CSS 06-3230 V1.pdf

CALIBRATION STANDARD SPECIFICATION

ABSOLUTE GAS PISTON GAUGE

SALIENT CHARACTERISTICS

DEPARTMENT OF THE NAVY

METROLOGY AND CALIBRATION PROGRAM

CSS 06-3230

DISTRIBUTION STATEMENT A APPROVED FOR PUBLIC RELEASE, DISTRIBUTION IS UNLIMITED.

FEBRUARY 2024

CALIBRATION STANDARD SPECIFICATION

ABSOLUTE GAS PISTON GAUGE

SALIENT CHARACTERISTICS

Prepared by:

Brett Culbertson

Physical/Mechanical Measurements Branch (MS 33)

Measurement Science Department

Naval Surface Warfare Center, Corona Division

P.O. Box 5000

Corona, CA 92878-5000

DEPARTMENT OF THE NAVY

METROLOGY AND CALIBRATION PROGRAM

Table of Contents

SCOPE

1.1 General

1.2 Usage

GENERAL REQUIREMENTS

2.1 Measurement Theory and Configuration

2.1.1 Piston/Cylinder Assembly

2.1.2 Mass Set

2.1.3 Base Unit

2.2 Size and Weight

2.3 Electrical power source

2.4 Environmental requirements

2.4.1 Warm-up

2.4.2 Temperature and Relative Humidity

2.4.3 Vibration

2.4.4 Local Gravity

PERFORMANCE REQUIREMENTS

3.1 Range and Measurement Uncertainty

3.1.1 Range

3.1.2 Measurement Uncertainty

3.2 Environmental Monitoring

3.3 Base Unit Monitoring

3.4 Pressure and Vacuum Control

3.5 Automation

3.5.1 Pressure Calculation

3.5.2 Operation

3.5.3 Mass Loading

ACCESSORIES

4.1 Display and Control Unit

4.2 Pressure Supply

4.3 Vacuum Supply

4.4 Interconnections

4.5 External Connections

4.6 Calibration Documentation

SCOPE

1.1 General.

This document specifies the salient requirements for an Absolute Gas Piston Gauge (AGPG). The AGPG will be used to calibrate pressure measuring equipment in a controlled laboratory environment. The AGPG shall generate absolute and gauge pressures, with automated or semi-automated operation.

This equipment may be of a commercial design or a modified commercial design.

1.2 Usage.

The requirements of this specification are tailored to the intended use of the equipment. The AGPG is intended to be used by civilian and uniformed Navy personnel to calibrate pressure measuring equipment in a controlled laboratory environment. This includes, but is not limited to, pressure gauges, transducers, calibration standards, and air data test and measuring equipment.

GENERAL REQUIREMENTS

2.1 Measurement Theory and Configuration.

The AGPG shall be a pneumatic piston gauge, which generates pressure using the general principle of pressure equals force per unit area, P = F/A. The three

(3) major components are listed below.

In practice, pressure is generated by loading known masses onto a piston/cylinder assembly. Pneumatic pressure is applied to the other side of the piston/cylinder assembly until the system is balanced, or floating. Several additional environmental and system parameters are measured, controlled, and corrected for, resulting in a highly accurate calculated pressure.

The AGPG shall also be capable of absolute pressure generation by applying a vacuum to the mass and piston/cylinder setup. The method is otherwise the similar, with calculations altered to reflect the measured vacuum instead of ambient conditions.

2.1.1 Piston/Cylinder Assembly

The AGPG shall include one (1) or more piston/cylinder assemblies, with nominal area as appropriate for generating pressure over the full operational range.

Material, thermal coefficient, and other relevant physical characteristics shall be specified in AGPG documentation.

2.1.2 Mass Set.

The AGPG shall include a set of known masses, including a mass holder, capable of generating pressure over the full operational range. Material, mass values, and other relevant physical characteristics shall be specified in AGPG documentation.

2.1.3 Base Unit.

The AGPG shall include a base unit, on which the piston/cylinder assembly is installed and external pressure and vacuum are applied to balance the system.

2.2 Size and Weight.

The AGPG shall be sized for operation on a typical workbench, with a working surface of 6 ft (width) x 2.5 ft (depth). Vacuum pumps and pressure supply can be located either under or beside the workbench, but other components shall fit on the working surface.

2.3 Electrical power source.

The AGPG shall operate using single phase 115 VAC 50/60 Hz electrical power.

Multiple outlet connections for separate components are acceptable.

2.4 Environmental requirements.

The AGPG environmental performance requirements shall be as specified below.

It shall conform to the specified performance requirements of section 3.0 when subjected to the following environmental conditions.

2.4.1 Warm-up.

The AGPG shall conform to the specified performance requirements with no longer than a 60-minute warm-up period. This period shall include any required temperature stabilization in the use environment.

2.4.2 Temperature and Relative Humidity.

The AGPG shall conform to the specified performance requirements while operating in the temperature and relative humidity ranges specified below.

Storage in the ranges specified below shall not affect the ability of the AGPG to conform to the specified performance requirements.

Temperature

(F)

Relative Humidity

(% RH)

Operating 64 to 82 20 to 60

Storage -40 to 158 0 to 90

2.4.3 Vibration.

The AGPG shall conform to the specified performance requirements while operating in an environment subject to the following ambient vibrations.

Frequency (Hz)

Velocity (in./sec)

Acceleration (g pk)

8 to 100 up to 0.002 up to 0.003

2.4.4 Local Gravity.

The AGPG shall conform to the specified performance requirements assuming local gravity is known with a measurement uncertainty (k=2) of up to ±1x10-6 m/s2 (±0.1 mGal).

PERFORMANCE REQUIREMENTS

3.1 Range and Measurement Uncertainty.

The AGPG shall generate pressure over the following range and measurement uncertainty.

3.1.1 Range.

Defined as the minimum and maximum pressure generated by the AGPG in both gauge and absolute modes.

0.25 to 50 psi

3.1.2 Measurement Uncertainty.

Defined as the maximum deviation from the true value of pressure, including the combined effects of linearity, repeatability, hysteresis, and stability, throughout the operating temperature range. Based on a one year calibration interval and a k=2 coverage factor (approximately 95% coverage probability).

±10 ppm or 1.5x10-5 psi, whichever is greater

3.2 Environmental Monitoring.

The AGPG shall include all equipment necessary to measure all environmental parameters that contribute to the calculation and measurement uncertainty of the pressure generated. These include, but may not be limited to barometric pressure, ambient temperature, relative humidity, air density.

3.3 Base Unit Monitoring.

The AGPG shall include all equipment necessary to measure all base unit parameters that contribute to the calculation and measurement uncertainty of the pressure generated. These include, but may not be limited to, piston/cylinder temperature, piston/cylinder float position, sink rate, and reference vacuum.

3.4 Pressure and Vacuum Control.

The AGPG shall include all equipment necessary to control pressure and vacuum required for operation.

3.5 Automation.

The AGPG shall be capable of automated or semi-automated operation as defined below.

3.5.1 Pressure Calculation.

The AGPG shall calculate the mass load required to generate pressure requested by the operator. The AGPG shall calculate the real-time pressure generated by that mass load with limited or no manual inputs from the operator.

Manual calculations shall not be required of the AGPG operator.

3.5.2 Operation.

The AGPG shall control/adjust pressure and vacuum supplies to the base unit, and also float and rotate the piston. The AGPG shall indicate when the system is stable and generating the requested pressure.

Note: The AGPG shall also be capable of manual control, float, and rotation if the automated method limits the operational range or measurement uncertainty.

Manual operation shall not be interpreted to allow manual calculations.

3.5.3 Mass Loading.

Automated mass loading of the AGPG is acceptable, but not required.

ACCESSORIES

4.1 Display and Control Unit.

The AGPG shall include a display capable of indicating the generated pressure with sufficient resolution to maintain the specified measurement uncertainty. The display shall be part of or connected to a control unit. The control unit and display component(s) shall be responsible for storage of calibration data (constants, mass values, etc.), aggregation of environmental and base unit measurements, and performing calculations. The control unit and display component(s) shall accept any necessary inputs from the operator. The control unit and display component(s) may take the form of a personal computer (PC), but this is not required.

4.2 Pressure Supply.

Not required. The Navy will provide high purity Nitrogen for pressure supply, but any purity or other requirements shall be specified in AGPG documentation.

4.3 Vacuum Supply.

The AGPG shall include any vacuum pump(s) required for operation.

4.4 Interconnections.

The AGPG shall include all hoses, fittings, adapters, cables, and other parts required to connect and operate all components of the system.

Note: The Navy will provide the high purity Nitrogen supply, including a regulator assembly.

4.5 External Connections.

No specific connector is required for the AGPG outlet port that connects to the test instrument (TI) (also referred to as the unit under test (UUT)).

4.6 Calibration Documentation.

All AGPG equipment that contributes to the overall measurement uncertainty of the system shall be delivered with proof of calibration traceable to the International System of Units (SI). Documentation providing traceability through a national metrology institute, NIST for example, is acceptable. All measurements should be reported with an expanded measurement uncertainty at a k=2 coverage factor.