Detection range and accuracy specs.

Transcription

1 Example Detection range and accuracy specs. Calculate accuracy and relative error for I = ma in all possible ranges. Select the best range and answer why is the best? Write the display indication of each resolution.

2 Calculate accuracy and relative error for I = 4.03 ma in all possible ranges. Select the best range and answer why is the best? Write the display indication of each resolution. 76.5%

3 Example Sensitivity

4 Linearity / Non-linearity Estimate the sensitivity in the 0-100Pa range and calculate the non-linearity of the gas sensor response for a C2Cl4 partial pressure of 70 Pa.

5 Error of the mean Quality control of nine batches of milk produce have recorded the following concentrations of cholesterol in [mg/100ml] is Assuming a normal distribution of measured values: a) Calculate the mean value and standard deviation. b) Calculate the error of the mean

6 Indicate (shading the area) in the following figure the probability that corresponds to measure a concentration of cholesterol smaller than 7.30 mg/100ml milk.! Indicate (shading the area) in the following figure the probability that corresponds to measure a concentration of cholesterol larger than 7.42 and smaller than 7.60 mg/ 100ml milk.! -0.51!

7 In a milk production plant the cholesterol concentration in the milk production is expressed with a 90% confidence, and in the daily production 100 samples of 100ml are taken for quality control. a) If 9 batches show cholesterol concentrations 12 mg/100ml, is the production OK? b) If 11 batches show cholesterol concentrations 8 mg/100ml, is the production OK? c) If 24 batches have the value 7.8 mg/100ml, is the production OK? recalculated for 100 samples = samples samples must be within this range

8 Error propagation

9 Error propagation One parameter used for comparison of bioreactor performance is the power input (P/V) where the power numbers (Np) is a function of the Re number, d is the impeller diameter, [m] N is the agitation speed [rpm], ρ is the density [kg/m3] and V the working volume [m3]. Calculate the error in the P/V determination if: Np = 5 N = 10rpm ±1% d = 30 cm V = 0.5 m3 ± 3% ρ = 1000 kg/m3 ± 2%

10 Explain how to measure the internal resistance RA of the ammeter with the following circuit. Which parameters are fixed, and which are varied during the measurement? Which ratio between the total I and IRA is set?

11 The performance of 10 identical measuring instruments is monitored over a 320-days period. If a total of 5 faults are recorded in this period: a) Calculate the mean-time-between-failures (MTBF). b) If the mean time to repair (MTTR) is 7 days, calculate the availability. c) Calculate the probability that the instrument will fail in the first 100 days of use. d) Calculate the reliability R of the instrument for the first 100 days of use. e) If five identical instruments of reliability R (calculated in d) are connected according to the following figure, calculate the total reliability of the system. 7

12 Given the following voltage waveform calculate: a) Mean voltage (Um). b) Rectified mean voltage (Urm). c) Root mean squared voltage (Urms). d) Form factor. e) Top factor. f) Explain the physical meaning of the rms value U

13 ADC 0.745V Which type of ADC represents the circuit? Explain how it works?

14 calculated adding areas

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16 Write the Ru value in terms of Rv, R1 and R2 when VAB = 0 A Rv R1 R2 V Ru B Question If the nominal value of the resistor (Ru) representing a resistive sensor output is Ru = 110Ohm ±1.2%, and the strain gauge pressure sensor operates in the 0-20 Pa range, with R1 = 100Ohm± 1%; R2 = 100Ohm±0.5% and R3 = 110Ohm±0.4% Calculate the value of the voltage source (Vi) necessary to limit the current through the strain gauge to 15 ma. Calculate the bridge output (Vo) when a 12 Pa pressure is measured with a pressure sensor with a sensitivity of 0.2Ohm/Pa and the bridge is excited with Vi. R3 Vi Vo

17 A variable dielectric capacitive displacement sensor consists of two square metal plates of side 2.5 cm, separated by a gap of 1.3 mm. A sheet of dielectric material 1.3 mm thick and of the same area as the plates can be slid between them as shown in the figure. Given that the dielectric constant of air is 1 and that of the dielectric material 2.4, calculate the capacitance of the sensor when the input displacement x = 0.0, 1.7, 3 and 5 cm. ε0 = x F/m

18 Compensation wires and Law of intermediate materials m1 m1 m2 m2 T1 Tr with compensation wires E2 = E3 = 0 E1 = (Em2 - Em1)Th E5 = (ECu - Em2)Tr E4 = (Em1 - ECu)Tr (E1)Th = Em - (Em1 - ECu + ECu - Em2)Tr Cu Em Cu (E1)Th = Em - (Em1 - Em2)Tr -(Em1 - Em2)Tr = (Em2 - Em1)Tr Th Tr

19 Example Thermocouples Suppose that the reference junction of a chromel constantan thermocouple is maintained at a temperature of 80 C and the output e.m.f. measured is mv when the hot junction is immersed in a fluid. Which is the temperature of the fluid? Tfluid = 600 C

20 Suppose that the reference junction of a chromel constantan thermocouple is maintained at a temperature of 55 C and the output e.m.f. measured is mv when the hot junction is immersed in a fluid. Which is the temperature of the fluid?!

21 chromel constantan 40 C 0 C constantan chromel Suppose that the reference junction of a chromel constantan thermocouple is maintained at a temperature of 0 C and the output e.m.f. measured is mv when the hot junction is immersed in a fluid, but the instrument is connected to the thermocouple through extension wires and the connection is at 40 C. Which is the temperature of the fluid?!

22 An ultrasonic Doppler flowmeter is to be used to measure the volume flow rate of a slurry in a steel pipe of diameter 0.13 m. Two piezoelectric crystals, each having a natural frequency of 0.95 MHz, are positioned, a few millimetres apart, on the outside of the pipe to form an ultrasonic transmission link. The transmitting crystal directs an ultrasonic beam into the pipe so that the beam is moving in an opposite direction to the flow stream. The angle between the ultrasonic beam and the direction of flow is 57. On average 18% of the ultrasonic power reaching each solid particle is scattered back in the direction of the receiving crystal. Assume that the slurry has the same density and sound velocity as water (c 1.5x10 3 ms 1 ) and a power attenuation coefficient of 1.0 m 1. Find the difference between the frequencies of the transmitted and received beams when the flow rate is m 3 h 1.

23 20 C response Question