©
2012 Technological Studies
Standard Grade – Credit
Finalised Marking Instructions
 Scottish Qualifications Authority 2012
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These Marking Instructions have been prepared by Examination Teams for use by SQA
Appointed Markers when marking External Course Assessments. This publication must not
be reproduced for commercial or trade purposes.
Mark Allocation
1.
(a)
Marks
KU RNA
The system moves the camera to the position set by the user
 RNA
The error detector compares the desired position with the actual
position
 RNA
The O/P driver provides the power required to drive the motor
 RNA
The position sensor provides feedback
 RNA
2
1
0
(max 2)
plus any other valid point. Not “control right = moves right”
Closed loop has feedback
Open loop has no feedback
2.
Init:
Action:
 KU
 KU
2
1
0
let dirs = %1100000
Alternative:
symbol counter = b0
if pin 0 = 1 then jump
if pin 0 = 0 then action
goto action
high 7
jump:
 RNA
 RNA
 RNA
pause 1000
low 7
 RNA
for counter = 1 to 3
high 6
 RNA
 RNA
pause 200
7
6
5
4
3
2
1
0
low 6
pause 200
 RNA
 RNA
next counter
return
Page 2
Marks
KU RNA
3
(a)
Z=
 RNA for ANDing inputs
 RNA for OR conditions
A•B•C + A•B•C
(A•C  RNA)
2
1
0
(b)
Z = (A•C) + B
A
Z
B
C
1
0
 KU for 3 symbols
 RNA for connections to each gate
 KU
Quad 2 input AND
 KU
2
1
0
 RNA for each valid response
2
1
0
Hex Inverter
(d) High power consumption/high speed switching/unaffected by
static/low fan out
Page 3
3
2
1
0
Marks
KU RNA
4.
A
(a)
C
 KU for SPST symbol
 KU for buzzer symbol
B
6V
 RNA for connecting components in series to parallel
 RNA for connecting parallel switches
2
1
0
(b)
 KU
(c)
A resistor should be connected
 RNA
in series
 RNA
Page 4
1
0
2
1
0
2
1
0
Marks
KU RNA
5.
(a)
1
0
 KU
It is predictable/negative aesthetics of wind power
 RNA
(b) Wind causes a turbine to turn
 RNA
Turbine causes a generator to turn and produce electricity
(c)
2
1
0
Pollution/limited supply
 RNA for each valid descriptive response
(d)
(i)
E
=
MC ∆ T
7000 000
=
100 x 4190 x ∆ T
∆T
=
16·7°C
Final Temp
=
10 + 16·7 = 26·7°C
(27°C)
η
Eout
Ein
2
1
0
 RNA for substitution
 RNA for answer from
 RNA working(FTE)
3
2
1
0
(ii)
=
 RNA for substitution
=
7 MJ
=
11MJ
=
0·636
64%
 RNA for answer
from working
Page 5
2
1
0
Marks
KU RNA
6.
(a)
 KU for each valid
2
1
explanation/answer
0
Easier to reprogram/requires fewer components/
shorter assembly time/etc
Smaller/cheaper must be qualified
(b) Sub-system
Clock
Function
Synchronises the system/keeps all parts working
in time with each other
 KU
 KU
I/0 Port
Links the microcontroller to the outside world
 KU
EEPROM
Stores the program
ALU
Performs calculations
4
3
2
1
0
 KU
(c)
Electrically (Electronically), Eraseable, Programmable, Read-Only
 KU
Memory
(d) Reduce overall program size/make program easier to
understand/reduces memory requirement
 KU for each valid explanation/response
1
0
2
1
0
Microcontrollers use binary numbers in their calculations and operations.
(e)
(f)
(i)
56 = %
00111000
(ii)
%11001101 =
205
 RNA
1
0
 RNA
1
0
 KU
PWM/Pulse Width Modulation
Page 6
1
0
Marks
KU RNA
7.
(a)
Mechanism A
Mechanism B
 KU
Compound gear (train)
Crank & slider (any order)
2
1
0
 KU
1
0
(b) Rotational to reciprocal
Any order
(c)
Output speed =
 RNA for substitution
 80 48 
2000  
 RNA for answer

 = 156 rev/min
 20 15 
 RNA for VR1
from working
 RNA for VR2
4
3
2
1
Alt:
 RNA
T1 = 500 rev/min  RNA
20 x 2000 = 80 x T1
(d) Worm and wheel
15 x 500 = 48 x T2
T2 = 156 rev/min
0
1
0
 KU
(e)
Lubricating moving parts or bearings on shafts
(f)
1
2
 RNA
 RNA
 KU
correct
description
 KU
Rack and pinion
 KU
Worm and nut
Allow FTE from (b) if applicable
Page 7
1
0
2
1
0
Marks
KU RNA
8.
(a)
5
4
3
2
1
0
When Valve A is activated Valve C changes state causing the DAC to
outstroke slowly. When the DAC is fully outstroked it actuates Valve D which
sends a pilot signal to Valve C . This caused Valve C to change state and
instroke the DAC. If Valve A and Valve B are actuated the DAC will
outstroke quickly.
 RNA for each valid point up to a (maximum of 5)
(b) Valve C
 KU for each term any order
5/2 / pilot / pilot
3
2
1
0
Device E
Uni Directional Restrictor
 KU
1
0
(c)
(i)
1
0
 KU
Solenoid
(ii)
 KU
FTE from (c) (i)
1
0
r2
r2
=
=
ATOTAL
=
706 - 78·5
F
=
PxA
=
0·2 x 627·5
=
125·5 N
(d) A =
a =
 x 152
 x 52
 RNA for
=
=
706 mm2
78·5 mm2
=
627·5 mm2  RNA for answers
either calculation
 RNA for substitution (FTE)
 RNA for answer from working
Page 8
4
3
2
1
0
Marks
KU RNA
9.
(a)
V1
0×5
=
4×3 4×5
V1 R1
=
V2 R2
V1 =
 RNA for substitution
0×5× 4×3
4×5
= 478 Ω
2
1
0
 RNA for answer
from given working
(b) (i)
(ii)
 RNA
5 kΩ
IB =
V 3×2 - 0×7
=
R
1500
= 0·0017A
(1·7 mA)
(c)
1
0
(i)
Relay
(ii)
Base Resistor (Rb)
(iii)
Diode
 RNA for voltage calculation
 RNA for substitution
3
2
1
0
 RNA for answer
from given working
Allows the electronic circuit to control high
powered electrical circuits
Protects the transistor from high
current
Protects the transistor from back EMF/voltage
 KU
1
0
 RNA
1
0
 RNA
1
0
(d) Components will not be damaged/quicker to fix or adapt
design/etc
Page 9
 RNA
1
0
Marks
KU RNA
10.
(a)
Free body (diagram)
(b)
ΣCWM = ΣACWM
1
0
 KU
(1300 x 0·5) + (6000 x 1·5) + (1800 x 2) = R2 x 3
 RNA for substitution
650 + 9000 + 3600 = R2 x 3
R2 =
13250
3
= 4416·7 N
 RNA for transposition
 RNA for answer from given working
[END OF MARKING INSTRUCTIONS]
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