Digital design for computer data acquisition
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In the design of the system, data is first conditioned by the analog channel. Real circuit designing demonstrated that the high-speed data acquisition system of AD based on M bandwidth of analog channel is workable. Li and D. Request Permissions. Bulletin of Science and Technology, , 29 8 : Research on the control logic of continuous high speed acquisition based on PCI bus [J].
Foreign Electronic Measurement Technology, , 28 3 : Research of analog channel in high-speed data acquisition system [J]. Modern Electronic Technique, 24 : All Rights Reserved.
VLSI Systems and Digital Design
Log In. Paper Titles. Analysis of Electrical Field of Overhead Line p. Design and Implementation of Data Acquisition Article Preview. Abstract: High speed analog signals output by test object in the field of testing and controlling is typical. Add to Cart. Applied Mechanics and Materials Volumes Main Theme:. Mechatronics Engineering, Computing and Information Technology. Edited by:. Xu, Bin Li, Q.
Seismic Data Acquisition
Lu, X. The different preparations represent various angles and steep and parallel opposing tooth surfaces incisors.
For most digitizing systems, the latter are generally the most difficult to capture. Older systems might be limited to a certain height or taper of the prepared tooth, whereas newer systems extraoral as well as intraoral digitization do not have these limitations. Computer-aided design CAD and computer-aided manufacturing CAM technologies allow the use of a range of manufacturing methods and materials for dental restorations. Conventionally, high-precision condensation-curing or addition-curing impression materials are used to make dental impressions. Subsequently, dental stone is poured into these impressions.
The resulting gypsum model can be digitized extraorally An ever more widely applied alternative is intraoral digitization 7 , 28 , which allows practitioners to dispense with conventional impressions and gypsum model fabrication. Both methods of data capture have advantages and disadvantages.
Clinical parameters have the greatest impact on the quality of dental impressions These factors, which include moisture saliva, blood , movement of patient and dentist, and restricted space in the oral cavity, can also impede intraoral digitizing. Because of space restrictions, intraoral digitizing devices have a smaller measuring area than extraoral digitizers. As a result, several digital data sets must be obtained and combined to capture more than two to three neighboring teeth when using intraoral digitizing devices.
This process, termed matching, will always introduce a small systematic error to the data of any measuring system. However, conventional impressions of the full arch are also subject to greater deviation than those of single teeth. Furthermore, extraoral digitization always includes the errors introduced by impression and gypsum model-making in addition to the error resulting from digitization CAM precision also depends on the quality of the machining components 1, The individual errors can cancel or mutually reinforce each other. Mixed effects are also possible Such analyses compare a real model with its corresponding virtual CAD model.
Preferably, the real model is made of a directly digitizable material. Powder use can be avoided to reduce translucency or reflection, which will always increase error in the digitizing process 10 , Very high standards for alignment must be set for these analyses. With alignment or registration, data sets are positioned in one common coordinate system with the least possible mean deviation This deviation is usually given in terms of the root mean square RMS error and should be documented for the assessment of systematic error in 3D analysis 5.
Repeated measurement of reference models has been used to analyze the precision of digitizing systems 3 , 9 , 13 , However, geometrically defined reference models are of limited value for analyzing freeform surfaces. According to ISO 13 , definition 3.
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Accuracy is a qualitative concept. Its quantitative counterpart is trueness Precision is calculated as a standard deviation indicating the closeness of agreement among the results obtained when applying the experimental procedure several times under prescribed conditions 10 , Despite the increasing use of dental digitizing systems, studies on their accuracy are lacking 6. The shape and type of tooth to be digitized affect the achievable accuracy, depending on the digitizing system used.
An experimental setup for 3D analysis was used to assess and compare the accuracy of different dental digitizing systems, 10 for extraoral data acquisition plus one system tested a second time using a zoom lens and four for intraoral data acquisition Figure 1 , Figure 2.
Design and Implementation of Data Acquisition System Based on FPGA and High-Speed AD
Analyses were based on two prepared ceramic master dies molar and incisor and their corresponding virtual CAD models. In order to determine its precision, a preparatory study slightly differing in design was conducted. A steel canine instead of the ceramic master dies with a chamfer preparation was used for a series of 10 measurements of a gypsum duplicate die. All measurements were aligned to the CAD model corresponding to the steel canine.
Afterwards, all measurements were three-dimensionally compared with one another using a CAD program geomagic studio and qualify Reverse engineering of ceramic master dies and corresponding virtual CAD models. Using a CAD software program ce. The acquired ODKM97 digital data sets point clouds from the ceramic dies were filtered to remove outliers and stray points.
These reverse-engineered CAD models of the incisor and molar were used to analyze the measuring data from all digitizing systems evaluated Figure 2. Each gypsum die was digitized once. Because all impressions were made at room temperature rather than body temperature, the setting time recommended by the manufacturer was extended by 5 min.
Only flawless gypsum dies were used. Dies with bubbles or pearls were discarded and remade impression and die. The bases of the dies were reduced by dry trimming only, to avoid water contamination of the gypsum. All five molar and five incisor gypsum dies were digitized within 72 h of manufacture with the respective extraoral digitizing system Figure 2. Following common clinical and dental laboratory procedure, system-specific standard provisions were used to improve data quality after digitizing. For all intraoral digitizing systems, the ceramic master dies were used directly for data acquisition, again according to clinical procedure, which does not include impression or gypsum model making.
go site The incisor and the molar were digitized five times with each system. The Lava C. Again, system-specific standard provisions were used to improve data quality after digitizing. Each data set was oriented in its own measuring coordinate system. The error in this alignment was recorded as RMS error prior to the analysis of the quality of fit. The number of single points in each data set, representing the surface of the digitized tooth, depended in part on the size of the tooth.
After the procedure, incisor data sets consisted of 2, to 29, data points; molar data sets comprised 3, to 39, data points. Apart from this sampling, all data sets point clouds or STL-surfaces were used unchanged and exactly as exported by the respective digitizing system. Maximum and mean positive and negative deviations from the virtual CAD master model were calculated Geomagic Qualify. Color-coded graphs Geomagic Qualify were used to show how the calculated differences were spread over the complete die surface, thus revealing strengths and weaknesses of each digitizing system.
The effect of different tooth shape incisor versus molar was also determined Figure 3. Outlier values are more than 1. Systems indicated with the same letters a, b, c show no significant statistical difference. Rather than improving the digitization results, the addition of the zoom lens to the digiSCAN system resulted in decidedly poorer digitizing quality Figure 4a , right. The zoom lens affected the molar measurements more than the incisor measurements.
The insignificant differences between extraoral Figure 4a , left and middle and intraoral digitizing systems Figure 4b in measuring the ceramic master molar can be assessed at a glance with the color-coded graphs.
The ceramic master incisor proved to be more challenging than the molar for most of the digitizing systems examined. Most systems had higher deviations in the incisor data sets than in the molar measurements Figures 5a and b, middle and right. The powder, which had to be applied before using the CEREC Bluecam system, clearly showed in the resulting higher positive deviations Figure 5b , middle. While two generations of the same digitizing system D and D did not render different results for the molar measurements, there was a clear improvement with use of the newer model for the incisor measurements Figure 5a.
The extraoral systems Lava Scan 9. Only D because of the incisor measurements, Results for the mean negative deviations were similar, with best results Only the mean negative deviations of D This experimental setup allowed a broad comparison of different technological concepts for extraoral and intraoral digitizing systems. The method of analysis was developed from a study design originally used to evaluate 3D changes in gypsum dies over time One major advantage of dispersion ceramic dies is their non-reflecting surface, compared with the metal dies used in prior studies 15 , The aspects of the respective clinical procedure were considered implying gypsum duplicate dies for the extraoral systems and digitizing the ceramic master die directly with the intraoral systems.
The small but existing error of impression and gypsum die making of single teeth 30 raises the systematic error in relation to intraoral digitizing.
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However, eliminating this bias from the experimental set-up would have meant to add an error source to the intraoral procedure that is not part of the clinical procedure. At the same time, one of the advantages of intraoral digitizing would have been precluded. Dispersion ceramic dies can be directly digitized without the use of powder unless required by the digitizing technology itself , which reduces the systematic error of the experimental setup 8.
It cannot be ruled out that the ceramic material influenced the results either positively or negatively compared with dentine since especially the presence of water affects the digitizing quality greatly Looking at the quite similar results for single teeth premolars in a clinical trial using the CEREC 3D intraoral digitizing system 27 a system that was not part of the study at hand suggests that the material influence in the in-vitro set-up presented here is probably of minor importance.
In the clinical procedure, knowing the approximate powder layer thickness allows adjustments for these deviations in the subsequent steps of the process chain. Applying the powder as evenly as possible is mandatory for high digitization precision. Powdering is prone to application errors 8.