Bonnie Adams postlab 4 - Bonnie Adams BME 405 Postlab 4...

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Bonnie Adams BME 405 Postlab 4 Laboratory 4: Temperature measurements – Dynamic characteristics of first order systems – Virtual thermometer Introduction: The purpose of this lab was to learn how to use both the thermocouple and the thermistor, measure the dynamic characteristic of the first-order thermometer, and to design a vi that operates like a medical thermometer using the thermistor. Data: Hooking up the thermocouple and reading temperature: In this section, we used the thermocouple to read temperatures. On the BNC connector, the thermocouple was plugged in and the switch was moved to the right on the connector box BNC 2120 to enable that input. In LabVIEW, we opened a new vi and made a new DAQmx task called thermocouple output. The input was thermocouple ai1. The thermocouple type was K (which is written on the thermocouple connector), the CJC source was set to constant, and the CJC value was room temperature, which for this experiment was assumed to be 20 o C. We set the task to continuous acquisition mode, samples to read to 1000 and sampling rate to 200 Hz. On the front panel, we had a waveform graph indicator to display the output of the vi. We ran the vi and verified that the thermocouple worked by putting the tip of the thermocouple in different temperatures and comparing it with the temperature changes on the graph. The values returned were good (hand=28, room=21, ice=2). The relationship between the voltage and the temperature is Vref = c0 + c1*Tref + c2*Tref^2 + c3*Tref^3 + c4*Tref^4 + c5*Tref^5 + c6*Tref^6 + c7*Tref^7 + c8*Tref^8 + c9*Tref^9, where coefficients c0 through c9 are very small, between .039 and -1.2E-26. (Source: ) The convenience of using a thermocouple is that no complex circuit muct be built, and the thermocouple is standardized so the conversion is built in. However, there are sources of error
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