Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DATA LOGGING APPARAT~S
The present invention relates to data logging apparatus
and particularly, but not exclusively, to data logging apparatus
for use in cathodic protection surveys for the measurement of
pipe-to-soil potentials.
In cathodic protection surveys measurement of pipe to
soil potential differences with a buried pLpe is usually
achieved by measuring the potential between a test lead
connected between the underground pipe and a measuring
electrode, usually a copper-copper sulphate (Cu-CuS04~
electrode which provides contact with the soil or electrolyte
e.g. water. These measurements are repeated on the surface at
various intervals over the route of the pipe perpendicular to
the pipe and the potentials measured over the distance
constitute the ~survey~. To facilitate surveying a reel of
electrical wire is carried by the surveyor for providing
electrical connection to the test lead, the reel also including
an odometer for accurate distance measurement. At each desired
location the surveyor contacts the soil with the measuring
electrode and the pipe-to-soil potential difference i~ measured
by a voltmeter. The measured voltages can be recorded on a tape
recorder carried in a backpack by the surveyor, or transmitted
to a remote location by a radio receiver or merely recorded in
writing. This apparatus has several disadvantages firstly the
; 25 surveyor requires to carry a backpack for the tape recorder or
radio transmitting equipment, which is cumbersome; data is
continuously entered in accordance with the odometer reading
which is unnecessary and therefore wasteful; writing down of
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data is slow and is difficult in inclement weather or difficult
terrain and transfer of writing data is labour extensive and a
high probability of errors occur; the use of the odometer,
whilst giving accurate distance measurement is unnecessary and
adds to the complexity of the equipment. With regard to the
acquisition of the data itself, the odometer driven apparatus
does not provide any facility for correction of a wrong entry
nor is it directly interfaceable to a computer for processing of
the data.
U.S. Patent No. 4,322,805 to Rog discloses an
electrical survey method and apparatus which attempts to solve
some of these abovementioned problems, by using apparatus which
automatically measures and records pipe to soil potential
difference and distance information. The apparatus includes an
electronics package which has a printed circuit card assembly
with a microcomputer control, and a tape drive and bulky battery
pack for recording the data which is mounted in a backpack. The
operator can enter specific commands relating to topographical
features via the keyboard into the microcomputer and into the
tape memory. The potentials recorded are displayed to the
operator, as well as the status of the apparatus and any error
conditions. With this apparatus the potentials are
automatically sensed and stored, which can provide considerably
more data than is required for meaningful analysis. This
apparatus also requires wire support means and an odometer which
again is unnecessary and provides excess dataO In addition, as
magnetic tape is used as the storage medium, this is bulky and
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requires the use o~ the backpack. Ma~netic tapes are relatively
sLow to process an~ are prone to problems such as tape drive
spee~ consistency, loss of ~agnetisation and only a single
record of the survey. This apparatus is considered not to have
presented ef~icient solutions for the problems of recording and
storing electrical potential data.
An object of the present invention is to obviate or
mitigate the abovesaid disadvantages.
According to a first aspect of the present invention
there is provided data logging apparatus comprising, input means
for receiving an analo~ signal representive of a parameter to be
measured, analog to digital conversion means associated with the
input means for digitising the analog input signal, solid state
memory means connected to the analog to digital converter or
storing the digitised signal therein, microprocessor control
means connected to the analog to digital converter and to the
solid s~ate memory means for controlling the recording and
storage of data by the data logging apparatus in accordance with
a predetermined algorithm.
Preferably, the data logging apparatus includes
keyboard means and display means, the keyboard means being
operable by a user whereby data to be entered and stored is
displayed on the display means, and the displayed data is stored
at the discretion of the user.
Preferably also, the apparatus includes an eraseable
programmable read-only-memory (EPR3M), the EPROM containing said
predetermined algorithm.
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r~referab]y also, the data lo~in~ a~paratus is housed
in a portable hand held unit.
According to a second aspect of the invention there is
provided a system for data acquisition, storage and trans~er
comprising data logging apparatus for measuring analog data and
recording said analog data in digital format in first solid
state memory means, second solid state memory ~eans external to
the data logging apparatus and connectable to the first solid
state memory, microprocessor control means connected to the
first memory solid state means and connectable to the second
solid state memory means~for controlling the copying of data
from the first solid state memory means to the second solid
state memory means in accordance with a predetermined algorithm.
Preerably, the second solid state memory means is an
erasable-programmable read-only memory (EPROM).
According to a third aspect of the present invention
there is provided a system for data acquisition, transfer and
analysis comprising data logging apparatus for measuring and
recording data in digital format in a first solid state memory,
data transfer means connectable between the first solid state
means and a telecommunication line, said data transfer means
comprising modulation means connected to one end of said
telecommunication line for enabling the data stored in the first
memory means to be transmitted along said telecommunication
lines in serial form, and demodulation means connected to the
other end of said telecommunication line for converting said
tFansmitted data into a format suitable for computer analysis.
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Preferable, demo(~ulation mearls is connectable to a
computer, said computer bein~ programlned in accordance with a
predetermined al~orithm to p~esent a visua] display of the
analysis of said data.
~ ccording to a fourth aspect of the invention there is
provided a method of recording, processing and analysing survey
data comprising,
measuring a first parameter, visually displaying said
first parameter and storing the first parameter at the
discretion of a user in first solid state memory means,
recording and displaying a signal representative of a
second parameter at a discretion of a user in the first solid
state memory means,
copying the data stored in said first solid state
memory to data analysis means, said data analysis means
analysing the first para~eter and the second parameter, said
analysis including a comparison of the variation in first
parameter with a variation in the second parameter, and
visually displaying the result of said comparison7
Preferably, said data method includes the step of
copying from said first solid state memory means to an EPROM,
and said EPROM is located in a computer.
Alternatively, said method includes the step of copying
data from said first solid state memory means to a
modulator/demodulator unit via the telephone lines to a computer.
According to a fifth aspect of the present invention
tùere is provided a method of measuring and processing data from
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an electrical survey of pipe to soil potential differences
comprising
measuring a potential dif~erence between a pipe and an
electrolyte at a first location, converting the analog signal to
a digital signal, storing the digital signal in first solid
state memory means, measuring a second potential difference
between the pipe and soil at a second location and converting
the second analog to a digital signal and storing the digital
signal in said solid state memory means,
repeating the measurement for the potential differences
at other desired locatiohs,
recordiny data representative of at least some of the
measurement locations,
processing the stored data to provide a relationship
between the measured potentials and the measurement locations,
in accordance with a predetermined algorithm, said algorithm
processing the data such that distances between successive known
locations are divided into a number of substantially identical
distances, and the potential readings are allocated at
successive intervals.
displaying the relationship in the form of a graph or
table of measured pipe to soil versus distance along pipe from a
reference point.
Preferably, processing include.s comparing the measured
potentials with at least one at predeterlnined threshold, and
displaying the data in a format in accordance with an algorithm
depending on the results on the comparison
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An embodiment of the present invention will now be
described by way of example with reference to the accompanying
drawings in which:-
FIG. 1 is a schematic perspective view of an electrical
S survey being undertaken of a buried pipeline by portable logging
and recording apparatus of the invention.
FIG. 2 is a perspective top view of the portable
logging apparatus showing its relative si~e;
FIG. 3 is a typical graph of potential versus distance
obtained using the apparatus of Figs. 1 and 2;
FIG. 4 is a schematic diagram of the logging device
linked by a modem to a computer to analyse the data in graph
form as shown in Fig. 3.
FIG. 5 is a schematic block diagram of the data logging
apparatus and showlng its ~unctional relationship to external
equipment;
FIG. 6 is a diagram of part of the data logger
circuitry showing the input circuitry to the data logger, an
analog to digital converter, and circuitry for powering the
device;
YIG. 7 is a circuit diagram of another part of the
circuitry showing a microprocessor, a random access memory for
storing the digitised data, and an EPROM containing t,he
algorithms for operating the data logger unit.
FIG. 8 is a circuit diagram of another part of the
circuitry and shows the keyboard, decoder circuit, shit
regîsters for the liquid crystal display, and the liquid crystal
display itself;
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FIG. 9 is a circuit ~iagram of an EPROM program~ner
circuit which is connectable to the logginy circuitry to receive
logged data from the randorn access memory.
FIG.10 is a flow chart illustratinq the main steps in
the measurement operation of the circuitry of the apparatus.
FIG. 11 is a flow chart of a sub-program (INTCLA) of
the steps involved in initialising the system and reading and
storing data in the random access memory entered via the
keyboard;
FIG. 12 is a flow chart of a sub-program (INTPOT~ of
the steps involved in reading the potentials and storing in the
random access memory;
FIG. 13 is a flow chart of a sub-program ~ENTER) of the
steps involved when data is entered into the logging unit random
access memory;
FIG. 14 is a flow chart (BLINK) of steps of a routine
which causes the display to blink twice when an entry is stored
in the random access memory;
FIG. 15 is flow chart (RETNOR) of steps of a routine
used in the flow chart of Figs. 11, 12, 13 and 14 to return to
normal mode;
FIG. 16 is a flow chart (CODE COMMAND) which controls
flags 0, 1, 3 and 4 to permit a code display routine (AFFEDj to
be called;
FIG. 17a IS a flow chart (AFE`CD) of steps used to call
a code dLsplay routine used in the flow charts of Fi9s. 13 and
14;
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F~IG. 17b is a ~low chart of routine (AFFI) used to call
on display;
FIG. 18 is a ~low chart of a program (MEMDIS) of the
steps used to the available memory in the random access memory,
FIG. 19 is a flow chart of the steps used to check the
battery voltage;
FIG. 20 is a flow chart (AFFER) of steps of an error
display routine;
FIGS. 21, 22 and 23 are flow charts of sub-routines for
AFFDEL, APPI, DELX and DELS50 referred to in the AFF~ routine;
FIG. 24 is a sub-program ~RECALL) of the steps involved
when data is recalled from the random access memory to display
the last reading entered;
FIG. 25 is a sub-program (CANCEL) of the steps used in
the cancel command
FIG. 26 is a flow chart of a sub-program (DUMPEPR0~1) of
the progress steps used to transfer data from the RAM to an
external EPROM.
FI~. 27 is a flow chart of a sub-program (PR07) of
program steps used to terminate transfer of data to the EPROM
and return to normal, and
FIG. 28 is a flow chart (DUMP RS232) of the program
s~eps used to transfer data from the RAM to a modulator;
FIG. 29 is a list of the flags used to control
operation of the decision making processes in the programs.
~ efecring now to the drawings the data logging
apparatus and its application to survey of pipe-to-soil
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potential differences will be described. As illustrated by
Fig. 1 data logging apparatus in the form of a hand-held unit 50
is carried by a surveyor 52 who is walking on the surface 54
along~he route of a buried pipeline 56. The objective of the
survey is to record potential differences between the pipeline
56 and reference electrode 62 and to identify locations of the
pipeline which have possible corrosion problems and to assess
the effectiveness of the cathodic protection system. The
pipe-to-soil potentials are measured between an insulated test
lead 60 which is located on the surface but which contacts the
pipe 56 and is connected by a wire 66 to a copper-copper
sulphate (CUCUSO4) reference electrode 62 carried on a staff
64 by the surveyor 52, which electrode makes contact with the
ground surface 54. The wire 66 is stored on a power reel 68
which can be driven to rewind ~he wire after completion of the
survey and is connected to one input terminal 69 in the end 71
(Fig. 4) of the unit 50, the wire being anchored to a belt 67 of
the surveyor so t,hat it is pulled from the reel as he walks
forward. The output of the measuring electrode 62 is connected
via a wire 70 to another input terminal 69 of the data logging
unit 50. As shown in Fig. 2 the data logging unit 50 is
dimensioned so that it is easily carried in one hand and may
also be located in a belt-pouch 72 worn by the surveyor. It
basically comprises a durable plastic casing with a sixteen key
sealed keyboard module 76 and an 8 element liquid crystal display
78. Data recorded by the unit 50 is stored digitally in a random
access memory ~RAM) therein, as will be described in more detail
hereinafter, the stored data being transferable to a computer for
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processing to provide a pipe-to-soil survey plot as shown in
Fig. 3. Figure 3 is a typical graph of pipe-to-soil potential
(-volts) versus distance along the pipeline in kilometers. The
potential is seen to vary considerably with distance with the
potential falling beneath the 0.35 (-volts) value around 1
kilometer and 3.6 kilometer respectively, this being indicative
of possible corrosion problems at these locations. Also shown
on Fig. 3 are codes of respective topographical locations along
the pipeline, and this data is used to provide additional
reference locations for the pipe-to-soil potential
measurements. ~or example, there is a foreign crossing, coded
C4, at the 1 km chainage location and a railroad crossing, coded
C3, at the 2.684 km chainage location. Referring again to
Fig. 4 the data logging unit has a rear output port 74, from
which stored data can be transferred, as will be described in
more detail hereinafter. The data is transferrable to an
erasable-programmable-read only memory (EPROM) (not shown~ or to
a modulator 76 for transmission over telephone lines 78 to a
host computer 80 which may include its own demodulator. The
data is reconstructed in accordance with a predetermined
algorithm to present a graphic display 84 of pipe to soil
potential versus distance along pipeline.
The general circuit is shown in block form in Fig. 5.
The analog pipe-to-soil potential is received between unit input
25 ~ terminals 69 and is measured and simultaneously di~itised by the
digital voltmeter 86. The output 88 of the digital volt~eter is
read by the CMOS microprocessor ~MPU~ 90 and is displayed in
numeral form by the liquid crystal display (LCD) 92. If the
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surveyor decides to record the reading he presses an ~enter~ key
(E) on the keyboard 76 and the pipe-to-soil potential is stored
by the MPU 90 in an 8K internal random access memory (RAM) 92.
This process is continuously repeated for pipe-to-soil
measurements and for entering codes corresponding to
topographical locations along the route of the pipe as the
survey progresses. On completion of the survey the data is
copied from the 8R RAM to an external erasable programmable
read-only memory (EPROM) 94 under the control of the MPU 90 as
described in more detail hereinafter. After copying the data is
still present on the RAM 92. The data stored in the RAM 92 can
also be copied directly to remote locations using a modem 96
which enables the data to be transferred in serial form over
telephone lines to a computer 98 or a printer/plotter 100 in
which it is processed and analysed in accordance with
predetermined algorithms to provide a graphic output as shown in
Fig. 3. The structure and operation of the circuitry will now
be described in more detail with reference to Figs. 6, 7, 8
and 9. The unit 50 contains two printed circuit boards (not
shown) powered by a set of rechargeable 6 volt batteries. All
electronic components in these circuits are CMOS components to
draw as little power as possible from the batteries.
The first printed circuit board of which the circuit is
shown in Figs. 6 and 7 contains digital voltme~er and analog to
,
digital converter 102, the microprocessor unit MPU 90, the
EPROM~104 containing the program for the MPU 90, the 8 kilobyte
RAM 92, an address decoder 106, an address latch 108 and buffers
110 and 112.
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The A/D converter 102 is an ICL7109 produced by
Intersil or equivalent and transforms the analog pipe-to-soil
potential reading into a binary number which the MPU 90 can read
and process. The A/D convertex 102 is driven by a high
frequency crystal oscillator 114 which acts as the time base for
proper synchronisation of the circuit. The analog input 116 of
the A/D converter can receive three different analog inputs.
Terminals 69 form the main input and are used to receive the
pipe-to-soil potentials when performing surveys. The input 116
consists of a resistive voltage divider 118 and 120 which gives
a high impedance of 10 million ohms/unit, a high voltage
protector 122, and a noise filter in the form of a capacitor
124. The second input to the A/D converter 102 is parallel
with the first one through analog switch 126 that can be turned
on or ofE by transistor 128 and flip-flop 130. The MPU 90
sends information to the flip-flop 130 to turn transistor 128 on
or off which turns analog switch 126 on or off. When the
analog switch 126 is on, the positive 5 volts supply from the
batteries is connected through resistors 132 and 120 which acts
as a voltage divider to the input of the A/D converter 102P
This enables the positive battery supply to be checked to see if
it has to be recharged. The transistor 128 makes a voltage
level change so that the analog switch 126 can be turned on or
off by the MPU 90~ The flip-flop 130 retains the state ~on or
off) of the analog switch 126 until the change in response to a
control signa7 from the MPU 90O This is because the A/D
convertex 102 requires about 150 milliseconds to perform a
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conversion. During this time, the analog input must be stable
so that the MPU 90 can turn on until 32 readings have been
completed~ re~uiring four seconds of battery status display.
The third input of the A/D converter 102 is similar to the
second input except that it is used to reacl the negative 5 volts
supply. The electronic components used are analog switch 136
voltage divider resistors 134 and 120, transistor 138 and flip
flop 140. Analog switches 126, 136 are normally off so that the
first input to the A/D converter 102 is the pipe-to-soil
potential input r ~ia terminals 69. Capacitors 142 r 144 / 146 ~
resistors 148 and 150 act as components that detemine the speed
at which the A/D converter 102 will operate. Resistor 152 is
the precision adjustment for the A/D converter 102. The A/D
converter 102 performs seven conversions per second. Every time
one conversion is completed, the A/D converter 102 sends an end
of conversion signal which is stored in flip flop 154. The
output 156 of flip flop 154 is connected to an interrupt pin 160
of the ~PU 90 (Fig. 7). When the MPU 90 receives this interrupt
signal, it stops program execution and reads the binary signal
value for a potential value just transformed by the A/D converter
102. The binary value is read in two bytes and displayed on the
liquid crystal display section 78 of the unit S0. When reading
this value, the interrupt flip flop 154 is automatically reset
to its original state.
The A/~ converter 102 has a clock output 162 which goes
to flip flop 164 which divides the clock freauency by two. The
output 166 of the flip flop 164 is fed into the clock input 168
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of the MPU 90. A suitable MPU 90 is a NSC800 manufactured by
National Semiconductor and controls the operation of all the
tasks within the system, including reading programs from the
EPROM 104 (CMOS type 2716), and storing the pipe-to-soil
potential readings into the RAM 92 (HITACHI HM6264LP-15 ) . When
a program is being executed by MPU 90, addresses go to the
address decoder 106, the outputs of which are the eight
different device selection signals for: the EPROM 104, the
RAM 92, liquid crystal display 78 (Fig. 8) display (~ig. ~), the
keyboard 76 (Fig. 9), the A/D converter 102, the reading o the
battery status, 130, 140, the external port 74 and a spare. The
address decoder 106 is used to latch the eight addresses because
they are multiplexed with the data. The MPU 90 has a clock
output 162 which is the input frequency divided by two, this
output being used by the display unit 78 through connector 173.
The second circuit board as shown in Fig. 8 contains
the keyboard 76, the ei~ht digit liquid crystal display 78, and
associated electronics. This printed circuit board is connected
to the MPU 90 board through connector 172. The keyboard 76 is a
sixteen key sealed type 4 x 4 matrix keyboard and is connected
to a keyboard decoder/debouncer circuit 174 which performs all
debouncing and decoding of the keyboard 76 according to the two
timing capacitors 176 and 178. When a key is pressed and
properly debounced, a data available signal is passed to flip
flop 180 where it is stored and becomes an interrupt signal to
MPU 90. Once the MPU 90 receives this interrupt signal~it stvps
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execution of the current program, reads the keyboard 76 signal
and executes a different part of the program in accordance with
the keyboard signal. When the MPU 90 reads the keyboard 78
signal, the interrupt flip flop 180 is automatically resetO ~he
data coming from the keyboard decoder 174 is present on the four
least significant bits of the eight bit data bus~ in a
hexadecimal form. A connector 182 is provided to allow
connection of an external switch (not shown) so that the
surveyor can store information in the RAM 92 by pushing that
switch instead of usin~ the enter key (E) of the keyboard 76.
The display section consists of the li~uid crystal
display 78, two 32-bit display shift registers 183 and 184 and a
binary counter 186. The LCD 78 is driven by an a.c. frequency
of approximately 100 ~ertz, which is produced by dividing the
MPU gO clock output 162 by the divider 186, the division it
produces being this is appropriate to drive the LCD 78 in a.c.
mode. The output of the counter 186 is connected to the common
pin 188 of the LCD 78 and the polarity input pins 190 of the two
shift registers 182 and 184. The output of the shift register
182 is connected to the input of the shift register 184 so that
they simulate a 64 bit shift register. The LCD 78 used has
eight digits each having eight segments for a total of 64
different segments. The programs are responsible for sending
information to the display in serial form so that it can be read
by the surveyor. The MPU 90 accesses the LCD 78 by writing to
a specific location in the RAM 92. Bit 0 o~ the data bus
inst~ucts the shift registers 182 and 184 which segments of the
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LCD segments have to be turned on or off.
The external port 74 is used to connect any external
device to the main unit, such as the EPROM programmer 94 and the
Modem Interface 96~ The system uses both positive and negative
voltages, and as shown in Fig~ 6 the batteries are attached
through connectors 192 and 194. Diodes 196 and 198 are used to
drop the voltage of one battery from -6 to -5 volts. Diodes
200, 202 and 204 are used to drop the voltage of the other
battery from +6 to ~5 volts, Switch 206 is used to turn the
system on and off~ Diodes 208, 210 and 212 are used to provide
back up power to the RAM 92. Connector 214 is an optional
connector to provide the possibility of disconnecting the pos~er
supply going to the RAM 92. A switch (not shown) can be
connected to connector 214~ Normally the power supply to RAM 92
is never removed to retain the data in the memory, which lasts
up to 40 days before the supply is drained.
The EPROM Programmer 94 shown in Fig. 9 is a unit that
permits information to be stored in a permanent form extarnal to
the unit 50 in order that it can be easily copied to another
computer. The EPROM Programmer is completely controlled by the
main unit 50 and receives data through connector 74. It has an
address latch 216, an address decoder 218, an 8 bits data
buffer 220, an 8 bit data latch 222, an 8 bits data control
latch 224, a 12 bits binary counter 226, and voltage regulators
228 and 230~ This is a battery operated unit and it can program
type 2764 EPROMS. The address latch 216 is used to latch the
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multiplexed addresses coming from the Field Unit 50. These
addresses are then decoded by address decoder 218 with read and
write signals to give proper selection to the 4 different
registers or latches of ~he board 220, 222, 224 and 226. Lat~h
222 is used to store the data for programming into the EP~OM 94.
It is a three states output latch which is enabled or disabled
by one bit of the control latch 224. Data buffer 220 is an 8
bits three states data bus buffer used to read the content of
the EPROM 94 after it has been programmed and is used to verify
that the correct data was programmed in the EPROM 94. Counter
216 is a 12 bits binary counter which gives the addresses to the
EPROM 94 to be programmed. It can be cleared by one bit in the
control latch 224 or incremented by reading the control latch
224. Latch 224 is the control register and it controls
difEerent signals to perform programming. One of these is the
VPP signa} (positive potential) which must switch from 5 volts
to 21 volts to permit the data in the EPROM to be 'burned in'
when data is copied from the RAM 920 Integrated circuit 232
transistor 234 and voltage regulator 230 control this
operation. Resistor 238 is an adjustment potentiometer to
permit the value of 21 volts to be precisely set. Integrated
circuit 236 and transistor 238 control the turning on or off the
EPROM 94. A voltage regulator 228 supplies 5 volts to the
clrcuits. The EPROM 94 is inserted in a zero insertion force
socket (not shown).
The use of the apparatus will be described as follows
in relation to the schemstic disgrams, circuit diagrams and flow
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charts of operation o. various parts of the program to
facilitate bet~er understanding of the invention. When the unit
50 is switched on the system variables are initialised in
accordance with the steps illustrated in the program flow chart
of Fig. 10, all existin~ memorizing is cleared. The stack
pointer is initialised, the interrupts are enabled, when the key
is pressed, it sends an interrupt signal to MPU 92 which reads
the key and initialises the INTCLA sub-program which is executed
by microprocessor as shown in Fig. 11. This main program loop
is maintained until the microprocessor receives an interrupt
signal from the analog to digital converter 102 in the digital
voltmeter 86 or from another key being depressed on the keyboard
76.
A surveyor 52 walking along the route of a buried pipe
56 with the logging unit 50 connected as shown in ~ig. 1 will
see a potential displayed on the liquid crystal display 78 in
accordance with the INPOT sub-program as shown in Fig. 1~ every
time the reference Cu-CuSO4 electrode 62 makes contact ~ith
the ground 54. ~fter appropriate dis~ance intervals, say 10
meters, the surveyor 52 records the pipe-to-soil potentials
measured by pressing key (E) on the keyboard 76. The MPU 90
implements data storage in accordance with the enter flow chart
as shown in Fig~ 13 using the Flag 1 - 1 negative decision step
240 and or flag 0 = 1 negative decision step 242 if the RAM 92
i5 not full, data is entered into the RAM 92 and the system
returns to normal. The data is entered, osing key E, a ~Blink~
routine is executed, as shown in more detail in Fig. 14 which
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causes the LCD 78 to flash twice after which it indicates 'nor'
in LCD i.e. normal operator using the RET~OR flow chart as shown
in Fig. lS and the potential value is again displayed. The
surveyor repeats this at these intervals although it should be
understood that they do not have to be accurate; since the
computer uses the number of readings taken to compute an average
interval between two predetermined positions. This is adequate
for interpreting the results since if a problem arises due to
corrosion in one part of the pipe, a section oE pipe many meters
on each side of the suspected corrosion area will be
investigated in more detail. At any location where there is an
identifiable topographical feature such as a chainage marker,
bridge, road or foreign crossîng, i.e. another buried pipe
crossing the surveyed pipe the surveyor can identify this
location by entering the data in the form of a code using a
function key/ F. To do this he presses key F on the keyboard 78
and enters numerals corresponding to the feature in question.
For example, for a railroad crossing, a code C3000000 teight
digits) as shown by numeral 300 in Fig. 3. When the F key is
depressed, the MPU 92, in accordance with the INTCLA sub-program
(Fig. ll), if flag 7=0 is negative, checks if the function
is in an auxiliary command table (not shown) and if in the
affirmative the CODE sub-program t~ig. 16) is executed which
resets sets flags 0,1,3 and resets flag 4 to permit the code
display routine AFFCD tFig. 17) to be called. When the ~ key is
depres~ed after the F key the enter flow chart follows a
different path using the decision step flag 1 = 1 and the
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~slink~ (Fig. 14) is again executed as the code data is entered
into the RAM 92. As the survey progresses the surveyor
continually enters pipe-to-soil potentials and codes into the
~AM 92, up to a maximum equivalent to 4000 potentials. However,
each pipe-to-soil potential requires 2 bytes (2x8 bits) and each
code requires 3 bytes (3x8 bits). Therefore the higher the
ratio of codes to potential measure~ent the sooner the RAM 92 is
filled. The EPROM 104 contains a number of programs which can
be executed by the MPU 90 in response to user input signals via
the keyboard to provide a number of auxiliary functions.
For example, the' a~ount of available RAM 92 memory can
be checked at any time by invoking the MEMDIS sub-program as
shown in Fig. 18, and the amount of available memory will be
displayed to the surveyor in bits available potential readings,
on the LCD 78. The battery voltage level can also be checked by
executing the program shown in flow chart form in Fig. 19; after
execution of these programs, the MPU 90 and LCD 78 return to
normal, potential measuring mode. If a function i5 wrongly
entered then an error routine will be displayed on the LCD 78
using the AFFER routine as shown in flow chart form in Fig. 20
which in turn refers to sub-routines of AFFDEL, AFFI, DELX and
DEL50 shown in Figs. 21, 22, 23 and 176 respectively. Once the
error has been displayed, the MPU 90 returns the system to
normal after a short interval.
When the data is being entered using the ENTER program
of Fig. 13, if the RAM 92 is full a display message routine
AFFDEL (Fig. 20) is executed and segments of the LCD 7~ will be
- 22 -
:~2a..~76
driven to indicate 'Full'. The last entry stored in the RAM 92
can be recalled using the RECALL program flow chart shown in
Fig. 24 by pressing the respective key 'B' on the keyboard 76.
The recalled data can be entered using ~he ENT~R flow chart of
Fig. 13 or cancelled by executing the CANCE'L program shown in
flow chart form in Fig. 25.
When the survey is completed the data stored in the RAM
92 may be transferred to the erasable programmable read only
memory EPROM 94 or to a computer 98 via a modulator unit 76.
The EPROM circuit îs shown in Fig. 10 and has already been
described and is connected to the input socket 74 on the rear of
the unit 50 (see Fig. 4) by a connector. The data is then
transferred from the RAM 92 as described in accordance with a
DUMP/EPROM program executed by the MPU 90 which is shown in Fig.
26, ~fter the data has been transEerred from the RAM 92 to the
EPROM 94 as described above with reference to Fig. 10, the
buffer latch 218 is read and displayed as described above to
verify that the data has been transferred into the EPROM 94.
A~ter this occurs the MPU 90 executes the PRO7 subprogram (Fig.
27) to remove the signals to the EPRO~ g4 and switch off the
power to the EPROM 94 and return to the manual potential
measuring mode.
The data can also be transferred to the ~odem 96 with a
DUMP RS 232 program (FigO 28) which is executed by the MPU 90.
The data is transferred into ASCII serial form or transmission
over the telephone line 78 and is transmitted when the host
computer 80 is ready and after transmission the MPU 90 returns
- 23 -
74~;
the unit to the normal operation mode. The data is converted by
a modulator 76 as shown in Fig. 3 and after transmission is
demodulated. A host computer 98 will usually contain its own
demodulation unit but, if necessary a separate unit can be used.
When the data is received by the host computer 80 it is
processed in accordance with standard algorithms which decode
the signal and convert the stored potentia:L data and coded data
into signals which are displayed on the host computer. The
computer 80 prepares a graphic display of pipe-to-soil potential
on the ordinate (y-axis) against distance along pipeline which
is the abcissa (x-axis) in a format which facilitates clear
presentation of the data and facilitates interpretation by the
user.
Without departing from the scope of the invention it
should be understood that various modifications may be made to
the embodiment as hereinbefore described. For example the
apparatus can be used to measure potential diferences between
structures, for example between two crossing pipes or to measure
the voltage drop across shunts between a sacrificial anode and
the pipe, The logying apparatus could also be used in
conjunction with a timing device to assess the fact of stray
d.c. current of certain areas. The apparatus of ~ig, 9 need not
be used with only a battery supply being equally well adapted to
be powered from the electrical a.c. supply via a transformer.
The random access memory of unit 50 can be any size ~or example
16k or 32k or even larger and the data can be transmitted over
telephone line using any other suitable data transmission system
~ ~ .
,j - 24 -
such as EPISIDER. The information in the RAM can be transferred
directly to a computer or to a plotter and the results can be
presented in tabular form; in addition an algorithm can be used
to present only data within certain ranges for example, only
those potentials which exceed a certain value.
The results are evident that the circuitry of present
invention could incorporate a voice synthesizer to present to
the surveyor an audible indication of the operation of the
unit.
10It should also be understood that the liquid crystal
display in the keyboard may be incorporated into the handle of
the staff so that as the surveyor contacts the reference
electrode with the electrolytes or ground the potential is
displayed on the staff and by merely pressing a button on the
staff he can enter the data into solid state memory which in
such a case may be included in a unit located in the surveyors
pouch or in his pocket.
Advantages to the embodiment include the logging unit
: which is small, portable and is easily carried by a surveyor;
the data is entered into a solid state memory and is stored
there in a quasi permanent form since the batteries provide for
storage of the data in the memory or up to 40 days; the format
in which the data is stored facilitates its copying to
computers, printers and data transmission systems to facilitate
: 25 th~e processing and analysis of the recorded data; the apparatus
does not require additional equipment such as an odometer to
indicate distance measurement since distances entered are
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~ ~J~ 7 ~
approximate and are adjusted by the computer wh~n the data is
being processed; and the apparatus provides facilities to
correct error on entry. Consequently the apparatus considerably
speeds up the surveying process and analysis of the results so
that surveys of pipelines can be carried out more frequently.
:
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