New forms of instruments for showing the presence and amount of combustible gas in the air . al plane parallel to each other and cm apart in arectangular case cm high, the top and bottom of which wereopen, so that the wires were freely exposed to the surroundingatmosphere. A Weston miniature voltmeter having 3 and 15volt ranges, with resistances of 220 and 1100 ohms, respectively,was used as the indicating instrument. By adjusting one wire the bridge was balanced. The detectorbridge was then placed in a box supplied with a steady stream ofair containing, in any experiment, a constant
New forms of instruments for showing the presence and amount of combustible gas in the air . al plane parallel to each other and cm apart in arectangular case cm high, the top and bottom of which wereopen, so that the wires were freely exposed to the surroundingatmosphere. A Weston miniature voltmeter having 3 and 15volt ranges, with resistances of 220 and 1100 ohms, respectively,was used as the indicating instrument. By adjusting one wire the bridge was balanced. The detectorbridge was then placed in a box supplied with a steady stream ofair containing, in any experiment, a constant and known percent-age of hydrogen. Fig. 12 shows how the reading changes withchange in the percentage of hydrogen in the air entering the is observed that concentrations as low as per cent give anindication, and that the proportionality between reading andpercentage falls off only slightly at the higher percentages. The effect upon the readings of protecting the instrument withdouble gauzes and baffle plates is also shown. The gauzes com- Bulletin Bureau of Standards, Vol. 15. Fig. 13.—Indicator B with connections Weaver!Weibel] Combustible Gas Detectors 73 pletely covered the openings at the top and bottom of the rectangu-lar case and the baffle plates were parallel to these and cm out-side. The gauze was of iron wire cm ( inch) in diame-ter with 11 meshes per cm (28 meshes per inch). The reading of this instrument for a given percentage was foundto be practically proportional to the total current, which is inaccordance with the theory of the compensated bridge in whichthe two coefficients, C, are equal. This indicator was also tried out with carbon monoxide andwith illuminating gas. The indications for any percentage of / +s 3r ^ <££^^ Of £345-6 CONCENTRATION OF HYDROGEN (PER CENT) Fig. 12.—Calibration curves for indicator A • carbon monoxide was found to be about one-half that for thesame percentage of hydrogen, while illuminating gas
Size: 1925px × 1299px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1900, bookdecade1910, bookidnewformsofinstru15unse
