18-08-2014, 12:09 PM
This method requires special temp. conditions & also provides error because the water rise in fabric strip is not easily detected by our eyes. But our model doesn\'t require any special condition & it give automatic reading on display due to visual indication there is no possibility of error.
This method requires special temp. conditions & also provides error because the water rise in fabric strip is not easily detected by our eyes. But our model doesn\'t require any special condition & it give automatic reading on display due to visual indication there is no possibility of error.
Our ckt consists of two identical ckt which consists of resistive wheatstones bridge, transistansed amp, Op-amp as a buffer, this part of ckt requires +12,0,-12 V DC power supply which is given through 7812. One the arm of each wheatstone bridge is formed by specific length of fabric strip which is to be tested. We use variable resistance for adjustment & calibration. Our ckt also consist of NAND-latch& IC 74C926 which include 4-digit counter & 7 segment display driver. A stable multivibrator is used to provide 1 Hz clock. This meter records vertical wicking height of test sample by using three needle like sensors. It displays absorption rate in seconds for 1 cm of wicking height.
Our project is based on electrical resistance principle. As water is excellent conductor of electricity conductivity. As soon as the fabric strip absorbs the water its conductivity increases due to moisture absorption. This ckt gies high sensitivity towords the test & doesn’t requires antinuous monitoring.