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FirstQuiz
341
| Question | Answer |
|---|---|
| Thermocouple | Two wires of different metals. Voltage gradient is produced due to a difference in temperature at two junctions allowing for one to create a correlation b/t voltage and temperature difference. Many types based on the alloys used. |
| Thermistor | Temp. sensor. Exhibits the largest resistance change w.r.t change in temp. |
| RTD | Temperature sensor PTC (resistance increases w/ temp. increase) Made of platinum, nickel, or copper Correlates resistance with to temperature Used infrequently |
| Cold Junction Compensation | A temperature sensor is placed next to the RJ. Add this to the gradient picked up by the thermocouple, and an abosolute temperature at the measurement junction can be found. |
| Thermocouple "types" | Refer to the different standardized alloy pairs of thermocouple wires (alloy pairs because, remember, we have two wires connected at a common junction). The different alloying pairs allow for different functionalities amongst the thermoucples. |
| PTC thermistors vs. NTC thermistors | PTC-resistance increases with increasing temperature. NTC- resistance decreases with increasing temperature |
| Measurement | A comparison b/t a standard and what we want to measure (the measured). |
| Standard | Something considered by an authority as a basis of comparison. Other parameters can be defined in terms of these standard parameters (velocity=length/time, where length and time already have established parameters). |
| Sensor | Uses a natural phenomenon to sense the variable being measured (thermometers, thermocouples, etc.). It measures this variable (often a physical quantity) and converts it into a signal which can be read by an observer or an instrument. |
| Transducer | Converts the sensed information into a detectable signal |
| Signal Conditioning | Modifies (amplification, filtering) the signal for the final stage. |
| Independent Variables | A variable that can be changed independent of other variables. They do not affect its value. |
| Dependent Variables | A variable that IS affected by a change in other variables. |
| Analog/Digital | Analog- Varies Smoothly, continuous (glass thermometer) Digital- Varies in a step-wise manner Example: Thermometer with a digital display. |
| Static Signal | Constant with respect to time, easily read with analog display. -Glass thermometer -Tire Gages |
| Dynamic Signal | Varies w.r.t. time. Typically read with a measuring system with recording capabilities. |
| Noise/interference | Noise- Random variation in output due to of extraneous factors such as environment or temperature. Static from radio. Interference- Produces unwanted deterministic trends from extraneous variables. |
| Hysteresis | When a graph does not act the same on the way up as it does on the way down. Difference b/t the upscale and the downscale. |
| Repetitions vs. Replication | Repetition- Repeated measurements made during any single test or on a single batch. Replication- An independent duplication of a set of measurements using similar operating conditions. |
| Test Matrix | A way of ensuring that all the various test possibilities were obtained. |
| Range | The difference between the highest and lowest values in the set. |
| Sensitivity | The change in the output per unit change in the input. Determines the useful range. In the case of a linear calibration curve the slope of the line is called the static sensitivity |
| Accuracy | The closeness of a measurement (or a set of observations) to the true value. |
| Precision | The closeness of multiple observations or repeatability of a measurement. Refers to how close a set of measurements are to each other. It can often tell you if your experimental set-up produces repeatable results. |
| Calibration | A measurement of performance of an instrument or sensor to ensure accuracy for future measurements. Done by applying a known value of input to a measurement system, and then observing the systems output. |
| Hysteresis Error | Errors that are produced due to the fact that hysteresis is present |
| Linearity Error | Deviations from linear behavior. This can be calculated. |
| Zero Shift (null) Error | Variation in the linearity parameter a0. Sensitive to temperature fluctuations. |
| (Instrument) Repeatability | The measure of the variation that occurs when a sensor is repeatedly calibrated under identical conditions. This is normally described by the Standard Deviation, Sx, of the data |
| Sensitivity Error | Variation in the linearity parameter a1. Sensitive to temperature fluctuations. |
| *Calibration Curve | Obtained by plotting the output vs. the input. This also determines the useful range within which the instrument/sensor/system can be used. |
| *Resolution (of a sensor) | The minimum detectable signal fluctuation. |
| *Absolute Error | =true-indicated value |
| *%Accuracy | (1-(abs[absolute error]/true)*100 |
| *Uncertainty | A likely bound on the error or a part or measurement. Uncertainty is dictated by application. |
| *Precision Error | A measure of the random variation found during repeated measurements. |
| Bias Error | The difference between the average and true values |
| *Linearity | yl(x)=a0+a1x -> Many types of sensors have linear input/output behavior, at least in some range. That region follows the equation above. The only calibration you will often get are: a1- the slope of the input/output relation a0- the zero input value |
| Variable | The basic quantity being measured |
| *Control of a variable | Holding a variable to a prescribed value during an experiment. |
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NoodlesNoodles
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