Lesson 3 Flashcards
(33 cards)
What are sensors in the context of measurement chains?
Sensors are the first components of a measurement chain that convert physical and chemical variables into electrical signals.
Sensors typically begin as analogical signals and must accurately reflect the involved variables.
What is the role of calibration in sensor measurement?
Calibration establishes the relationship between the electrical signal and the measurand through the calibration curve.
This involves using standard units of measurement to derive the function F(m).
Define ‘measurand’ in the context of sensors.
The quantity to be measured, denoted as ‘m’.
What is the expression that relates the sensor output ‘s’ to the measurand ‘m’?
s = F(m), where F(m) is established by calibration.
What is sensitivity in the context of sensors?
Sensitivity (S) is defined as the derivative dA/dm = F(m).
What condition must a sensor meet to have constant sensitivity?
The sensor must be linear.
What are passive sensors and how do they function?
Passive sensors are sensors that require an electrical energy source to read the signal ‘s’ and are part of a measurement chain.
They generally cannot be used directly.
What is a measurement chain?
A range of circuits or devices that amplify, adapt, and convert signals from sensors.
What are influence variables in sensor measurements?
Influence variables are physical variables in the environment, such as temperature or humidity, that can affect sensor performance.
What are the two types of uncertainties in measurement?
Systematic errors and random uncertainties.
True or False: Random errors can be completely avoided in measurements.
False.
What methods can reduce random uncertainties in measurements?
Protection methods such as electrical regulation, temperature stabilization, mechanical isolation, and electromagnetic shields can reduce random uncertainties.
What is the statistical approach to analyzing random errors?
Random errors become part of statistics and are labeled as uncertainties.
What is the mean value in the context of multiple measurements?
The mean value (S) is the average of all measurements taken of the same measurand.
How is variance calculated in measurement analysis?
Variance (v) is calculated based on the differences between measured values and the mean value.
Fill in the blank: The standard deviation is denoted by _______.
o
What does the calibration curve help deduce?
It helps deduce the value of the unknown measurand ‘m’ based on the electrical signal ‘s’.
What is the relationship between response time and band pass in sensors?
Response time and band pass are closely related; the sensor’s sensitivity depends on the frequency of the input signal.
What can long-term drifts in sensors cause?
They can nullify the function F(m).
What is the primary goal of error reduction methods in measurements?
To achieve the closest probable value of the measurand.
What is defined as ‘the value of a measurand obtained by measurement’?
The result of the measurement
This is the uncorrected result or the result of a measurement before correction for assumed systematic errors.
What are the two main approaches to error reduction?
- Experimental solutions
- Statistical solutions
Experimental solutions involve physical methods like impedance matching and noise reduction, while statistical solutions involve mathematical analyses after measurements.
What is an uncorrected result?
The result of a measurement before correction for assumed systematic errors
This is essential to obtain the corrected result.
What is a corrected result?
The result of a measurement obtained after corrections have been made to the uncorrected result
Corrections account for assumed systematic errors.
