Title of Invention

"A DIGITAL CONCRETE RESISTIVITY LOGGER WITH PERSONAL COMPUTER (PC) INTERFACE"

Abstract

A digital concrete resistivity logger with personal computer interface which comprises a four probe assembly (3) consisting of four spring loaded conducting electrodes fixed in a row with equidistant interelectrode distance (G), characterised in that, the outer two electrodes of the said probe assembly (3) being connected to an alternating current source (1) through a voltage to current converter (2), the inner two electrodes of the said assembly (3) being connected to a programmable instrumentation amplifier (PI A) (4), the PI A (4) output being connected to a precision full wave rectifier (PFWR) (5), the rectified output of the said PFWR (5) being interfaced to a central processing unit (CPU) (8), of a microprocessor with a keyboard (KBRD) interface (10), through a 12-bit analog to digital converter (ADC) (6) and a programmable peripheral interface (PPI-1) (7), the said CPU (8) being provided with a conventional RS-232C interface (9) to a personal computer (pc) and an output display (13) through a programmable peripheral interface (PPI-2) (11) and display interface (12).

Full Text

This invention relates to a digital concrete resistivity logger with PC interface. The present invention particularly relates to the improvement in or relating to digital concrete resistivity logger with PC interface. The main usage of the device of the present invention is in the field of reinforced cement concrete (RCC) structures where the quality and condition of the concrete is very important. This logger measures the resistivity of the reinforced concrete giving valuable data to assess the corrosion in RCC structures. The instrument can also be used to measure the resistivity of other materials, which have a resistivity range of 100 Q cm to 2000 Kfi cm. Hitherto it has been proposed to measure the resistivity of concrete with digital meters [Ref. Non destructive testing of concrete by electrical resistivity measurement - N.S.Rengaswamy etal. "Indian Concrete Journal 1986"] as well as using microprocessor based resistivity logger (developed by M/s Colebrand Limited, England). The digital meters have the drawback in that there is no provision to store measured data and each value has to be manually recorded. In addition the sensor probes do not contain couplant reservoirs and the concrete surface has to be wetted manually for proper electrical contact before each measurement is made. On the other hand the available microprocessor based resistivity loggers suffer from the drawback, that they measure only the resistance and not the resistivity at the measuring site. To obtain the resistivity, the stored data from the logger has to be downloaded to a PC where software calculates and displays the resistivity. In addition, operation and maintenance of the available four-probe setup is cumbersome in that it is difficult to fill in and drain out the couplant from the probe reservoirs. The main object of the present invention is to provide a digital concrete resistivity logger with PC interface, which obviates the drawbacks as detailed above. Another object of the present invention is to provide a microprocessor based four-probe concrete resistivity logger with PC interface. Yet another object of the present invention is to develop a spring-loaded fourprobe system, each probe having a couplant reservoir, the filling in and draining out of the couplant solution from the probe system being simple and easy. Digital concrete resistivity logger with PC interface of the present invention is a new product useful to evaluate the concrete quality in RCC structures. It measures the resistivity of the reinforced concrete providing valuable data to assess the corrosion in the RCC structures. The instrument consists of two main parts, a measuring console and a four-probe sensor assembly. The console measures the resistivity and stores the data in its memory. It has the capacity to store ten thousand readings. The sensor assembly consists of four probes, each having a couplant reservoir. A constant current is impressed to the concrete with the two outer probes and the voltage drop, which is a measure of concrete resistivity, is sensed through the two inner probes. The console converts the signal into equivalent resistivity and stores the data in its memory. A software package has been developed to download the data to a personal computer through a RS-232 cable. Further analysis of data is possible using the software. Hard copies of the data files can be had on a printer. Figure 1 of the drawings accompanying this specification represents the block schematic of the digital concrete resistivity logger with PC interface of the present invention. It consists of an alternating current source (1), which is an oscillator generating sine wave of fixed frequency. The voltage to current converter (2) receives the signal from the oscillator and converts it into a constant current. The constant current thus derived is fed to outer two electrodes of a four-probe assembly (3). The four probe assembly consists of four conducting electrodes separated by a fixed distance and are arranged in a single row. The voltage developed across two inner electrodes of the assembly is fed to a programmable instrumentation amplifier (PIA) (4), the gain of which changes according to the input value. The output of the amplifier (4), which is an alternating signal, is converted to an unipolar voltage using a precision full wave rectifier (PFWR) (5). The rectified output, which is proportional to the concrete resistivity, is interfaced to the central processing unit (CPU) (8) of the microprocessor through a 12-bit analog to digital converter (ADC) (6) and a programmable peripheral interface (PPI) (7). RS - 232C interface (9) is used to download the stored data from the microprocessor memory to a personal computer. A set of functional keys accesses the CPU through a keyboard (KBRD) interface (10). The result from the CPU (8) is displayed on a single line 16 characters liquid crystal digital display (13) through a PPI (11) and a display interface (12). Figure 2 of the drawings accompanying this specification shows the schematic of an embodiment of the four-probe assembly of the present invention. It consists of four spring-loaded brass probes fixed to a PVC structure. Two PVC frames (14) are the main support of the probe assembly. The probe handle (15) is used to grip the assembly while measuring. Four brass probes with reservoirs (16) to hold the couplant are firmly fixed to two guiding frames (20) made of PVC. At the top of each probe there is a threaded cap (17) used to fill the couplant in to the reservoir. The probes are fixed in a row and each probe is fixed in such a way that the tips (18) are exactly at a distance (G) of 25mm from each other. This distance is critical and has direct influence on the accuracy of measurement. The socket (19) fixed to one of the frames (14) is used to connect the probe assembly to the main instrument dttrj*^ measurement. The electrical connection of each probe is independently brought to the socket (19) by individual wires. The dotted line in figure 2 indicates the layout of the connecting cables. Figure 3 of the drawings accompanying this specification represents the front panel configuration of the digital concrete resistivity logger. It consists of 16 characters, single line LCD array (display) to display the resistivity value. On left side of the panel there is a switch (PWR) to power the instrument, a fuse for protection and a jewel lamp (ON) to indicate that the instrument is switched on. A connector (BAT) is also provided to operate the logger with 12V battery. On right side of the panel a socket (SENSOR) has been provided to connect the four-probe assembly to the resistivity logger. Another socket (RS 232C) connects the logger to a personal computer. In addition there are 11 keypads the functions of which are detailed below. On pressing this key the instrument displays the sign on message and the instrument returns to the measurement mode. On pressing this key the logger measures, displays and stores the resistivity value in the RAM. After taking ten readings in a column, pressing this key increments the column number by one, indicating that the next reading will be the first in the next column. Pressing this key displays the stored resistivity value of the previous survey location. Pressing this key displays the stored resistivity value of the next survey location. Pressing this key, stores a marker in memory, which indicates the end of a block of measurements. If the value of any location is not to be recorded, pressing this key will store a star (*) mark in the memory. Pressing this key transmits the data from logger memory to PC through the serial port. On pressing this key logger will display press INSERT key message. Pressing this key (proceeded by CLR key), instrument clears all data from the logger memory and resets the file count to zero. OEL This key is used to delete the last reading stored in the memory. The present invention relates to improvement in or relating to development of a digital concrete resistivity logger with PC interface which comprises of a spring loaded four probe assembly, electronic hardware and software to calculate, store and display directly the resistivity of concrete, a set of key pad functions to operate and interact with the logger, an interface to directly display the data on a single line 16 characters LCD display, a RS - 232C interface to transfer the data from the logger to a PC, supporting communication package to analyze the downloaded data and a hardware interface to operate the logger with a 12 V battery at the measuring site. Accordingly the present invention provides a digital concrete resistivity logger with personal computer interface which comprises a four probe assembly (3) consisting of four spring loaded conducting electrodes fixed in a row with equidistant interelectrode distance (G), characterised in that, the outer two electrodes of the said probe assembly (3) being connected to an alternating current source (1) through a voltage to current converter (2), the inner two electrodes of the said assembly (3) being connected to a programmable instrumentation amplifier (PIA) (4), the PIA (4) output being connected to a precision full wave rectifier (PFWR) (5), the rectified output of the said PFWR (5) being interfaced to a central processing unit (CPU) (8), of a microprocessor with a keyboard (KBRD) interface (10), through a 12-bit analog to digital converter (ADC) (6) and a programmable peripheral interface (PPI-1) (7), the said CPU (8) being provided with a conventional RS-232C interface (9) to a personal computer (pc) and an output display (13) through a programmable peripheral interface (PPI-2) (11) and display interface (12). In an embodiment of the present invention, each of the probes of the springloaded four-probe assembly is provided with a wetting agent (couplant) filled reservoir (16) with open ably fixed top cap (17) and bottom probe tip (18) capable of providing electrical contact between the probe(s) and concrete surface during measurement. In another embodiment of the present invention the alternating current source (1) is an oscillator generating sine wave of fixed frequency. In yet another embodiment of the present invention the voltage to current converter (2) is capable of receiving signal from an oscillator and converting it into a constant current. In still another embodiment of the present invention the logger has memory space to store readings of the order of 10,000. In still yet another embodiment of the present invention the microprocessor is provided with software capable of calculating, storing and directly displaying resistivity values. In a further embodiment of the present invention the keyboard (KBRD) interface (10) of the microprocessor is provided with an interactive keypad capable of operating and interacting with the CPU (8) to store, recall, delete and transfer data. In another embodiment of the present invention the hardware is powered by 12 V battery or equivalent power source. Following paragraph gives details on process steps to be followed while using the digital concrete resistivity logger with PC interface. Before using the resistivity logger the internal RAM storage battery should be charged by connecting the instrument to the mains power of 230V, 50Hz. The couplant reservoirs of the four-probe assembly should be filled with the wetting agent with a syringe. The performance of the logger should be tested using the calibration block supplied with the instrument. The calibration block consists of three equal resistances connected in series and the terminals are brought out for connecting it to the logger. To test the logger the calibration block is connected to the logger through the SENSOR socket and the instrument is switched on. On pressing the READ key the instrument has to display the value 100 KQ-cm. Four-probe assembly is connected to the logger with a 4-core cable. The concrete area to be evaluated is divided in to blocks of 10 rows and 10 columns so that each block will have 100 measuring points. Pressing the four-probe assembly setup gently on the surface ejects small amount of couplant from each probe establishing a good electrical contact between the probe and concrete surface. 'READ' key is pressed for every measurement. This displays the resistivity value and stores it in RAM. Measurements are made from the top left hand corner of the block proceeding vertically downwards till end of the column. 'EOC' key is pressed to proceed to the next column. This procedure is repeated for each remaining column and at the end 'EOF1 key is pressed to complete the measurement in the block. The procedure is repeated on other areas. After completing the readings at the site, they can be downloaded to a personal computer (PC) using the RS - 232 cable and supporting software. On transfer, the data can be viewed on the terminal along with the file numbers. The hard copy of the readings can be had on a printer. Further analysis of the data is possible using the software developed for the purpose. Digital resistivity meter of the present invention is a portable instrument that measures directly resistivity of concrete at the measuring site. The value is simultaneously stored in the memory. The four probes of sensor assembly have built in couplant reservoirs to establish good electrical contact between metal probes and the concrete surface while measuring. Filling in or draining out of the couplant from the probe reservoirs is very simple. Digital resistivity meters available in market do not have the provision to store the values. They do not have the couplant reservoirs and the concrete surface has to be wetted manually before each measurement is made. Microprocessor based resistivity logger available in the market measures only the resistance at the measuring site. To obtain resistivity, the stored data from the logger has to be downloaded to a PC where software calculates and displays the resistivity. In addition, operation and maintenance of the available four probe setup is cumbersome in that it is difficult to fill in and drain out the couplant where filling guns and draining blocks are to be used. Present invention avoids these cumbersome procedures. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. Measurements were made on concrete slabs of size 2.5' x 2.5' under different conditions. Following steps were followed for making measurements on different concrete blocks. 1. By connecting instrument to 230 volts supply the internal RAM battery was charged. 2. The reservoir of each probe was filled with couplant solution using syringe and the four-probe assembly was connected to the logger. 3. The logger was switched on. 4. Calibration of the logger was checked using the calibration block. 5. The concrete slab to be evaluated was divided in to five rows and five columns to obtain 25 test areas. 6. Four probes were gently pressed on each test area to automatically store the resistivity values in logger memory. Example 1 Resistivity measurements on concrete slab without cathodic protection and without chloride contamination. File name: fpr.O Resistivity in KQ-cm. (Table Removed) Results show high resistivity values indicating the un-contaminated concrete. The concrete is also chloride free as it is reflected by high resistivity values. Example 2 Measurement of resistivity on concrete slab without cathodic protection and with 3% chloride contamination. File name: fpr.1 Resistivity in KQ-cm. (Table Removed) Highest value = 75.2 KQ-cm Lowest value = 41.0 KQ-cm It can be seen that the resistivity values are less than 55KQ-cm in majority of points indicating the chloride-contaminated condition of concrete. Example 3 Measurement of resistivity on concrete slab with cathodic protection and with 1 to 3% chloride contamination. File name: fpr.2 Resistivity in KQ-cm. (Table Removed) Highest value = 93.2 KQ-cm Lowest value = 19.0 KQ-cm The resistivity is low in higher chloride contaminated areas and comparatively high at low chloride contaminated areas. Example 4 Measurement of resistivity on concrete slab without cathodic protection and with 1% chloride contamination. File name: fpr.3 Resistivity in KQ-cm. (Table Removed) Highest value = 152.8 KQ-cm Lowest value = 27.3 KQ-cm Rows 0 & 4 show lower resistivity values indicating chloride contamination. Rows 1, 2, & 3 reflect the conditions of chloride free concrete having high resistivity values. The main advantages of the present invention are: 1. The logger directly displays the resistivity of the concrete. 2. Logger is portable and can be operated with a 12V battery. 3. The four-probe assembly is simple and it is very easy to fill in the couplant and drain it from the reservoirs. 4. The stored readings with file numbers can be downloaded to a personal computer (PC) for further analysis. 5. Data can be analyzed by exporting the data file to Microsoft EXCEL, LOTUS or ORIGIN. 6. Resistivity distribution studies with respect to the distance from a reference point on the measured area are possible after downloading the data to a PC. We claim: 1. A digital concrete resistivity logger with personal computer interface which comprises a four probe assembly (3) consisting of four spring loaded conducting electrodes fixed in a row with equidistant interelectrode distance (G), characterised in that, the outer two electrodes of the said probe assembly (3) being connected to an alternating current source (1) through a voltage to current converter (2), the inner two electrodes of the said assembly (3) being connected to a programmable instrumentation amplifier (PIA) (4), the PIA (4) output being connected to a precision full wave rectifier (PFWR) (5), the rectified output of the said PFWR (5) being interfaced to a central processing unit (CPU) (8), of a microprocessor with a keyboard (KBRD) interface (10), through a 12-bit analog to digital converter (ADC) (6) and a programmable peripheral interface (PPI-1) (7), the said CPU (8) being provided with a conventional RS-232C interface (9) to a personal computer (pc) and an output display (13) through a programmable peripheral interface (PPI-2) (11) and display interface (12). 2. A resistivity logger as claimed in claim 1, wherein each of the probes of the spring-loaded four-probe assembly is provided with a wetting agent (couplant) filled reservoir (16) with open ably fixed top cap (17) and bottom probe tip (18) capable of providing electrical contact between the probe (s) and concrete surface during measurement. 3. A resistivity logger as claimed in claim 1-2, wherein the alternating current source (1) is an oscillator generating sine wave of fixed frequency. 4. A resistivity logger as claimed in claim 1-4, wherein the logger has memory space to store readings of the order of 10,000. 5. A resistivity logger as claimed in claim 1-6, wherein the keyboard interface (10) of the microprocessor is provided with interactive keypad capable of operating and interacting with the CPU (8) to store, recall, delete and transfer data. 6. A resistivity logger as claimed in claim 1-7, wherein the hardware is powered by 12 V battery or equivalent power source. 7. A digital concrete resistivity logger with personal computer interface, substantially as herein described with reference to the examples and drawings accompanying this specification.

Documents:

698-DEL-2002-Abstract-(21-08-2008).pdf

698-del-2002-abstract.pdf

698-DEL-2002-Claims-(21-08-2008).pdf

698-del-2002-claims.pdf

698-DEL-2002-Correspondence-Others-(21-08-2008).pdf

698-del-2002-correspondence-others.pdf

698-del-2002-correspondence-po.pdf

698-del-2002-description (complete)-21-08-2008.pdf

698-del-2002-description (complete).pdf

698-del-2002-drawings.pdf

698-DEL-2002-Form-1-(21-08-2008).pdf

698-del-2002-form-1.pdf

698-del-2002-form-18.pdf

698-DEL-2002-Form-2-(21-08-2008).pdf

698-del-2002-form-2.pdf

698-DEL-2002-Form-3-(21-08-2008).pdf

698-del-2002-form-3.pdf