Data Acquisition Flashcards

Question

``` The equation illustrates the relationship between the Gain in decibels and the gain of an amplifier. Which of the following answers (a-d) correctly represents the gain in dB if a voltage of 100μV is the input to the amplifier and a voltage of 5V is measured as the output. The answers are displayed in 2 decimal places format. (A single answer is correct). GdB = 20 Log(G) a. -93.98 dB b. 93.98 dB c. 33.98 dB d. -33.98 dB ```

Answer 1

b. 93.98 dB ``` 100μV = 0.1mV = 0.0001V 20 log(5/0.0001) = 93.98dB ```

Answer 2

a. 100Hz Loop executes every 10ms. 10ms occurs 100x in 1s. Hence, 100Hz.

Answer 3

d. 0.15mV 10 / 2^16 = 0.15mV

Answer 4

All are correct. Says only a and d, but b and c are defo right also.

Answer 5

a. Many samples are acquired at a faster rate than can be displayed b. The sampling rate must be precise Use buffered I/O when: 1. Many samples are acquired at a rate faster than is practical to display, store, or analyze in real-time 2. Data is acquired/displayed continuously on the fly 3. The sampling period must be precise and uniform throughout the data samples

Answer 6

b. The accuracy of the sensor is the maximum difference that will exist between the actual value and the indicated value at the output of the sensor. c. The resolution of a system is the smallest increment it can measure ``` Resolution = x dp Accuracy = +- x ```

Answer 7

b. A situation where the timing of events or the scheduling of tasks may unintentionally affect an output or data value. The definition^

Answer 8

d. Cannot say We don't know as there is no initial value at the shift register

Answer 9

a. Sequence structures are not an efficient way to program if we may need to change the order in which the sequences are to execute. b. The sequence frames will execute Left to Right. You cannot stop part way through and you can pass data between frames

Answer 10

b. Indicator 1 will count upwards in increments of 0.1 starting at 0. d. This code illustrates how you can program in parallel with LabVIEW. a. Is obviously wrong. c. Is wrong because CONTINUE IF TRUE SYMBOL. Hence false constant means that the bottom loop will run only once and output 0.

Answer 11

b. Analogue Output, Analogue Input, Digital I/O, Counters Duplicate with card 1.

Answer 12

a. Fibre optic strain gauges are a good choice when there are high levels of background electro-magnetic interference. b. Three important factors when choosing a sensor are environmental factors, economic factors and sensor characteristics. c. A single channel optical encoder with 200 gratings will have a resolution of 1.8deg. Fibre optic gauges are immune to EM, yes, 360deg/200 = 1.8deg, encoder always outputs digital.

Answer 13

a. The top loop will execute 2 times. d. Indicator and Indicator 2 will display the same value when the programme finishes executing. Not parallel as they're connected, hence it flows. Also the 1st loop will stop before the 2nd as not parallel. Imagine it was electrical, it would be series as wire connecting.

Answer 14

a. The loop will execute 5 times. So essentially every value gets inserted but then deleted as NO shift register. So every value gets overwritten outside the loop and the output array will be identical to the input array. Technically, the 5th/last value would have been inserted into the array but its 5th element in a 3 element array hence ignored. a. Yes iterates 5 times. b. Wrong because no shift register c. No its a 3 element array. d. No. The code won't write any values as explained above.

Answer 15

a. The 6 bit binary number 000011 represents the decimal number 3. c. Sensors which utilize digital signals as outputs are less susceptible to low voltage noise induced in the transmission wiring. d. Multiplexers can be utilized in DAQ systems to reduce the cost. a. 0... + 1*2^1 + 1*2^0 = 2+1 = 3 b. 2^6 -1 = 63 not 64 c. 1's and 0's vs physical analogue? So digital signals are far more immune to interference. d. Multiplexing involves routing a number of signals into a single digitizer. This is a much more cost effective way of expanding the signal count of the system. Multiplexing is necessary for any high channel count application.

Answer 16

b. 9 1+2+1+1=5 5+2+1+1=9 Key is that the shift registers are baso trickle down. So top gets 5, mid[1], bottom[2]. Hence, mid and bottom both stay on the initial value of 1.

Answer 17

b. When the loop has completed the iteration terminal will have a value of 2 associated with it. c. Given the input to the or gate, it serves little function and could be removed without effecting the codes functionality. This is a while loop. not a for loop. A for loop is like a pad of paper with a corner folded over. 0>1 false, 1>1 false, 2>1 true so stop. 3 iterations so value shows 2 (indexed). And yes the or gate is pointless and makes no sense.

Answer 18

a. A While Loop must execute at least once c. You can have a While Loop within a While Loop. d. A While Loop iteration terminal is zero indexed Both can have stop buttons, i.e. conditional terminals.

Answer 19

b. You can have an array with more than 5 dimensions. c. You can have a cluster with multiple data types within it Bool, string, numerical in clusters...but not arrays. Think a cluster of data types.

Answer 20

b. 0.596μV 10V / 2^24 = 0.596μV

Answer 21

a. The loop will execute 20 times b. ‘Waveform Graph’ will display 20 random numbers c. ‘Waveform Graph’ will only display data after the loop has finished d. The figure illustrates a For Loop All are correct. Waveform graph is outside the loop and has auto indexing tunnel. Hence, it will plot once the loop has finished and sends the data outside the loop. A for loop is the pad of paper with a corner folded.

Answer 22

b. Buffered Data Acquisition requires a fixed sample rate. c. A control system will be unreliable using a Buffered Data Acquisition approach. d. Timing functions provide the processor with time to complete other tasks Hysteresis is dependent on its previous state. Buffered Data Acquisition needs a fixed sample rate and isn't suitable for control applications. Timing functions do allow time. Think...while waiting it will still do other tasks in the code elsewhere if running parallel.

Answer 23

a. A multiplexer is used to route a number of signals into a single digitiser b. In general, a sensor with a digital output will be less susceptible to noise than a sensor with an analogue output c. Sensors utilizing modulated infrared signals can detect a signal even if the strength is low. d. Intensity based infrared sensors are susceptible to problems caused by ambient light levels All are correct.

Answer 24

a. 17m Sound travels at 340m/s. Hence, 100ms = 0.1s x 340m/s = 34m 34m and 100ms is round trip there and back. Hence, /2 = 17m

Answer 25

d. 32 1x2=2, 2x2=4, 4x2=8, 8x2=16, 16x2=32 Baso, 2^5 = 32

Answer 26

a. Hysteresis means the output will be dependent on its recent previous states ^^^Definition

Answer 27

d. 12 Not initialized shift register, therefore uses 0 or last value. Ran twice doesn't mean iterations! 1st Run 2nd Run 0+3=3 6+3=9 3+3=6 9+3=12

Answer 28

c. ‘Iterations’ will display a value of 4 when the for loop completes. d. Data will only leave the For Loop once it has executed. 5 element array, hence 5 iterations, which will be displayed as 4.

Answer 29

b. Aliasing is caused by a sampling rate which is too low for the frequencies being measured c. The Nyquist theorem states that when an analogue signal is sampled any signal components at frequencies greater than one-half the sampling frequency appear in the sampled data as a lower frequency signal d. Aliasing can be avoided by removing signal components above one half of the sampling frequency Aliasing arises when a signal is UNDER sampled

Answer 30

d. The accuracy of an input/output card is dependent on the bit length e.g. 12bit, 16bit I think the most common is like 12 bit. A deterministic system is a system in which no randomness is involved in the development of future states of the system, so windows systems can be random basically. Can be both analogue and digital. Yes accuracy is related to the bit length.

Answer 31

a. Fibre optic strain gauges are immune to electro-magnetic noise. c. Quadrature rotary encoders can be used to determine the direction of rotation. d. Choosing a sensor involves consideration of environmental, economic, and sensor characteristics. Modulated IR sensors are less susceptible to external interference. Quadrature rotary encoders can be used as they have 2 channels (2 sensors and 2 receivers).

Answer 32

a. Filters can be utilized to remove both high frequency and low frequency signals b. Stopband ripple is undesirable c. An ideal filter will have a sharp transition d. Passband ripple is undesirable High-pass can remove lows, and low-pass can remove highs. Think high-pass = let the highs pass through. Ripples are undesirable and caused by poorly designed filters. An ideal filter will have a flat response where the desired signal is not altered. Then a sharp transition to reduce unwanted frequencies.

Answer 33

c. When a measurement system is calibrated there is zero bias error No accuracy is +- x, so not absolute. Random errors can be different sizes every time they occur. Imperfect calibration is a cause of bias error, hence calibrate means no bias error. +ve and -ve ranges can be different sizes.

Answer 34

a. ‘indicator’ will display the time taken for the last loop to execute. c. If ‘Stop Button’ has a value of false the loop will continue. d. Each time the loop executes the value in the left hand side shift register terminal will be the value that was sent to the right hand side shift register terminal in the previous loop iteration Will show the time taken for the most recent loop, not necessarily 50ms as it still has to execute after that, so more likely 50ms + a few ms. Its an infinite loop until stop=true as there are no set number of iterations. Yes that is how shift registers work.

Answer 35

d. In total 100 random numbers will be generated within the loop Pad of paper with a corner folded is a for loop. Coercion dots are used when LabVIEW has converted data/values into a different representation. That symbol means wait until next multiple, so the loop will run every multiple of 1000ms. So its baso the same unless the loop starts at a weird time, so 57ms into the code if that makes sense.

Answer 36

b. Once the .vi begins Loop 2 will execute only once c. The loops are programmed to execute at different frequencies d. The first data point on ‘Chart 1’ will have a magnitude of zero a and b. If the loop control is pressed and true. It will stop loop 1, be outputted and enter loop 2. Loop 2 will execute just once and then stop. c. Yes as iterations constantly increasing d. Yes as sin(0) = 0

Answer 37

b. The For loop will run 2 times. The output of indicator ‘iteration terminal output’ will be 0, 1.

Answer 38

``` Pink = String Orange = Numeric Green = Boolean ```

Answer 39

a. The While loop will run 3 times. The highest value the iteration terminal will indicate is 2.

Answer 40

The stop button is the condition terminal. I.e. it is dependent on a condition.

Answer 41

2^8 = 256 values. Not 255, that is the highest number possible as 0 included.

Answer 42

b. While loops must execute at least once c. While loops have a conditional terminal d. While loops can theoretically run infinitely While loops must execute more than once, and can run for as long as the while is true.

Answer 43

a. For loops can execute zero times c. For loops can have a conditional terminal For loops have to have a set number of iteration given outside the loop, however if condition is met they can stop early.

Answer 44

a. Buffered Data Acquisition requires a fixed sample rate.

Answer 45

c. The output of ‘indicator’ when the loop finishes will be 8.

Answer 46

a. DAQ systems with an FPGA can achieve superior performance. c. DAQ systems with an FPGA are more deterministic.

Answer 47

a. A wait function inside a loop allows the .vi to sleep for a set amount of time. b. Timing functions control the frequency that a loop executes. c. Timing functions provide the processor with time to complete other tasks Timing functions can be used in case structures hence false. But they can cause problems and hence should be avoided.

Answer 48

c. Represents Accuracy without Precision.

Answer 49

a. Hysteresis means that the change in a parameter is dependent on its previous state. c. A DAQ system with a low level of Hysteresis is desirable.

Answer 50

All correct.

Answer 51

b. ADC’s are needed for DAQ systems that utilise Personal Computers. d. ADC’s are optimised for either resolution or sampling rate.

Answer 52

a. The indicator will display a value of 4.5 when the loop finishes executing. d. The loop will execute two times.

Answer 53

a. Sequence structures are not an efficient way to program if we may need to change the order in which the sequences are to execute. c. You cannot stop a sequence structure part way through its execution. d. The sequence frames will execute left to right.

Answer 54

a. Clusters can contain an Array of Boolean values.

Answer 55

d. Unbundle by name enables an easier interpretation of the data within the cluster as each cluster element has an associated name.

Answer 56

b. You can have an array with more than 3 dimensions. c. It is possible to have a 2D array of ‘string’ data type. d. The first element in an array is indexed at 0.

Answer 57

a. Arrays do not have to be a fixed size b. You cannot have an array of arrays d. Clusters can contain more than one data type A cluster can contain boolean, string and numeric.

Answer 58

c. Use a modulator and demodulator

Answer 59

a. Stop electrocution b. Reduces problems due to improper grounding c. Protects sensitive measurement equipment

Answer 60

a. Power consumption b. Lifetime c. Economic factors d. Linearity

Answer 61

b. Amplify the sensor output with a gain of 2 | d. Use a higher bit system to improve the resolution

Answer 62

c. 0.625V 10V / 2^4 =0.625V

Answer 63

c. The VI contains a For Loop which has the optional Condition Stop terminal enabled. So e.g. can be used to stop the loop on an error

Answer 64

Total Error = Bias Error + Random Error Bias Error = True Value vs True Average Random Error = True Average vs Measured Value

Answer 65

Temperature Vibration Acoustic noise level Humidity

Answer 66

When data is transferred between the DAQ and computer memory directly. I.e. circumventing the CPU.

Answer 67

IRQ transfers rely on the CPU. So more computationally heavy.

Answer 68

A deterministic system is a system where no randomness is involved in the development of future states of the system.

Answer 69

1. Many samples that are acquired at a rate faster than is practical to display, store or analyse. 2. Data is acquired/displayed continuously on the fly. 3. The sampling period must be precise. 4. If the LabVIEW vi specifies it uses buffered, not nonbuffered,

Answer 70

1. The data set is small and short. 2. To reduce memory overhead, as buffered takes up extra memory. 3. If the LabVIEW vi specifies it uses nonbuffered, not buffered,

Answer 71

It is uninitialised as has no default values.

Answer 72

The top one does not auto-index. | The bottom one does auto-index. I.e. iteration 1 = column

Answer 73

Left is the state functionality code. | Right is the transition code.

Answer 74

To convert energy from one type such as temperature, strain pressure or light into another. Essentially, physical quantities to electrical quantities such as voltage or resistance.

Answer 75

Playing a guitar through a sound system. Low voltage signal out could pick up noise when in the cables, so we pre-amplify it before sending it out.

Answer 76

Foil strain is the cheapest and most common. Fibre optic is the compact but most expensive. Piezoelectric strain sensor is the very high resolution.

Answer 77

IR light source is flashed at a specific frequency. The detector also runs at the same frequency (matches it). The benefit of this is that flashes and hence information can be detected despite external interference such as ambient light and reflections. This is used in IR remotes and proximity sensors.

Answer 78

The loops do not stop since the loop control is outside the while loops. Press run, false loop control is inputted into the loops. The loops continue to run. Loop control is pressed and now true is waiting to go into the loop. But it can only enter the loop once the loop stops.

Answer 79

With the loop control inside the while loop. Loop 1 will stop when = true. This true value will then be sent out of loop 1 to loop 2. Loop 2 will run once, and then stop.

Answer 80

It is an integrated circuit that can be programmed to deterministically perform a task. They can help to achieve superior performance.

Answer 81

A red dot that is highlighted by labVIEW if you use data that is different but labVIEW can convert it for you as similar. E.g. orange and blue added together

Answer 82

``` Linear / Non-linear Time-invariant / Time-variant Analog / Digital Discrete / Continuous time Passive / Active ```

Answer 83

This is a low pass filter. 25 dB to -15 dB. Hence, 25 + 15 = 40dB

Answer 84

This is a high pass filter. 1kHz signal with 60Hz noise at 40dB. We can apply a 60dB signal at 60Hz to ensure the signal level is 20dB above the interference

Answer 85

Desired: 1. A flat response (desired signal isn't altered). 2. Sharp transition (to prevent interference). Undesired: 1. Passband ripple where the frequencies we want are distorted. 2. Slow transition. 3. Stopband ripple where the frequencies we don't want are distorted and hence can appear.

Answer 86

This is bandpass filter.

Answer 87

They are a common filter designed to have as flat a frequency as possible in the pass band. I.e. the most accurate desired signal. Characteristics: Smooth response at all frequencies. A perfect pass band and stop bands. So pass band completely flat, and stop band pinned to 0. Butterworth are often classed by their order. Think higher order polynomial = more responsive. So rapid cut off.