• Author / Uploaded
• Ianne Mary Torino

• Categories
• Exactitud y precisión
• Presión
• Observación científica
• Cantidades fisicas
• Física y matemáticas

Citation preview

TORINO, IANNE MARY C. EE1

1.1What is the difference between controlled and manipulated variables? Controlled variables are the variables measured to indicate the condition of the process output while manipulated variables are variables controlled by an actuator to correct for changes in the measured variable. 1.2What is the difference between set point, error signal, and correction signal? Set point is the reference value for a controlled variable in a process control loop; Error signal is the difference in value between a measured signal and a set point; Correction signal is the signal to the manipulated variable. 1.3How many pounds are equivalent to 63 kg? 63kg (1kg/2.205lbs) = 138.925 lbs 1.4How many micrometers are equivalent to 0.73 milli-in? 0.73 x 10-3 in (25400 μm/1in) = 18.542 μm 1.5 How many pounds per square inch are equivalent to 38.2 kPa? 38.2 kPa (14.7 psi/101.325 kPa) = 5.54 psi 1.6 How many foot-pounds of energy are equivalent to 195 J? 195 J ( 0.7376 foot-pound/1 J) = 143.82 foot pounds 1.7 What force in pounds is equivalent to 385 N? 385 N (.225 lbs/ 1 N) = 86.625 lbs 1.8 How many amperes are required from a 110-V supply to generate 1.2 hp? Assume 93- percent efficiency. 1.2 hp ( 746 W/ 1 hp) = 895.2 W Input power = 895.2 W /.93 = 962.5806 W Current = 962.5806 W / 110 V = 8.7507 A 1.9 How many joules are equivalent to 27 ft⋅lb of energy? 27 ft⋅lb ( 1 J/ 0.7376 ft⋅lb) = 36.61 J 1.10 What is the sensitivity of an instrument whose output is 17.5 mV for an input change of 7°C? Sensitivity = 17.5 mV/ 7°C = 2.5 mV/7°C

1.11 A temperature sensor has a range of 0 to 120°C and an absolute accuracy of ±3°C. What is its FSD percent accuracy? % FSD accuracy = ± (3 × 100/120) % = ± 2.5 % 1.12 A flow sensor has a range of 0 to 25 m/s and a FSD accuracy of ±4.5 percent. What is the absolute accuracy? Absolute accuracy = ± ( 25 × 4.5/100) % = ± 1.125 % 1.13 Introduction and Review 131.13 A pressure sensor has a range of 30 to 125 kPa and the absolute accuracy is ±2 kPa. What is its percent full-scale and span accuracy? % FSD accuracy = ± (2 × 100/125) % = ± 1.6 % % Span accuracy =± (2 × 100/95) % = ± 2.1 % 1.14 A temperature instrument has a range −20°F to 500°F. What is the error at 220°F? Assume the accuracy is (a) ±7 percent of FSD and (b) ±7 percent of span. (a) (b) 1.15 A spring balance has a span of 10 to 120 kg and the absolute accuracy is ±3 kg. What is its %FSD accuracy and span accuracy? % FSD accuracy = ± (3 × 100/120) kg = ± 2.5 kg % % Span accuracy = ± (3 × 100/110) kg = ± 2.7 kg % 1.16 A digital thermometer with a temperate range of 129.9°C has an accuracy specification of ±1/2 of the least significant bit. What is its absolute accuracy, %FSD accuracy, and its resolution? Absolute accuracy = ± % FSD accuracy = ± % Span accuracy = ± 1.17 A flow instrument has an accuracy of (a) ±0.5 percent of reading and (b) 0.5%FSD. If the range of the instrument is 10 to 100 fps, what is the absolute accuracy at 45 fps? (a) Absolute accuracy = ± (45 × 0.5/100) fps = ± 2.25 fps (b) Absolute accuracy = ± (100 × 0.5/100) fps = ± 0.5 fps 1.18 A pressure gauge has a span of 50 to 150 psi and its absolute accuracy is ±5 psi. What is its %FSD and span accuracy? % FSD accuracy = ± (5 × 100/150) psi = ± 3.33 kg % % Span accuracy = ± (3 × 100/100) psi = ± 3 kg %

1.19 Plot a graph of the following readings for a pressure sensor to determine if there is hysteresis, and if so, what is the hysteresis as a percentage of FSD? True pressure (kPa) 0 20 40 60 80 100 80 60 40 20 0 Gauge pressure (kPa) 0 15 32 49.5 69 92 87 62 44 24 3 Hysteresis = ± 7 % FSD (see Fig. A1.1) 1.20 Plot a graph of the following readings for a temperature sensor to determine the linearity of the sensor. What is the nonlinearity as a percentage of FSD? True pressure (kPa) 0 20 40 60 80 100 Gauge reading (kPa) 0 16 34 56 82 110