201.940b-20

201.940z

Calibration of dial setting versus attenuation difference for indirect-
reading variable attenuator at each prescribed attenuation differ-
ence value additional to the initial attenuation difference value at
the same frequency and on the same attenuator as 201.940b-1 to
201.940b-8_.

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
of the following waveguide sizes terminated with standard wave-
guide connectors:

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
waveguide at a single frequency selected from 9.0, 9.8, and 11.2
GHz (Gc/s) -

(**)

Special calibrations not covered by the above schedule___

(**)

Description

Measurement of effective noise temperature of noise source at a
single frequency of the following waveguide sizes terminated with
standard waveguide connectors:

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,
one sample..

For special tests not covered by the above schedule, fees will be
charged dependent upon the nature of the test..

Rating tests on lamps. These are routine photometric rating tests
of the type made initially on lamps to be life-tested, the same
standards and equipment being used. The purpose of these tests
is to afford a quick check of the photometric values assigned to
lamps by various lamp life-test laboratories.

Fee

(*)

Fee

202.104z

For special tests not covered by the above schedule, fees will be
charged dependent upon the nature of the test_ _.

*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
scale of spectrophotometers; these consist of polished disks of glass,
2 to 3 mm thick and 30 mm in diameter, designated as cobalt blue,
copper green, carbon yellow, and selenium orange (copper green
filter also available in 25 mm square size); report includes (1) values
of transmittance at 25 °C at certain wavelengths from 390 to 750
nm, (2) estimated uncertainty of each value, (3) effect of tempera-
ture change on transmittance at each wavelength:

Each disk

Transmittance, 365 to 1,000 nm for standardization purposes. Sam-
ples submitted must be in good optical condition. Measurements
at room temperature. (If the sample is a disk 29.7±0.2 mm in
diameter, the measurements can be made at a specified tempera-
ture):

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
General Electric recording spectrophotometers; these consist of
Corning 5120 glass, 2 x 2 in., 3.0 mm thick, polished; report in-
cludes table of wavelengths of minimum transmittance:

(*)

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),
each standard...

Holmium oxide glass standards for checking the ultraviolet and visible
wavelength calibrations of recording spectrophotometers with
slit width less than 2 nm; these consist of Corning 3130 glass 2 x 2
in., 2.5 mm thick, polished; report includes table of wavelengths
of minimum transmittance:

240 to 370 nm, each standard

360 to 650 nm, each standard.

See footnote at end of table.