAC輸入端。12位MAX530工作在雙極性電源并直接提供雙極性輸出把電壓。如需要雙極性輸出級(jí)，該復(fù)位可以在電壓0V到一半的最大輸出電壓（中端）間調(diào)節(jié)。MAX5120/MAX5170設(shè)備可以抑制這種脈沖。如果沒有這種功能，DAC輸出簡(jiǎn)單地遵循在上電時(shí)的電源電壓，直到集成電路開始工作。這種安排有助于通過兩個(gè)外部電阻設(shè)置一個(gè)單獨(dú)的增益（）。輸出級(jí)DAC的輸出級(jí)可以被設(shè)計(jì)為提供一個(gè)電壓輸出或電流輸出，