ISO 17025 accredited

# Vacuum Gage Calibration

Capabilities:

• Pressure Gage- 0 to 14,500 psig
• Pressure Devices- 2 to 10,000 psig
• Vacuum Gage- -14.5 to 0 psiv

### Basics of Vacuum

Evacuating air from a closed volume develops a pressure differential between the volume and the surrounding atmosphere. If this closed volume is bound by the surface of a vacuum cup and a workpiece, atmospheric pressure will press the two objects together. The amount of holding force depends on the surface area shared by the two objects and the vacuum level. In an industrial vacuum system, a vacuum pump or generator removes air from a system to create a pressure differential.

Because it is virtually impossible to remove all the air molecules from a container, a perfect vacuum cannot be achieved. Of course, as more air is removed, the pressure differential increases, and the potential vacuum force becomes greater.

## Vacuum Pressure

By definition, vacuum is a space that is partially exhausted (as to the highest degree possible) by artificial means (such as an air pump). This definition is referring to a high or hard vacuum. Figure 1 illustrates that relationship of absolute and gauge pressure with 0 PSIA equal to a high or hard vacuum.

## Gauge Pressure

Gauge pressure is pressure measured relative to ambient atmospheric pressure (approximately 14.7 PSIA). It is referred to as pounds per square inch (gauge) or PSIG. The electrical output of a gauge pressure transducer is 0 VDC at 0 PSIG (14.7 PSIA) and full scale output (typically 5 VDC) at full-scale pressure (in PSIG).

## Absolute Pressure

Absolute pressure is measured relative to high vacuum (0 PSIA). It is referred to as pounds per square inch (absolute) or PSIA. The electrical output of an absolute pressure transducer is 0 VDC at 0 PSIA and full-scale output (typically 5 VDC) at full-scale pressure (in PSIA).

Vacuum can refer to any pressure between 0 PSIA and 14.7 PSIA and consequently, must be further defined. For applications concerned with measuring vacuum pressures over this full range, two different approaches are often taken.

Vacuum pressure is measured relative to ambient atmospheric pressure. It is referred to as pounds per square inch (vacuum) or PSIV. The electrical output of a vacuum pressure transducer is 0 VDC at 0 PSIV (14.7 PSIA) and full-scale output (typically 5 VDC) at full-scale vacuum, 14.7 (0 PSIA).

The vacuum pressure transducer gives an increased positive voltage output proportional to decreasing pressure (increasing vacuum). The absolute pressure transducer gives an increased positive voltage output proportional to increasing pressure (decreasing vacuum).

### What Is Pressure?

Pressure is defined as force per unit area that a fluid exerts on its surroundings. Pressure, P, is a function of force, F, and area, A:

P = F/A

The SI unit for pressure is the pascal (N/m2), but other common units of pressure include pounds per square inch (psi), atmospheres (atm), bars, inches of mercury (in. Hg), millimeters of mercury (mm Hg), and torr.

A pressure measurement can be described as either static or dynamic. The pressure in cases with no motion is static pressure. Examples of static pressure include the pressure of the air inside a balloon or water inside a basin. Often, the motion of a fluid changes the force applied to its surroundings. For example, say the pressure of water in a hose with the nozzle closed is 40 pounds per square inch (force per unit area). If you open the nozzle, the pressure drops to a lower value as you pour out water. A thorough pressure measurement must note the circumstances under which it is made. Many factors including flow, compressibility of the fluid, and external forces can affect pressure.

### for more capabilities.

Gage ID Number

Description and Size of Gage

Calibration Cycle

Check Points (if not specified, we adhere to our quality policy)

Gage ID is the unique identifier you use to identify the specific piece of equipment.

Calibration Cycle is the interval between calibrations.

We use this information to provide a sticker for the calibrated instrument to show when it was calibrated and when you want it calibrated again.

YES!

Please include power cords, leads, and any accessories necessary for us to perform the calibration.

All ISO 17025 accredited calibrations are traceable through NIST or another NMI(National Metrology Institute) to the SI Unit.

Calibration certificates include as-found data, as-left data, and measurement uncertainty.

Alliance Calibration

Cincinnati, OH 45241

We do offer onsite calibration service within a 150-mile radius. Not all calibrations are best suited for onsite calibration.