The Code of Federal Regulations of the United States of America

take them except by special arrangement. Apparatus not in good condition will not be calibrated. If defects are found after calibration has begun, the effort may be terminated, a report issued summarizing such information as has been found, and a fee charged in accordance with the amount of work done.

(b) The customer should pack apparatus sent to NBS so as to minimize the likelihood of damage in shipment and handling. Suggestions on packing and shipping are made in some sections of SP 250. In every case, the sender should consider the nature of the apparatus, pack it accordingly, and clearly label shipments containing fragile instruments or materials, such as glass and the like. The use of "security express" should be considered in shipping delicate instruments.

(c) To minimize damage during shipment resulting from inadequate packing, the use of strong reusable containers is recommended. As an aid in preventing loss of such containers, the customer's name should be legibly and permanently marked on the outside. In order to prolong the container's use, the notation "REUSABLE CONTAINER, DO NOT DESTROY" should be marked on the outside.

(d) Shipping and insurance coverage instructions should be clearly and legibly shown on the purchase order for the calibration or test. The customer must pay shipping charges to and from NBS; shipments from NBS will be made collect. The method of return transportation should be stated, and it is recommended that return shipments be insured, since NBS will not assume liability for their loss or damage. For long-distance shipping it is found that air express and air freight provide an advantage in reduction of time in transit. If return shipment by parcel post is requested or is a suitable mode of transportation, shipments will be prepaid by NBS, but without covering insurance. When no shipping or insurance instructions are furnished, return shipment will be made by common carrier collect, but uninsured.

(e) NBS will not be responsible for the risk of loss or damage to any item during shipment to or from the Bureau. Any arrangements for insurance covering this risk must be made by the customer. Return shipment will be made by the Bureau as indicated in paragraph (d) of this section. The purchase order should always show the value of the

equipment, and if transit insurance is carried by the customer, this fact should be stated.

(f) The risk of loss or damage in handling or testing of any item by NBS must be assumed by the customer, except when it is determined by the Bureau that such loss or damage was occasioned solely by the negligence of Bureau personnel.

(g) When a test number has been assigned prior to shipment to NBS, this number should be clearly marked on the shipping container. When a test number has not been assigned, an invoice, copy of the purchase order, or letter should be enclosed in the shipment to insure proper identification. The original purchase order should be forwarded as appropriate to:

Test Administration Unit, National Bureau of Standards, Washington, D.C. 20234. or to

Coordinator, Calibration Services, Radio Standards Laboratory, National Bureau of Standards, Boulder, Colo. 80302.

(h) The calibrations listed in SP 250 are performed at these locations: Boulder, Colo., Gaithersburg, Md., and Washington, D.C.

(1) Calibrations of electrical standards and materials in the radio frequency region (above 30 kHz) and all frequency and time calibrations are performed at Boulder, Colo., and shipments should be addressed to:

Coordinator, Calibration Services, Radio Standards Laboratory, National Bureau of Standards, Boulder, Colo. 80302.

If apparatus for radio frequency is also to be given incidental low-frequency calibration (below 30 kHz), this may be done at Boulder, but if a complete range of low-frequency calibrations are needed, the instrument should be sent to: National Bureau of Standards, Route 708 and Quince Orchard Rd., Gaithersburg, Md. 20706.

(2) Calibrations listed in SP 250 other than those noted in paragraph (1) above, of this section, are performed in the Bureau's laboratories at either Gaithersburg, Md., or Washington, D.C. For shipments which are heavy (in excess of 100 lbs.) or bulky (a combined girth in excess of 27 cu. ft.), request a shipping address from:

Test Administration Unit, National Bureau of Standards, Washington, D.C. 20234.

Schedule work assignments for callbrations and other tests will generally be made in the order in which confirmed requests are received. However, Government work may be given priority. On the regular services, the workload is usually such that the turn-around interval, between the date a customer's apparatus is received and the date it is prepared for return shipment, will be not more than 45 days. Some types of instruments may require considerably longer, particularly if their abnormal behavior requires reruns to check reliability. Others can be calibrated and returned within 10 days. Special tests, such as the "z" items listed in SP 250 require individual scheduling. The customer who can spare his instrument for only a short time can usually arrange by letter or phone call for shipping it to the Bureau just as his assigned starting date approaches. A notice will be sent acknowledging receipt of the customer's standard and/or purchase order. If both a confirmed purchase order (or equivalent) and the apparatus have been received, estimates of a completion date and a calibration fee will be sent upon request.

[32 F.R. 21012, Dec. 29, 1967, as amended at 33 F.R. 10627, July 26, 1968]

§ 200.112 Witnessing of operations.

The Bureau welcomes scientists and engineers who may wish to visit its laboratories and discuss its methods. Ordinarily visitors will not be permitted to witness the actual carrying out of highly precise measurements because their presence introduces distraction that may lead to errors or delays. This policy may be waived in those cases where the visitor can be of service in setting up apparatus of a new or unusual nature, in the case of referee tests, or in other cases in which the legal validity of the result may require the presence of duly authorized witnesses.

(a) Results of calibrations and other tests are issued to the customer as formal reports entitled, "National Bureau of Standards Report of Calibration," "National Bureau of Standards Report of Test," or "National Bureau of Standards Report of Analysis," as appropriate. Copies are not supplied to other parties. Whenever formal certification is required by law, or to meet special conditions adjudged by the National Bureau of Standards to warrant it, a letter will be provided certifying that the particular item was received and calibrated or tested, and identifying the report containing the results.

(b) NBS reports of calibration generally include in sentence form a statement of the uncertainty attached to the numerical values reported. Limits of uncertainty usually comprise (1) an estimate of systematic error, plus (ii) a value of imprecision.

(1) Often the systematic error estimate is based on experience or judgment. Sometimes it is an explicit combination of a number of elemental systematic errors. Sometimes the value can be checked by using two completely different physical phenomena, types of standard, or measurement techniques.

(2) Imprecision is preferably expressed as three times the standard deviation of a single determination, or three times the standard error of the arithmetic mean of n determinations, either being a canonical value for the measurement process based on considerable recent experience. When extended experience is lacking, the terms "computed standard deviation" or "computed standard error" should be used.

(3) A laboratory using NBS results to estimate the uncertainty attached to its own work may equate its own systematic error to the NBS quoted limit of uncertainty, as a minimum. The imprecision of its own work is best evaluated by calibration records extended over considerable periods of time, with repetition of its specified calibration procedure and assurance that its measurement process is in statistical control. For further information see:

(i) Youden, W. J., Uncertainties in Calibration. IRE Trans., vol. I-11, Nos. 3 and 4, p. 133 (December 1962).

(ii) Eisenhart, Churchill, Realistic Evaluation of the Precision and Accu

take them except by special arrangement. Apparatus not in good condition will not be calibrated. If defects are found after calibration has begun, the effort may be terminated, a report issued summarizing such information as has been found, and a fee charged in accordance with the amount of work done.

(b) The customer should pack apparatus sent to NBS so as to minimize the likelihood of damage in shipment and handling. Suggestions on packing and shipping are made in some sections of SP 250. In every case, the sender should consider the nature of the apparatus, pack it accordingly, and clearly label shipments containing fragile instruments or materials, such as glass and the like. The use of "security express" should be considered in shipping delicate instruments.

(c) To minimize damage during shipment resulting from inadequate packing, the use of strong reusable containers is recommended. As an aid in preventing loss of such containers, the customer's name should be legibly and permanently marked on the outside. In order to prolong the container's use, the notation “REUSABLE CONTAINER, DO NOT DESTROY" should be marked on the outside.