1 - PD High Range Mass Comparator 24M-265A-MA.pdf

24M-265A-MA

30 March 2023

Revision 0

PURCHASE DESCRIPTION

FOR

High Range Mass Comparator

1.0 SCOPE: This purchase description specifies a High Range Mass Comparator to be used in the calibration of mass standards by selected Precision Measurement Equipment Laboratories (PMELs) to calibrate both Avoirdupois and Metric field masses and torque calibration mass sets in the range of 2 to 23 kilograms.

2.0 PERFORMANCE REQUIREMENTS:

2.1 Display Resolution: The Mass Comparator shall be readable to at least 1 milligram.

2.2 Measuring Range: The Mass Comparator shall have a continuous metric range, which covers 2 kilograms to 23 kilograms minimum.

2.3 Repeatability: The repeatability of the Mass Comparator shall not exceed 4 milligrams throughout the Measuring Range (see PD paragraph 2.2 above).

2.3.1 Repeatability Definition: Repeatability for this instrument is defined as the standard deviation of 6 sets of 2 pairs of differences between two master weights of the same nominal value (6 runs using ABBA method).

2.4 Shift Test/Eccentricity: The Shift Test error of the Mass Comparator shall not exceed 50 milligrams throughout the Measuring Range (see PD paragraph 2.2 above).

2.5 Reliability: The Mass Comparator shall maintain its specifications over a period of 12 months, minimum.

2.6 Stabilization Time: The stabilization time for an individual reading shall be no more than 20 seconds.

2.7 Warm-up/Exercise: The Mass Comparator shall be able to perform measurements after 3 exercise cycles.

3.0 FUNCTIONAL REQUIREMENTS:

3.1 Manual Control: The Mass Comparator shall be self-contained and manually controlled via push button(s) or switch.

3.2 Internal/External Adjustment: The Mass Comparator shall have an internal, motorized substitution weight(s) and the ability to use an external substitution weight(s). Item’s internal adjustment function shall have the option to be both automated (settings configured by user) or user-initiated.

3.2.1 Internal Substitution Weight: When using the internal substitution weight adjustment function, operator shall have the ability to edit the programmed mass value of the internal weight.

3.2.2 External Substitution Weight: When using an external substitution weight for adjustment, operator shall have the ability to enter/edit the actual mass value of the external weight(s).

3.3 Draft Shield: The Mass Comparator shall have a rigid, separate, external draft shield, which provides adequate space around the Mass Comparator.

3.3.1 Materials: External draft shield shall be composed primarily of at least 5 clear panes of Lexan, glass, or equivalent transparent material with 1/4 ± 1/16 inch thickness. Shield shall not be composed of Plexiglas due to inherent static properties.

3.3.2 Assembly: External draft shield shall come fully assembled or be assembled onsite by the OEM.

3.3.3 Functionality: The external draft shield shall be placed on a table and cover at least the entire weighing portion of the Mass Comparator. The shield shall allow for cords to be positioned as needed.

The operator shall be able to access the weighing pan to add and remove weights through the use of a sliding door or hinge mechanism.

3.3.4 Surface Area: Assembled closed draft shield shall not cover a surface area of more than 6 square feet.

3.4 Table: A marble table shall be provided that is large enough to hold both the comparator and draft shield. When on the table, the top of the comparator’s weighing surface shall be at or below 20 inches from the ground to accommodate the handling of large masses.

3.5 Calibration Adjustment: Any special equipment, software, fixtures, tools, standards, etc., required for calibration and alignment that are not common to a secondary calibration laboratory must be supplied with the Mass Comparator.

4.0 MECHANICAL & PHYSICAL REQUIREMENTS:

4.1 Components: Commercial parts and materials that are used shall have properties consistent with a precision laboratory instrument.

4.2 Weighing Pan: The Mass Comparator’s weighing pan/surface shall be made of stainless steel, or similar material, which resists rusting, chipping, flaking, or scraping.

4.3 Use of Best Commercial Practices: The equipment shall be designed and constructed of materials that meet the requirements of this specification and in accordance with the best commercial practices for industry approved equipment. It shall be designed and manufactured to maximize reliability, maintainability, accuracy of operation, and ease of operation. All parts (which include, but are not limited to, shafts, bearings, regulators, switches, controls) shall have proper clearance and adjustments. They shall work together so that the equipment will supply the rated requirements without unnecessary strains, vibrations, or overheating. They shall be able to withstand the conditions met in shipping, storage, installation, and service. All materials and parts of this equipment shall be capable of withstanding the environmental requirements of this specification.

4.4 Matched and Selected Components: These shall be kept to an absolute minimum. Use of specially built, nonstandard components shall be avoided.

4.5 Model and Serial Number Identification: Mass Comparator’s Part Number, Manufacturer, and Serial Number shall be identified clearly on the item in a location visible to the operator. Unique item identification shall follow Item Identification and Valuation requirements as stated in the contract.

4.6 Operating Environment/Storage:

4.6.1 Operating Temperature: The Mass Comparator shall be capable of operating in an ambient temperature of 67 to 79 degrees F without loss of required performance.

4.6.2 Operating Humidity: The Mass Comparator shall be capable of operating in an atmosphere from 20% to 50% relative humidity without loss of required performance.

4.7 Facility Electrical Power and Connections: The Mass Comparator shall be capable of operating on standard 110 V AC 60 Hz electrical power.

4.7.1 Electrical Safety: Documentation will be provided to support the means by which electrical safety considerations have been addressed. The safety of all personnel will be assured in conductive or nonconductive contact with the outside of the equipment, and during the changing of the fuse with the power to the system and its components are turned on. This documentation shall consist of a minimum of a citation of a UL or ANSI identified standard or equivalent United States Standard to which the equipment conforms.

5.0 OPERATOR’S MANUAL: Manual shall be IAW DD1423s and Data Item Descriptions, and shall include, at a minimum, the following information:

A. Setup/installation of Mass Comparator including external draft shield B. Procedure on how to adjust the Mass Comparator C. Drawing/Diagrams needed for adjustment D. A list of peripheral support equipment required to accomplish the adjustments E. Information on any internal adjustments made during operation F. Definitions on changeable settings G. Procedure on how to package, store and transport the Mass Comparator

6.0 INSTALLATION/TRAINING: OEM is responsible for the installation of the Mass Comparator onsite and provide 1 day of training.

7.0 ENVIRONMENT, SAFETY, AND OPERATIONAL HEALTH: A combination of the system manual, other documentation, and/or the system itself shall identify potential environment, safety and operational health hazards and how they are mitigated when the design itself cannot mitigate them. This will be accomplished through stating the hazard and accompanying mitigation through the use of safety devices, use of warnings, or use of special operational procedures to counter such hazards.

8.0 TESTING: This item will be inspected and accepted at destination as stated in the contract. The item will be checked with test equipment with parameters equal to or better than those required to assure that specified performance parameters are met. Test equipment used shall have first echelon certification directly traceable to the National Institute of Standards Technology (NIST) or other AFMETCAL-approved equivalent international laboratory. Tests will be performed to assure that the item meets the requirements of this purchase description. Such testing at destination does not relieve the contractor of performing all inspections and quality checks at the point of manufacture as necessary to assure performance as specified herein.

Attachment:

Data Requirements

Attachment to Purchase Description

24M-265A-MA

High Range Mass Comparator

DATA REQUIREMENTS

MANUALS: A complete user and service manual and calibration procedure shall be provided with each unit in contractor format. Manuals shall be on CD/DVD‐ROM in Indexed Portable Document Format

(iPDF). The manuals shall comply with Data Item Description (DID) DI‐TMSS‐80527C and the Contract

Data Requirements List (DD Form 1423).

FAILURE SUMMARY AND ANALYSIS REPORT: A complete Failure Summary and Analysis Report shall be provided once at the end of every Fiscal Year (once/if warranty repairs begin). The reports shall comply with Data Item Description (DID) DI-SESS-81495B and the Contract Data Requirements List (DD Form

1423).