Department of Engineering and Mathematics
Session: 2020/2021
Module: 55-604480
Electronic Systems
Module Leader: Dr. Leon Shpanin
Assignment number/title: Coursework 1, Analogue
Academic contact for guidance: Dr. Leon Shpanin, L.Shpanin@shu.ac.uk
Maximum word count or number of pages: 10 pages
Percentage contribution to overall module mark: 15%
Deadline for submission: 14th January 2021, at 15:00
Method and Location for Submission: Blackboard submission plus Turnitin
Assessment (Individual & Group)
Deadline for return of feedback: Thursday, 04 February 2021
Module learning outcomes to be assessed:
• Design using appropriate methods, test and develop electronic circuits and systems to given specifications taking into account practical and commercial constraints on implementation
• Communicate effectively the outcomes of design and investigative work and use personal skills typically in the form of teamwork and project management applied to system design and implementation
References/recommended reading:
To find and access module resource lists online (RLO) search via https://shu.rl.talis.com/index.html
Resources including current reading lists may also be provided on Blackboard,
• Bogart, T. F., Beasley, J. S. & Rico, G. (2004) Electronic Devices and Circuits, 6th. ed., New Jersey,
Pearson.
• Gray, P. R., Hurst, P. J., Lewis, S. H. & Meyer, R.G. (2009) Analysis and Design of Analog
Integrated Circuits, 5th ed., New Jersey, John Wiley & Sons.
• Sedra, A. S. & Smith, K. C. (1998) Microelectronic circuits, Volume 1, Oxford, Oxford UP.
• Wakerly, J. (2006) Digital Design: Principles and Practices, New Jersey, Pearson
Electronic Systems - Analogue
Sound Level Meter Design Case Study
Objectives
The aims of this assignment are to:
• develop skills in the design of non-trivial analogue electronic systems
• introduce the use of behavioural models in the prototyping of analogue systems
• develop co-operative working in the design of non-trivial analogue electronic systems
Introduction
A sound level meter is an instrument for measuring noise. A microphone is used to convert the sound pressure variation into an electrical signal. This electrical signal is then processed with filters and detector circuits to give an averaged value that has good correlation with subjective response to the noise. The averaged value is displayed in decibels (dB) as the amplitude response of the ear has a very large range (approximately 107:1) and is approximately logarithmic. The aim of this case study is to investigate the design of the electrical processing stages of a sound level meter using analogue techniques and to evaluate the performance against given criteria.
The basic electrical elements of the instrument are shown in Figure 1.

Figure 1 Basic elements of a sound level meter

The electrical signal from the microphone is fed into the instrument via an attenuator that sets the basic operating range of the instrument. The signal is then passed to a frequency-weighting network, which is a band-pass filter that simulates the response of the human ear. The time averaging, detector and indicator section of the instrument either determines the rms value (with one of two possible time constants) or the instantaneous peak of the input signal. Both of these possible outputs are passed through a logarithmic amplifier to convert them to a decibel scale.
The performance of each element within the system can be compared with 4 different grades of instrument specified within this document. The overall instrument grade is determined by the element with the worst performance.
Assignment Task
Your task is to investigate the design of the electronic elements of an analogue sound level meter. The objective is to produce a design for a system that meets as high a grade of the standards specified in this document as possible, as effectively as possible. The instrument is to be powered by two standard PP3 style batteries (6F22) with battery life and system operation at the end of battery life as important performance indicators.
You must work collaboratively in a group to produce a functional simulation prototype of a complete system using the system modelling blocks contained within the OrCAD software. Using this high-level prototype you should characterize the system and determine the requirements specification for each element. Each member of the group should then individually design and simulate a component level circuit for at least one of the system blocks such that the overall functionality of your system is maintained when it is substituted into the original prototype design. These individual component level designs should then be combined to give a complete design at component level. Allowable components include operational amplifiers but NOT special purpose function chips such as rms-to-dc converters!
The work must be submitted in the form of a group report with the individual block design responsibilities clearly identified. Marks will be awarded according to the following criteria:
• the overall system specification and performance (group) 20marks
• the quality of the evaluation of circuit options, the rationale for the implementation selected and its performance relative to the specification (individual) 60marks
• the quality of the submission as a technical report (group) 20marks
The deadline for the submission of the report is 15:00, Thursday 14th January 2021. Submission will be electronic via the module Bb site - details to be confirmed. Feedback will be provided throughout the course and the final report feedback will be provided on or before Thursday 4th February 2021.

Report requirements
The report is to be submitted as a group assignment, with each of the contributors clearly identified. The specific area(s) where each individual has performed the detailed design must also be shown.
The criteria for assessment for each function block are indicated on the accompanying sheet. Ideally a number of options will have been considered and the rationale for the selection and design of the final circuit for each block should be presented. Designs which utilize standard component values (i.e. those from a recognized E series) and which consider the effect of component tolerance will be given a higher rating. The detail and results of appropriate tests should be presented to demonstrate the performance level achieved.
The report must include a summary sheet for the performance of the complete instrument. This must include the following information:
• the overall grade of the instrument
• the current consumption and expected battery life
• the estimated parts cost of the instrument
• the estimated design cost of the instrument based on a cost of £100/hour for each engineer
The Case Study will be assessed by how well each of the following areas is addressed in the report:
Block Feature Comments
Input ranges
overlap
evaluation
Frequency weighting accuracy
evaluation
RMS detector dynamic range
(including absolute linearity
value circuit time constant
if required) grade
evaluation
Peak detector risetime
grade
evaluation
Log amplifier dynamic range
evaluation
Battery life
evaluation
Report presentation
layout
Overall
Additional information and tests used to check the conformance with standards
General
The four grades of instrument specified in the standards correspond to a range of uses as follows:
Type 0 Laboratory grade instrument
Type 1 Precision grade instrument
Type 2 Industrial grade instrument
Type 3 Survey instrument
As the Type 0 instrument is intended for use within the controlled environmental conditions of a laboratory, it only needs to meet its specification at room temperature. The other instruments are intended to be used in a variety of locations and conditions and must therefore meet their specifications over a temperature range of –10?C to +50?C.
Microphone
The microphone has a nominal sensitivity of 10mVPa-1. This corresponds to an acoustic signal of 94 dB. The microphone has a dynamic range that extends from 30 dB to 150 dB. Your instrument should cover this range of signals by using a number of overlapping ranges that comply with later specifications for amount of overlap and tolerance.
Frequency weighting
The frequency weighting applied to sound level shall be A-weighting and that applied to the peak sound pressure shall be C-weighting. The weightings are specified in Table 1 with the associated tolerances given in Table 2. The C-weighting characteristic is ideally realized with two zeros at 0 Hz and two poles in the complex frequency plane situated on the real axis at 20.6 Hz to provide the low frequency roll-off and two poles on the real axis at 12,200 Hz to provide the high frequency roll-off. The lower frequency half-power or 3 dB point with respect to the 1 kHz reference is at 31.62 Hz and the upper frequency half-power point is at 7,943 Hz. Attenuation rates approach 12 dB per octave at both low and high frequencies.
The A-weighting characteristic is realized ideally by a further two zeros at 0 Hz and adding two poles on the real axis, at frequencies of 107.7 Hz and 737.9 Hz to the C-weighting characteristic.

Nominal frequency
(Hz) Exact frequency
(Hz) A weighting C weighting
10 10.00 -70.4 -14.3
12.5 12.59 -63.4 -11.2
16 15.85 -56.7 -8.5
20 19.95 -50.5 -6.2
25 25.12 -44.7 -4.4
31.5 31.62 -39.4 -3.0
40 39.81 -34.6 -2.0
50 50.12 -30.2 -1.3
63 63.10 -26.2 -0.8
80 79.43 -22.5 -0.5
100 100.0 -19.1 -0.3
125 125.9 -16.1 -0.2
160 158.5 -13.4 -0.1
200 199.5 -10.9 -0.0
250 251.2 -8.6 -0.0
315 316.2 -6.6 -0.0
400 398.1 -4.8 -0.0
500 501.2 -3.2 -0.0
630 631.0 -1.9 -0.0
800 794.3 -0.8 -0.0
1000 1000 0 0
1250 1259 +0.6 -0.0
1600 1585 +1.0 -0.1
2000 1995 +1.2 -0.2
2500 2512 +1.3 -0.3
3150 3162 +1.2 -0.5
4000 3981 +1.0 -0.8
5000 5012 +0.5 -1.3
6300 6310 -0.1 -2.0
8000 7943 -1.1 -3.0
10000 10000 -2.5 -4.4
12500 12590 -4.3 -6.2
16000 15850 -6.6 -8.5
20000 19950 -9.3 -11.2
Table 1 Frequency weighting characteristics in decibels

Nominal frequency
(Hz) Type 0 Type 1 Type 2 Type 3
10 +2; -? +3; -? +5; -? +5; -?
12.5 +2; -? +3; -? +5; -? +5; -?
16 +2; -? +3; -? +5; -? +5; -?
20 ?2 ?3 ?3 +5; -?
25 ?1.5 ?2 ?3 +5; -?
31.5 ?1 ?1.5 ?3 ?4
40 ?1 ?1.5 ?2 ?4
50 ?1 ?1.5 ?2 ?3
63 ?1 ?1.5 ?2 ?3
80 ?1 ?1.5 ?2 ?3
100 ?0.7 ?1 ?1.5 ?3
125 ?0.7 ?1 ?1.5 ?2
160 ?0.7 ?1 ?1.5 ?2
200 ?0.7 ?1 ?1.5 ?2
250 ?0.7 ?1 ?1.5 ?2
315 ?0.7 ?1 ?1.5 ?2
400 ?0.7 ?1 ?1.5 ?2
500 ?0.7 ?1 ?1.5 ?2
630 ?0.7 ?1 ?1.5 ?2
800 ?0.7 ?1 ?1.5 ?2
1000 ?0.7 ?1 ?1.5 ?2
1250 ?0.7 ?1 ?1.5 ?2.5
1600 ?0.7 ?1 ?2 ?3
2000 ?0.7 ?1 ?2 ?3
2500 ?0.7 ?1 ?2.5 ?4
3150 ?0.7 ?1 ?2.5 ?4.5
4000 ?0.7 ?1 ?3 ?5
5000 ?1 ?1.5 ?3.5 ?6
6300 +1; -1.5 +1.5; -2 ?4.5 ?6
8000 +1; -2 +1.5; -3 ?5 ?6
10000 +2; -3 +2; -4 +5; -? +6; -?
12500 +2; -3 +3; -6 +5; -? +6; -?
16000 +2; -3 +3; -? +5; -? +6; -?
20000 +2; -3 +3; -? +5; -? +6; -?
Table 2 Tolerances on frequency weighting characteristics given in Table 1 for each instrument type, in decibels

Level range
When a level range control is included, it shall introduce errors less than those in Table 3 for all settings with reference to a range setting specified by the designer.
Frequency
(Hz) Type 0 Type 1 Type 2 Type 3
31.5 - 8000 ?0.3 ?0.3 ?0.3 ?0.3
20 - 12500 ?0.3 ?0.3 — —
Table 3 Tolerances on level range control accuracy in various frequency ranges, in decibels
When a manual level range control is included in a sound level meter, ranges shall overlap by at least 5 dB if the step of the level range control is 10 dB and by at least 10 dB if the step is greater.
Indicator and detector characteristics
The time-weighting characteristics of the detector indicator shall be such that it will respond to tone bursts as specified in Table 4 and to a suddenly applied signal, or step in signal amplitude, with overshoot as specified in Table 5.
Detector –indicator characteristic Duration of test tone burst
(ms) Maximum response to test tone burst referred to response to continuous signal
(dB) Tolerances on maximum response for each instrument type
(dB)
0 1 2 3
continuous 0
F 200 -1.0 ±0.5 ±1 + 1
- 2 + 1
- 3
50 -4.8 ±2 — — —
20 -8.3 ±2 — — —
5 -14.1 ±2 — — —
S 2000 -0.6 ±0.5 — — —
500 -4.1 ±0.5 ±1 ±2 ±2
200 -7.4 ±2 — — —
50 -13.1 ±2 — — —
Table 4 Response to tone bursts
Detector –indicator characteristic Type 0 Type 1 Type 2 Type 3
F 0.5 1.1 1.1 1.1
S 1.0 1.6 1.6 1.6
Table 5 Maximum overshoot in decibels
The tone burst used for evaluating the time-weighting characteristic shall consist of an integer number of cycles of a 1 kHz sinusoid.
When a sound level meter is equipped for measuring peak values, the onset time of the detector shall be specified by the designer. A Type 0 instrument shall be such that a single pulse of 50 µs duration produces a deflection no more than 2 dB below that produced by a pulse having a duration of 10 ms and equal peak amplitude. This requirement shall be met for pulses of both polarities. For other types, the onset time should be such that a single pulse of either polarity of 100 µs duration produces a deflection no more than 2 dB below the deflection produced by a pulse having a duration of 10 ms and equal peak amplitude.
The range of the indicator shall be at least 15 dB. At least 10 dB shall be specified as the primary indicator range by the designer.
The linearity of the system consisting of the detector-indicator and any manual or automatic range controls shall be tested and shall satisfy the requirements of Table 6. The reference level for testing linearity is the reference sound pressure level.
Readings Type 0 Type 1 Type 2 Type 3
Inside primary indicator range 0.5 1.1 1.1 1.1
Outside primary indicator range 1.0 1.6 1.6 1.6
Table 6 Tolerances on level linearity referred to the reference sound pressure level in the frequency range 31.5 Hz to 8000 Hz (20 Hz to 12,500 Hz for Type 0), in decibels
The instrument shall satisfy a test for differential linearity. Differential linearity error is measured between any two arbitrarily chosen points that are up to 10 dB apart, in the range of the indicator. The maximum error, both inside and outside the primary indicator range, permitted for each type of sound level meter for points separated by 1 dB and for points separated by up to 10 dB is given in Table 7.
Readings Type 0 Type 1 Type 2 Type 3
Inside primary indicator range, points separated by 1 dB ?0.2 ?0.2 ?0.3 ?0.3
Inside primary indicator range, points separated by 1 dB to 10 dB ?0.4 ?0.4 ?0.6 ?1.0
Outside primary indicator range, points separated by 1 dB ?0.3 ?0.3 ?0.4 ?0.4
Outside primary indicator range, points separated by 1 dB to 10 dB ?0.6 ?1.0 ?1.5 ?2.0
Table 7 Tolerances on differential level linearity in the frequency range 31.5 Hz to 8000 Hz (20 Hz to 12,500 Hz for Type 0), in decibels