Lab 9 write-up

Lab 9 write-up - Introduction The purpose of this lab is to...

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Introduction The purpose of this lab is to gain an understanding of the common temperature sensors, and how that information may be used for computer control of the environment. This lab introduces the basic concepts of resistive Wheatstone bridge circuits with a thermistor. In this lab, the system will be calibrated using a standard probe (calibration set) and used to measure the temperature of some objects. The last task will be to build a temperature chamber and control the temperature. Materials and Methods: Materials 0 a. 1 Thermistor 1 b. 3 Resistors 2 c. 1 Potentiometer 3 d. Digital Multi-meter 4 e. K-Type Thermocouple 5 f. Box of Wires 6 g. 2 Cups (1 for hot water, 1 for cold water) h. Plastic Bag Part I: Building a Thermometer Using a Thermistor and Wheatstone Bridge Circuit First, a thermometer was built using the thermistor and the Wheatstone bridge circuit shown in Figure 1 below. The thermistor was used for R2 and the potentiometer for R4, which has three connections, with the third left unconnected. The difference between V2 and V1 was measured by connecting a wire from V2 to ACH5+ and V1 to ACH5-. Figure 1: Wheatstone bridge circuit 1
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To monitor the voltage difference through LabVIEW, the LabVIEW VI shown in Figure 2 below was built and saved as “”. Figure 2: Thermistor,vi LabVIEW program used in Part I The VI was implemented to balance the bridge circuit at room temperature by adjusting the potentiometer until the voltage difference was zero. Balancing the bridge simply means adjusting the resistor values until the voltage difference across V1-V2 equals zero. Next, “” was used to calibrate the thermistor. This
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This note was uploaded on 11/03/2009 for the course BMEN 305 taught by Professor Meissner during the Spring '07 term at Texas A&M.

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Lab 9 write-up - Introduction The purpose of this lab is to...

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