《methods》由会员分享，可在线阅读，更多相关《methods（7页珍藏版）》请在金锄头文库上搜索。
1、ECE 4901 Spring 2009LVDT DIGITIZATION OF A LINEAR VARIABLE DIFFERENTIAL TRANSFORMER: PROJECT PROPOSALTeam Members: Nicolae Caldari (Electrical Engineering) Kenneth Cowette (Computer Engineering) Eric Heiden (Computer Engineering)Advisor: John ChandySponsor: Trans-tek Inc. http:/ (860) 872-8351Conten
2、ts 1. Summary 2. Background 3. Objective 4. Solution I. Technical Specifications II. Methods 5. Timeline/Milestones 6. Budget1. Summary:The goal of our project is to alter a Linear Variable Differential Transducer (or “LVDT”) which outputs an analog signal so that it outputs a digital signal. Throug
3、h the use of a microcontroller, direct digital output LVDTs are able to achieve a much higher degree of precision than traditional analog models. The finished product will be small enough to fit in the cylindrical housing of the LVDT (Outer Diameter .75”), will have either (or possibly both if time
4、allows) a USB or RS-485 output connection, calibration software, and monitoring software. In this proposal we will provide background on LVDTs, our objectives for the project, the basic intent of our project design, and specifics on our timeline and budget for the project.2. Background: A Linear Var
5、iable Differential Transformer, or LVDT, is a device which measures linear displacement through the use of solenoidal coils positioned (in one of several ways) throughout a cylindrical tube. A typical LVDT is displayed in Fig. 1 below.Fig. 1: The exterior of a basic LVDT. (http:/ are three coils ins
6、ide the housing: A primary coil, located in the center, and two secondary coils, one on either side of the shaft. The primary coil is excited with an alternating current causing an induced voltage in each of the secondary coils. A cylindrical ferromagnetic core, shown above on the right side of the
7、figure, is attached to the object whose position is being measured. This magnet slides along the axis of the tube, changing the mutual inductances to change in each of the secondary coils. These coils are connected in reverse series, thus the output is the difference in voltage between the two. When
8、 the coil is perfectly centered the mutual inductances are equal and therefore the difference is zero. As the magnet is moved from the center position it is causes a greater voltage in the closer coil and a smaller voltage in the further coil, thus producing a “displacement” in voltage.1 LVDTs are u
9、sed in countless applications throughout the world. A Robotic arm uses an LVDT (or most likely several) to measure its position. Some ATM machines use small stroke LVDTs to sense how many dollar bills are being deposited or dispensed. While analog LVDTs work quite well, they require difficult and in
10、accurate onsite calibration. Through the use of internal memory and a microprocessor, we plan on eliminating the need for such calibration, which will result in significantly greater accuracy we hopefully should be able to achieve 10 times greater accuracy.Solution: Technical Specifications Electric
11、al Parameters Input Voltage 6-30V DC Input Current 50mA Output USB and/or RS-485 Output UnitsMetric and Inches Linearity +/- 0.05% Temperature Coefficient +/- 0.01 Reading/Deg FEnvironmental Parameters Operating Temperature-13 to 185 Deg FMechanical Parameters Durability: Housing for LVDT should be
12、sturdy to protect circuitry. Size: Relatively sized to match competitors, depending on stroke width. Weight: Also, similar to match competitors, depending on stroke width. Software Parameters Windows PC using Visual Basic to program Language. Friendly user GUI to ensure easy use of the software and
13、its components. Ability to choose unit measurement and automatically calibrate accordingly. No need for on-site calibration desired. MIN, MAX, and TIR functions to store the minimum, maximum, and zero set values, respectively. Tare and zero function allows unipolar and bipolar output. Live display o
14、f displacement1 Description of how an LVDT functions paraphrased from http:/en.wikipedia.org/wiki/LVDTDesign: Our team came up with 2 designs for our Digital LVDT. The designs are very similar to each other. The only difference is in the processor we are using. One processor has an internal USB/USAR
15、T interface. The other one has an internal EEPROM and USART interface. The first design has the same amount of chips for both USB /RS485 outputs. The second design uses one less chip if the output of the device is USB. First Design: A 16 bit A/D chip converts the input voltage into digital signal, a
16、nd inputs it to a Pic16F870 microcontroller. This 28 pin microcontroller has an internal EEPROM and a USART interface. If USB is chosen as a type of output, we will use a FT232MB chip to interface with the USB. On the other hand, if RS-485 is chosen as a type of output, we will use a RS232/RS485 converter in or
