AU530552B2 - Wave level measuring apparatus - Google Patents

Description

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MICROCOPY RESOLUTION TEST CHART NATO-NAL BUREAUOF STANDARDS-1963-A

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Form I Regulation 9. APPLCATO~.ACCED AN4D AMAENDMENTS

,4 .COMMD~ON WEALTH OF AUSTRALIA

PATENTS ACT 1952-1969

APPLICATION FOR A P)ATENKT

45918/79 I/fMINISTER FOR PUBLIC WORKS FOR THE STATE OF NEW SOUTH WALES.

Of Parliament House, Macquarie Street, Sydney, New South Wales, 2000

hereby apply for the grant of a Patent for an

invention entitled/ 009,F1 ETE AFER PROVISIONJAL :P[GWICJA11ON M& "WAVE LEVEL MEASURING APPARATUS"

which is described in the accomparnjing Provisional

specification.

MY address for service is Messrs. Griffituh, Hassel

Frazer, 323 Castlereagh Street, SYDNEY 2000, Australia.

Dated this 4 tth day of April 19 78.

MIN-ESTER FOR PUBLIC WORKS FOR THAE STATE OF NEW SOUTH WALES AUSPWRN 7A byT hiyetent,,-Attorney:

7 APR

of GRILFFITH, HASS~EL FRAZER. (Fellows, Institute of Patent Attorneys of Australia)

The Com11n.OSioner of PabonLS Commonwealth of AusUralia.

COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 (AS AMENDED).

DECLARAT T ON IN SUPPORT OF PATENT APPLICATION

In support of an application by MINISTER FOR PUBLIC WORKS FOR THE STATE OF NEW SOUTH WALES for a patent for an invention entitled "WAVE LEVEL MEASURING APPARATUS".

The Honourable Laurie John Ferguson, Minister for Public Works for the State of New South Wales of Parliament House, C 0 Macquarie Street, Sydney, New South Wales, do solemnly and

sincerely declare as follows:

1. This application is made in the name "MINISTER FOR PUBLIC WORKS FOR THE STATE OF NEW SOUTH WALES" and I am the present holder of this office. 2. The actual inventor is Andrew John Allan of 2C-29 Quirk Road, Manly Vale, 2093

and the applicant is entitled to make this application by virtue of Section 34 of the Patents Act, namely the applicant would be entitled to have any patent granted to the inventor in respect of the present invention assigr to the applicant by virtue of the fact that the inventor made the invention in the course of his employment and duties in the Department of Public Works.

Declared at 4 this J, day oft4/f 1982.

L.:4*Z Ferguso 1 Mirdaiter fo 3lblic Works for the tate of New South Wales

means for converting the output pulses of the mcnostable device to an output voltage/. and input connection means for

I r.ili'l,)ir. run rUDLit WU NJ rUK Int 1 t I Al t Ur I'tW ZUUIM WALES

(21) 45918/79 53,552 (22) 7.4. 78 (23) 6.4.79 (24) 7.4. 78 (43) 11.10.79 (44) 21.7 .83 (51)2 GO1R 27/26 GO1F 23/'6 G010 3/10 G01D '/2 46 (72) ANDREW JOHN ALLAN (74) GH (56) 45810/79 G01F 40314/78 519054 LO1R 36124/78 G01F, GOlD, GO1R

(57) C ai im

1. An electrical circuit comprising means for connection to

a stable voltage supply, an oscillator for producing a

substantially constant frequency output, a monostable device

connected to the oscillator so as to be triggered to produce

an output pulse for each cycle of the oscillator, means for

converting the output pu'ses of the monostable device to an

output voltage, and input connection means for connecting a

variable capacitance device into a timing circuit of the

monostable device for varying the length of the output pulse

of the monostable device in a manner substantially linearly

with variation in the capacitance of the variable

capaci ance device.

D1 26 4

A115/71/5

purposes.

53Of52 COMMON\WEALTH OF AUSTRALIA Form

PATENTS ACT' 1952-69

COMPLETE SPECIFICATION (ORIGINAL)

FOR OFFICE USE: Class Int. Class Application Number Lodged 45918/79

Complete Specification Lodged C Accepted Published Prjority Tb~i d~x~ i~;the

elated Art C, 0 C and i' (t tI 1.;

I

0-

TO BE COMPLETED BY APPLICANT Name of Applicant MINISTER FOR PUBLIC WiORKS THE STATE OF NEW SOUTH WALES

0 Address of Appli,ant: Parliament House, Macquarie Stieet, Sydney, New South Wales, 2000

Actual Inventor: ANDREW JOHN ALLAN

Griffith, Hassel Frazer,

.,A6dress for Service: 323 Castlereagh St., SYDNEY N.S.W. 2000 AUSTRALIA

Complete Specification for the invention entitled:

"MEASURING APPARATUS"

The following statement is a full description of this invention, with the best method of performing it known to me/us:-

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the arra:.gement being such that two of the diodes indicate

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The present invention relates to apparatus for deriving

a signal corresponding to the capacitance of variable

capacitance device.

One application of the present invention is for providing

a voltage signal for operating a pen recorder, oscilloscope,

C or data processing machine for indicating the variation in CO v4 the capacitance of a device such as a liquid level capacitance

detection probe. Liquid level detection probes of a capacitance 0 06

ro '9 00 r type are known and have been used for applications such as

*00000 10 measuring even quite rapid changes in level due to wave 900 o 0 9

motion "Jt only in laboratory simulation experiments but 00 also for measuring naturally occurring waves in bays, harbours,

rivers and the like. A known cype of probe comprises a 09

0 supporting frame work carrying a thin long U-shaped loop of

0000 15 insulated wire adapted to contact the water or other liquid, '$900 the height of the liquid affecting the capacitance of the a

device. 0900 0

0 The present invention is concerned with providing an 009 improved apparatus for use with capacitance detection probes.

Broadly speaking, the present invention consists in an

electrical circuit comprising means for connection to a

stable voltage supply, an oscillator for producing a substantially

constant frequency output, a monostable device connected t

the oscillator so as to be triggered to produce an output

pulse for each cycle of the oscillator, &i ntcgratEr o'

inteqrating the output of the monostab device, means for

~reerniectin+ -Ile nut+-"1t nf fht intp-g-r an apparat fu

psol R7

41~ 2 means for converting the output pulses of the mcnostable device to an output voltage/, and input connection means for connecting a variable capacitance device into a timing circuit of the monostable device for varying the length of the output pulse of the monostable device in a manner substantially linearly with variation in the capacitance of the variable capacitance device. The circuit is intended to be operated with the maximum length of the monostable output o~o pulse less than the frequency of the oscillator.

Preferably, the monostable device is a solid-state integrated circuit and the oscillator is preferably an o eQ

astable solid-state intagrated circuit and for convenience the invention is implemented using a single integrated

circuit having 0'-al timing circuits connected in a 15 particular manner whereby an embodiment of the invention is

provided. Although the converting means itself could be provided by a pen recorder, preferably a main charging capacitor is

provided between the output line of the monostable device

.'ZO0 a and a common earth. Furthermore embodiments of the invention may advantageously include a capacitor connected

across an amplifier to which the output of the main charging capacitor is presented. With great advantage, many additional features may be incorporated in embodiments of the invention which are

especially useful when the probe is a wave height detection

VAUbULUJ eluDouimeuL is suppliea to an ampirier nav-ng

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3a therewith a variable resistance so that the output of the amplifier can be adjusted for zero setting the apparatus.

A further amplifi.er receiving the output from the first

amplifier furthermore advantageously has associated therewith

a variable resistance whereby the gain of the second amplifier

M_ can be adjusted. For further smoothing out ripples in the 00 voltage output, the second amplifier can also have an

ac AJ 4 o integrating capacitor connected across the amplifier.

To permit the plotting of both the peak and trough heights of a series of waves which are incident on the A A capacitance probe, the voltage signal may be fed to a pair o CDC of processing circuits. The first amplifier is set to 0o0 provide a zero voltage output level for a mean height of

water. The first circuit comprises an amplifier with a

diode for passing positive current only and this is c Innected

to a second amplifier from which the wave peak height is indicated by a voltage signal, A large time constant is provided for the second amplifier by a resistance, capacitance

network. The second circuit is similar except that the

diode is connected to pass negative signals only.

A further advantageous feature is provided with a

separate circuit connected to the output of the integ-ateor

and comprising a series of light emitting diodes connected

to respective outputs of a four chonnel amplifier. Two of the diodes which are conveniently of red colour are used to

D indicate excessively high or low voltage signals and two diodes are provided to indicate signals which are just positive or just negative and within an operational rarge.

A fifth diode can be provided to indicate when the voltage

signal .s high but still within an operational range.

For illustrative purposes only a preferred embodiment o of the invention will now be described, by way of example,

OO with reference to the accompanying drawings, of which:

SFigure i is a block diagram of a circuit embodying the

invention;

.ooo:0 10 Figure 2 is a detailed circuit diagram of the embodiment .O of Figure 1 and

S0. Figure 3 is a schematic block diagram of the integrated e circuit IC1 of Figure 1.

Referring first to Figure 1, the circuit is shown

connected to a variable capacitance probe 1 for detecting variations in the height of a body of water into which the

probe is partially immersed, the probe 1 being connected to

earth as indicated by 2 and connected to a monostable device

3, the value of the capacitance at a particular point in

time determining the pulse length of the output of the

monostable device. An astable multivibrator 4 acts as an

oscillator of fixed frequency for triggering the monostable

device, the circuit being powered by the output of an integrated

circuit voltage regulator

The output from the monostable device 3 is passed to a

ipntgrato 6, the output of which is a-voltage indicative of

the capacitance value at that time of the probe 1. The

VT 0 output ofitegrater 6 is passed to an amplifier 7 having a variable resistance associated therewith to permit zero setting of the apparatus, the output of this first amplifier being passed to a second amplifier 8 which has a gain setting function again by adjustment of an associated le resistance. O T-4 The output from the second amplifier 8 is thus .n

'n amplified voltage signal of zero level for the mean water

height detected by the probe (this will usually be conveniently

10 arranged near the centre of the probe), the voltage signal

Sis a positive value when the water height is above the mean 0 o position and a negative value when the water level is below

the mean position. The output is passed to a light emitting go.., diode display 9 having diodes connected across the outputs

of a four channel amplifier for easy visual indication of

oa the order of magnitude of the output voltage signal, the

a. output simultaneously being supplied also to a chart recorder

through connection line 10 (which plots the variation in

voltage and also to a further circuit 11).

The circuit 11 comprises a four channel amplifier, two

amplifiers of which are connected in sequence for providing

an output indicative of the wave peaks (the circuit including

long time constants to permit averaging over a substantial

period of time 20 seconds) and the other two amplifiers similarly being connected but to indicate the troughs of the

wave system being monitored by the probe 1.

The detailed circuit on Figure 2 does not include the

probe which is connected to the capacitive probe input 12.

The circuit of Figure 2 is built around an integrated

circuit IC 1, the preferred unit being a Signetics dual

timer linear integrated circuit 556. This circuit comprises

dual timing circuits, a block diagram of which is given in

rS Figure 3, each separate part of the cjrcrit including a

CO flip-flop FF. The integrated circui_ ic is connetad as a .D c a a '4 Sshown in Figure 2 For the purpose of providing a reliable

a a instrument, a stable voltage supply of 7 volts is prrvided

o 10 by integrated circuit IC 2 which is connected to +15 volts o a 00 supply as indicated.

A variable trimming capacitor Cl is connected in

PC a.l I parallel with the probe 1 for the purpose of adjusting the

circuits to suit the chosen probe and indeed to permit the

15 circuit to be readily adjusted to suit a selection of probes 4 ba of different capacitance. A further capacitor 13 is also

connected in parallel with the probe, the type and value of C

Is a 06 this capacitor being carefully chosen to compensate for what

'a' would otherwise be a drift in zero setting of the apparatus

with increasing temperature. In fact the capacitor chosen

is a Philips ceramic capacitor 632 series type 58689 which

has a negative temperature coefficient of 750 parts

per million per degree C.

The output from the monostable device A of IC 1 is

passed to a main integrating capacitor 6, and the resulting

Jvolta-3 presented to a first amplifier 7 which is an integrated circuit. This amplifier is connected to a variable resistor

14 for the purpose of adjusting the amplifier output to be

zero volts at a mean height of the waves or water to be

detected by the probe. For further reducing the voltage

ripple which will be present at the input to the amplifier

0) 7, a further capacitor 15 is connected across the amplifier 00 and in a sense this further capacitor also has an integrating

-4 function.

2For adjusting the gain of the apparatus, the second 10 amplifier 8 receives the output from the first amplifier 7

and an additional c.pacitor 16 is connected across this 00

Z amplifier for yet further reducing the ripple in the voltage signal. The second amplifier 8 also has a variable resis-or 17 to adjust the gain of the amplifier circuit.

The output from the second amplifier is passed to the 000*

iED display 9 comprising an integrated circuit four channel

amplifier LM324 connected in the configuration indicated in Figure 2 with a series of light emitting diodes of selected

colours. The configuration is such that the orange diode is

illuminated when the output voltage is just less than zero volts but is turned off and the yellow diode becomes illuminated

as the voltage becomes just positive. This is the normal

operational situation. At +5 volts output, it is the green

diode alone which becomes illuminated. At an excessively

high output voltage (either positive or negative) one of the

red diodes becomes illuminated to indicate that the circuit

is saturating and is outside the normal operational mode.

This would be the case if the probe was totally immersed in

water or entirely out of the water.

The output from the second amplifier 8 is also connected

to a further integrated circuit LM324 which comprises two

circuit portions. The first circuit portion comprises

amplifier Al, forward biassed diode 18, amplifier A4 and a I- long time constant timing circuit comprising resistor 19 and

capacitor 20. The second circuit portion is similar and s* ,a comprises amplifiers A2 and A3 with a reverse bias diode 21, *d amplifier A3 having associated therewith the timil j network ft

ft f comprising resistor 22 and capacitor 23. The outputs provided ft ft 6 00l ci tf from the respective circuit portions at 24 and 25 respectively

comprise a signal indicating the average wave peak and wave

trough heights but would also indicate any rapid changes in

wave height by a sudden rise in the signal level.

The circuit has further outputs namely a d.c. output 26

and an a.c. output 27 for connecting the oatput of the

second amplifier 8 for example, to a chart recorder. 0 The circuit is protected to some extent against voltage

transients since every input and output has a passive L

section L-C filter fitted.

The whole circuit can conveniently be mounted inside a

sealed enclosure on a printed circuit board, a coaxial

connection being provided for connection to the probe.

For measuring small waves of the order of 2 millimetres

in height in a laboratory model, the probe might consist of

enamelled wire as small as 39 swg. For waves of a few hundred millimetres height, teflon or polyethylene insulating 0, wire can be used and good linearity can be cDtained. 00 4 Embodiments of the invention can be reasonably easy to manufacture and can provide good stability to temperature coupled with robustness and easy-portability.

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Claims (1)

1. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. An electrical circuit comprising means for connectiou Izc,

   a stable voltage supply, an oscillator for producing a substantially cons~tant frequency output, a monostable devir- connected to the oscillator so as to be triggered to prodice

   an output pulse for each cycle of the oscillator, meanis fort converting tile outpW. 2i'ses of the monost t7-, device -to aa output voltag-~ and inpult conncrction meanz f-)r connectP".riga vari.\ble capacitance device tinto a tuang circuit of the To monostable device for varying the length of the output pulse of-.the monostable device In a manner substantially linearly with variation in tlie capacitance of t'Lxe variable capacir.ance device. 2. electrical circuit as cl&-Lmed in claim 1 wherei.n thea monost.cble device and the oscillat*,,r are rpj::v-,.ded by a s.ngle integrated cizcuit. having dual tl3ning circuits connected such .at the electrical circuit is formed. 3. Ar:, sE.isctrical circit as claimed in claim 2 wherein said cionvertiiAg means includea a main charging capacitor provided Ii

   between anP output line of the monstable device and an earth 003,0

   connection. 4. An electrical circuit as claimed in claim 3 wherein a further capacitor is connected across an amplifier to which the outpux: or the main charging rnapacitor is presented. S. An electrical circuit as claimed in claim 4 wherein a variable resistance is associated with the amplifier so that the output of the amplifier can be adjust..I: for zero setting

   1J1 mentioned amplifier, nl the further amplifier having an associated OO Svariable resistance whereby the gain of the second amplifier can be adjusted, and the further amplifier has an associated

   Sintegrating capacitor connected across the further amplifier

   for smoothing out of ripples in the voltage output.

   7. An electriial circuit as cla4-ed in any one of the I° preceding claims and including a pair of processing circuits

   Sadapte to permit the plotting of both the peak and trough

   3 heights of a series of waves in a liquid medium,/ the apparatus

   Srthr icluding a variable capacitance probe adapt .d to be

   inserted into the liquid medium as such that the capacitance

   varies with liquid height relative to the probe.

   8. An electrical circuit as claimed in claim 7 wherein the

   first processing circuit comprises an amplifier and an

   2- associated ciode for passing positive current only to a second

   amplifier hich a liquid wave peak height is indicatedE by-

   .avoltage cignal and the second circuit corresponds except

   that the diode is connected so as to pass negative signals

   only.

   S An electrical circuit as claimed in any one of the

   preceding claims and comprising a series of light emitting

   diodes connected to the respective outputs of a four channel

   amplifier which is connected to the output of the integrator,

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   the arranLgement being such that two of the diodes indicate

   respectively excessively high or low voltage signals, two of

   C the diodes indicate signals which are just positive or just C00 r-4 negative and within an operational range.

   Apparatus substantially 's herein described with reference

   to the accompanying drawings.

   DATED this 6th day of April, 1979.

   Bp B o p

   MINISTER FOR PUBLIC WORKS FOR THE STAT,. OF NEW SOUTH WALES By their Patent Attorney:

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