201.940b-20 201.940z Calibration of dial setting versus attenuation difference for indirect- Special calibrations not included in the above schedule. **See 201.900(b). 201.941 Insertion loss measurements on fixed attenuators. (a) Insertion loss measurements are made on fixed two-port attenuators. (b) Insertion loss measurements are made for insertion loss values from 0 to 50 dB. This range of attenuation values can be extended to 70 dB in some frequency ranges. (c) Fixed attenuators should have a VSWR less than 1.1 at each waveguide port. Item Description Fee Measurement of insertion loss of fixed attenuator at a single frequency 201.950 Effective noise temperature measurements on noise sources. (a) Effective noise temperature measurements are made on waveguide noise sources (usually a gas-discharge tube) under conditions of continuous, unmodulated operation in the range 1000 to 300,000 °K (excess noise ratio range 3.8 to 30 dB). (b) The direct current required for normal operation of the gas-discharge tube should not exceed 300 mA but should be sufficient to prevent excessive plasma oscillations. (c) The waveguide noise source must have an input VSWR no greater than 1.2. (d) The gas-discharge tube should be secure in the mount, and the output port of the unit should be terminated with a matched load. Item 201.950a-1 201.950z **See 201.900(b). Item Measurement of effective noise temperature of noise source in WR90 (**) Special calibrations not covered by the above schedule___ (**) Description Measurement of effective noise temperature of noise source at a 202.201 Optical instruments 202.202 Photographic objectives 202.203 Optical components, spectacle lenses, goggle lenses, etc. 202.311 Photography (step table density, residual thiosulfate concentration, etc.) 202.406 Surveyors' measuring instruments (other than tapes) 202.623 202.624 202.625 Large mass standards Mass and Volume Calibration of mass elements of pressure-gage testing apparatus Recalibration of mass standards Glass volumetric apparatus 202.626 Metal volumetric apparatus 202.627 Hydrometers 202.628 Density determination of solids and liquids 202.103 Miscellaneous photometric measurements and tests. Item 202.103 a 202.103z Description Determination of luminous transmittance of neutral or colored filter, For special tests not covered by the above schedule, fees will be Rating tests on lamps. These are routine photometric rating tests Fee (*) Fee 202.104z For special tests not covered by the above schedule, fees will be *For current fees, see Appendix C. 202.105 Spectrophotometric standards. NOTE on item a. Transmittances of these disks at wavelengths from 365 to 390 nm (nanometer, 10-9 meter) and from 750 to 1,000 nm will also be determined on request in accordance with item c of fee schedule 202.105. Values will be obtained for a temperature of 25 °C. The effect of change of temperature has not been determined for these glasses outside the range from 390 to 750 nm. It is known, however, that for all four types of glass the temperature effects are very small from 750 to 1,000 nm, probably negligible for the usual room-temperature variations. On the other hand, temperature effects are always large for these kinds of glass when the transmittance as a function of wavelength is decreasing rapidly towards shorter wavelengths, so that increasingly large temperature effects may be expected for these filters in the ultraviolet. NOTE on items j and k. In the General Electric recording spectrophotometer the design is such that the radiant energy is incident in a slightly diverging beam whose axis is at 6° to the perpendicular to the surface. The specular component of the reflected energy is thus diverted away from the entrance aperture towards a port on the side. This port may be filled with MgO or with a black material, so that the specular component may be respectively "included" in, or (for plane surfaces) "excluded" from, the measurements. This is covered in items j and k. Only one Vitrolite working standard is needed for the measurement of spectral directional reflectance on the General Electric recording spectrophotometer. This calibrated Vitrolite standard and the samples to be tested are in turn placed at the sample aperture of the inte grating sphere, and any highly reflecting substance such as MgO or MgCO, may be used at the comparison aperture provided the material to be tested does not reflect more than the comparison material. The directional reflectances of the test samples relative to freshly prepared MgO are then obtained by multiplying (at the respective corrected wavelength) the values for these samples read from the curve sheet, by the ratios of (a) the standard Vitrolite values reported to (b) the values for the Vitrolite read from the curve sheet. Item Description Fee 202.105a Standards of spectral transmittance for checking the photometric Each disk Transmittance, 365 to 1,000 nm for standardization purposes. Sam- One sample at one wavelength_ (*) (*) 202.105b 202.105c Each additional wavelength on the same sample___ Didymium glass standards for checking the wavelength calibration of (*) 202.105d 400 to 750 nm, 10-nm slits, each standard__. 202.105e 730 to 1,080 nm, 20-nm slits, each standard... 202.105f 202.105g 202.105h For two calibrations on the same glass (items 202.105d and 202.105e), Holmium oxide glass standards for checking the ultraviolet and visible 240 to 370 nm, each standard 360 to 650 nm, each standard. See footnote at end of table. |