Lab 1 Flashcards
everything from lab 1 that i might need to know: includes lecture slides, prelab, lab and quiz questions if i remember them
Thermocouple
2 wire legs from different metals
welded together to make a junction - this is where the voltage is measured
Typical accuracy: 1−2 °C
RTD - resistance temperature device
wire and thin film devices that exhibit temperature sensitive electrical resistance - resistance is linear
Typical accuracy: 0.15−4.6 °C
thermistor
semiconducting
resistances decrease rapidly with increasing temperature
Typical accuracy: 0.1°C to 0.2°C
limited thermistors to high-resolution measurements over limited ranges.
measuring rtd resistance
connect rtd to multimeter to measure resistance
need lead wire resistance bc Rreading = Rleadwire + Rrtd/thermistor
seeback effect
electric current will flow continuously i na closed circuit made up of two dissimilar metals if the junctions of the materials were maintained at two different temperatures
Vh=Vc=S(Tc-Th)
law of intermediate metals
insertion of an intermediate metal into a thermocouple circuit will not affect the thermoelectric coltage output so long as the two junctions are at the same temperature and the material is homogenous
law of intermediate temperatures
is a thermocoupel circuit develops a net thermoelectric voltage v2-1 for measuring junction temperatures T2 and T1 and a net v3-2 for temperatures T3 and T2 then it will develop a net voltage of v3-1 = v2-1 + v3-2 when the junction temperatures are at T3 and T1
Accuracy
refers to how closely a measured or average value agrees with the
true value.
Precision
refers to how closely individual measurements agree with each other
instrument resolution
smallest change that can be measured on teh instrument being used
digital displays - value of the least significant digit
analog - smallest detectable reasing
determined by instrument noise and the smallest detectable change on the display of an instrument
measurement (instrument) sensitivity
slope of the output characteristic curve for an instrument
change in output/input that creates the output change
