Purchase_Description_19M-233A-MA_Rev._0_dated_11_October_2018.pdf

19M-233A-MA

11 October 2018

Revision 0

Attachment 1

PURCHASE DESCRIPTION

FOR

220g Mass Comparator

1.0 SCOPE: This purchase description specifies a Mass Comparator to be used in the calibration of mass standards by selected Precision Measurement Equipment Laboratories (PMELs) to calibrate both Avoirdupois and Metric working standard masses in the range of 22 to 220 grams. Metric primary standards shall be used to calibrate Avoirdupois working standard masses using this device.

2.0 PERFORMANCE REQUIREMENTS:

2.1 Display Resolution: The Mass Comparator shall be readable to 0.01 milligram.

2.2 Measuring Range: The Mass Comparator shall have a continuous metric range, which covers 22 to 220 grams minimum.

2.3 Repeatability: The repeatability of the Mass Comparator shall not exceed 0.02 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 differences between two master weights of the same nominal value.

2.4 Reliability: The Mass Comparator shall maintain its repeatability specification over a period of 12 months, minimum.

2.5 Shift Test/Eccentricity: The Shift Test error of the Mass Comparator shall not exceed 0.15 milligrams throughout the Measuring Range (see PD paragraph 2.2 above).

2.6 Stabilization Time: The stabilization time for an individual reading shall be no more than 10 seconds.

3.0 FUNCTIONAL REQUIREMENTS:

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

3.1.1 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.

3.1.1.1 Internal Substitution Weight: When using the internal substitution weight(s) for adjustment, operator shall have the ability to edit the programmed value(s) for the internal weight(s).

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

3.2 Ancillary Equipment: The Mass Comparator shall have a rigid, separate, external draft shield, which provides adequate space around the Mass Comparator and easy access to the weighing chamber.

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3.2.1 Materials: External draft shield shall be composed primarily of at least 5 clear panes of Lexan, glass, or equivalent transparent material with ¼ +/- 1/16 inch thickness. Shield shall not be composed of Plexiglas due to inherent static properties.

3.2.2 Assembly: External draft shield shall come fully assembled, or be assembled in-situ by the manufacturer’s trained technician.

3.2.3 Functionality: External draft shield shall be placed on a table and shield entire weighing portion of the Mass Comparator, and allow for cords, such as power cords, to be positioned as needed.

External shield shall function such that the operator is able to access the Mass Comparator’s weighing pan through the internal draft shield in order to add and remove weights as necessary to perform measurements through the use of a sliding door or hinge mechanism.

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

3.3 Calibration Adjustment: Any special equipment, fixtures, tools, standards, etc., required for calibration and are not common to a secondary calibration laboratory must be supplied with the Mass Comparator. A unit that fails calibration and is recommended to be aligned or adjusted in order to meet all requirements of para 2.0, either manually or using alignment/adjustment software, shall include any special hardware, software, software licenses needed to perform the alignment/adjustment process.

4.0 MECHANICAL & PHYSICAL REQUIREMENTS:

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

4.1.1 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. Weighing pan/surface shall not be composed of, or covered in, a soft material, such as cork, which may flake, disintegrate, or rub off over time.

4.2 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.

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

4.4 Model and Serial Number Identification: The 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 the Item Identification and Valuation clause as stated in the contract.

4.5 Operating Environment/Storage:

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4.5.1 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.

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

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

4.7 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 that the equipment conforms to.

4.8 Working Height: The Mass Comparator’s weighing pan surface shall be located no more than 8 inches higher than the Mass Comparator’s supporting table. In addition, when moving a weight from the Mass Comparator’s supporting table and onto the weighing pan, the weight shall be lifted no more than 8 inches vertically, with no obstructions from the External Draft Shield (see PD paragraph 3.2 above).

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 balance including external draft shield B. Procedure on how to adjust the balance, if necessary, per paragraph 3.3 above 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 balance

6.0 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 19M-233A-MA

220g 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).