Bryan C. Waltrip
Administration and Logistics
Please contact the administration and logistics staff before shipping instruments or standards to the address listed below.
Sinusoidal Phase Measurements
NIST will perform special-test phase angle measurements on phase angle generators, quadrature detectors, and phase bridge-networks. Restrictions apply, and technical limitations and arrangements for these tests should be discussed with NIST; prior arrangements are essential.
The NIST Special Tests for VOR (Very-high-frequency Omnidirectional Range) air navigation signals are described in detail in VOR Calibration Service, NBS Technical Note 1069 (see references). Two services are offered to support the calibration of VOR phase meters and generators. NIST has designed and built a standard VOR audio generator, used to calibrate unknown VOR phase meters, and a standard VOR phase meter, used to calibrate unknown audio generators. Direct generation or measurement of standard VOR rf signals are not a part of the service.
NIST has a capability for characterizing audio frequency phase meters over a frequency range of 2 Hz to 50 kHz. The standard used is a microcomputer-based system that synthesizes two sinusoidal voltages by means of digital techniques. The two signals are displaced relative to one another by a precisely known phase angle. Phase angles can be set with a resolution of 0.002 ° up to 5 kHz and 0.005 ° above 5 kHz. The amplitude of the two output signals can be varied independently from 0.5 V to 100 V rms. At power frequencies, one of the signals can be a current from 0.5 A to 5 A. The expanded uncertainty in setting the standard is less than 0.01 ° below 5 kHz and increases to 0.04 ° at 50 kHz if the two output signals have the same amplitude. For unequal amplitudes, this uncertainty increases to 0.015 ° and 0.09 ° respectively, if the amplitude ratio is less than 10:1. Measurements at amplitude ratios up to 100:1 are performed as Special Tests.
Although the accuracy of the phase angle standard does not rely on the stability of the frequency, the generated output, which can be varied in steps of 1 Hz, is locked to a crystal-controlled frequency synthesizer.
Special requirements for this service are as follows:
A. The voltage inputs of the phase meter to be tested must have impedances such that the current is limited to a few milliamperes at any applied voltage requested. Current inputs must have impedances low enough so that the compliance voltage does not exceed 2 V.
B. NIST will test the instrument in the as-received condition, without making adjustments other than those normally required for testing. Meters that are not in operating condition upon receipt at NIST will be returned to the owner.
C. In some cases, the response of phase meters involves significant time constants; in these cases, readings will be taken 30 s after the setting of the standard.
D. For given voltage and frequency settings, at least three readings will be taken at each specified phase angle. The order of readings will be randomized.
E. The experimental data are fitted to a mathematical model from which the phase meter response can be predicted. From the closeness of fit to the model, it can be determined whether observed deviations from the predicted values are significant.
F. Each phase meter will be operated under power for at least 2 h before test data are taken.
G. Meters that are not in operating condition upon receipt at NIST will be returned to the owner without repairs.
A 100 Ampere, 100 kHz Transconductance Amplifier, O. B. Laug, IEEE Trans. Instrum. Meas 45(3), 440-444 (June 1996).
Characterized Generator Extends Phase Meter Calibrations from 50 kHz to 20 MHz, N. M. Oldham and P. S. Hetrick, IEEE Trans. Instrum. Meas. 42 (2), 311-313 (Apr. 1993).
The NIST Sampling System for the Calibration of Phase Angle Generators from 1 Hz to 100 kHz, B. C. Waltrip, M. E. Parker, N. M. Oldham, and B. A. Bell, Proc. 1992 NCSL Workshop and Symp., 613-616 (July 1992).
NBS Measurement Services: Phase Angle Calibration Services, R. S. Turgel, J. M. Mulrow, and D. F. Vecchia, Natl. Bur. Stand. (U.S.), Spec. Publ. 250-26 (May 1988).
Phase Meter Calibrations at NBS, R. S. Turgel, J. Res. Natl. Bur. Stand. (U.S.), 93 (1), 53-59 (Jan. 1988).
Precision Calibration of Phase Meters, R. S. Turgel and D. F. Vecchia, IEEE Trans. Instrum. Meas. 36 (4), 915-922 (Dec. 1987).
NBS 50-kHz Phase Angle Calibration Standard, R. S. Turgel, Natl. Bur. Stand. (U.S.), Tech. Note 1220 (Apr. 1986).
A Wideband Transconductance Amplifier for Current Calibrations, O. B. Laug, IEEE Trans. Instrum. Meas. 34 (4), 639-643 (Dec. 1985).
A Precision Phase Angle Calibration Standard for Frequencies Up to 50 kHz, R. S. Turgel, IEEE Trans. Instrum. Meas. 34 (4), 509-516 (Dec. 1985).
NBS Phase Angle Calibration Standard, R. S. Turgel, N. M. Oldham, G. N. Stenbakken, and T. H. Kibalo, Natl. Bur. Stand. (U.S.), Tech. Note 1144 (July 1981).
A High-Performance Phase-Sensitive Detector, L. A. Marzetta, IEEE Trans. Instrum. Meas. 27 (4), 460-464 (Dec. 1978).
High-Precision Audio-Frequency Phase Calibration Standard, R. S. Turgel and N. M. Oldham, IEEE Trans. Instrum. Meas. 27 (4), 460-464 (Dec. 1978).
VOR Calibration Services, N. T. Larsen, D. F. Vecchia, and G. R. Sugar, Natl. Bur. Stand. (U.S.), Tech. Note 1069 (April 1985).
Fourier Transformation of the Nonlinear VOR Model to Approximate Linear Form, D. F. Vecchia, Natl. Bur. Stand. (U.S.), Tech. Note 1021 (June 1980).
A Wide-Range Current Comparator System for Calibrating Current Transformers, T. M. Souders, IEEE Trans. Power Appar. Syst. 90 (1), 318 (Jan.-Feb. 1971).Calibrations Phone: 301-975-2200, Fax: 301-975-2950 NIST, 100 Bureau Drive, Stop 8363, Gaithersburg, MD 20899-8363