Lab Excerpts

This experiment measured the pressure inside of a vessel (soda can). Strain values obtained from a P-3 strain measuring device attached to a strain gauge with a hoop or long orientation were used to calculate pressure values. Such information is applicable in making material decisions for consumer products and ensuring the safety of products that contain a pressure vessel.

Strain values from a P-3 strain measurement device varied from -122 με to -1954 με and were used to calculate strain values that varied from -8.35 psi to -48.9 psi. Application of Chauvenet’s Criterion did not result in the elimination of any data from the set, for which the mean and standard deviation were found to be -57.5 psi and 30.2 psi respectively.

Uncertainty in data was found to be fairly large with the lowest value being 11.1% and the highest being 25.1% from the results of a Kline and McClintock Uncertainty Analysis. Attribution of possible effects of differences in experimental values observed was found to be attributed to gage orientation among other variables such as vessel properties and contained liquid type.

This experiment explored method comparison through the use of various practices to measure the nominal speed of a flywheel (in RPM) for different applied voltages. Three data collection methods were used, and the data collected was compared and analyzed considering possible sources of error and uncertainties associated with each method. Method comparison is applicable in experimentation/lab work and the variable being measured is relevant in robotics, manufacturing systems, and consumer products.

An encoder (a NI myRIO with the LabVIEW VI), a handheld tachometer, and a stroboscope were used to obtain comparative data measurements for different voltages. The sweep of voltages was from 1.5 volts to 6.0 volts (in increments of 0.5 volts). A piece of reflective tape was applied to the flywheel for use in taking measurements with the tachometer and stroboscope. Values were found to range from 0 RPM to 980 RPM for the encoder, 195 RPM to 967 RPM for the tachometer, and 187 RPM to 956 RPM for the stroboscope (though, as noted in the experimental data section, the “0” encoder values were due to the voltage being too low for the RPM data to be picked up using this method). RPM data was observed to increase by a similar amount for each incremental (0.5 V) voltage increase among the data from all three methods.

The results of the analysis showed similarity in the data collected for respective voltages using each of the three methods, with some differentiation attributed to uncertainties related to the respective measurement methods and the devices incorporated.

This experiment explored method comparison through the use of various practices to obtain temperature measurements of an adjustable AC light fixture (in °C) over time. Three methods were used for data collection and analyzed with respect to possible sources of error and uncertainty. The comparison of experimental methods of data collection is applicable in lab work and industry and the variable measured (temperature) is relevant in various applications including but not limited to heating systems, lighting fixtures, and consumer products.

An IR camera, a thermistor (in a circuit with a myRIO and used in conjunction with a computer program), and a Type T thermocouple were used to obtain raw measurements over time for use in a comparative (temperature) analysis. Data were collected each minute for twenty minutes with the first measurement being taken one minute after turning on the light. Raw voltage data taken from the thermocouple (ranging from 0.699 mV to 1.486 mV) was converted to temperature values varying from 18°C to 37°C using a Type T thermocouple conversion chart (with a 0°C reference temperature). Raw resistance data taken from the thermistor (ranging from 10.4 kΩ to 3.21 kΩ) was converted to temperature values varying from 24.1°C to 53.1°C using the Steinhart-Hart Equation for temperature conversion with parameters corresponding to the thermistor used (10 kΩ). Temperature data from the IR camera varied from 25.8°C to 57.3°C.

Experimental values and corresponding temperatures were found to increase by a similar amount between each minute indicating a roughly linear, positive trend between light fixture temperature (at maximum brightness) and time and increase amounts were found to be slightly larger at the beginning of data collection (these trends were apparent in all three data sets). The resulting analysis of collected data indicated similar temperature values between thermistor and IR camera measurements (with percent differences ranging from 1.4% to 12% between the two. Temperature data obtained from the thermocouple was notably lower than that obtained from the other methods resulting in higher percent differences (with those between IR camera and thermocouple data ranging from 40% to 60% and those between thermocouple and thermistor data ranging from 30% to 50%). Error related to conversion uncertainty, junction contact with the light fixture, and use of a reference temperature (that may not have been exact) possibly contributed to differences observed. For this reason and also considering the uncertainty related to the conversion of thermistor resistance data, temperature measurement using an IR camera was established as the most accurate of the methods compared. Repeated trials were recommended to verify conclusions noted.