L. J. Engineering manufacturers digital vacuum gauges and digital pressure gauges designed to function as stand-alone instruments for reading vacuum and pressure of dry gases. OEM versisions of the gages are also available for easy integration into OEM product designs. Optional liquid/air separator filters are available for systems containing liquids. Various pressure and vacuum ranges, as well as different units of measure, are available. Pressure ranges and display resolution are shown in the table below. All units have an accuracy of +0.25% of the full scale display reading. A calibration certificate showing actual test values can be furnished for a nominal charge.

Pressure and Vacuum Measuring Scale Vacuum can be measured either as differential vacuum or absolute pressure. Differential Vacuum Gauges or simply vacuum gauge is the measurement of the pressure difference relative to the surrounding atmospheric pressure. Therefore, a zero reading occurs when no vacuum is present. A perfect vacuum (zero absolute pressure) when measured as a differential vacuum will indicate the ambient atmospheric pressure. If a constant differential vacuum is maintained, the absolute pressure will fluctuate over time at a given location due to weather (barometric pressure) changes. Differential vacuum measurement and control is useful in applications where it is desirable to maintain precise control of vacuum relative to atmospheric pressure, such as in the case of low pressure vacuum clamping of delicate or fragile parts and any other applications where it is important to maintain a constant vacuum regardless of changes in atmospheric pressure. Higher vacuum applications utilize pressure settings that are closer to a perfect vacuum and are usually measured in units of absolute pressure. Absolute Pressure Gauges measurement relative to a perfect or zero vacuum, as in outer space. A zero reading occurs when the pressure is reduced to near perfect vacuum conditions. Therefore, when no vacuum is applied, the measured pressure is the ambient atmospheric pressure, which at sea level is approximately 29.92 inches of mercury, or 14.7 pounds per square inch, or 760 mm of mercury. Differential Pressure Gauges measure between to different pressure sources. For example it could be the pressure difference across a filter, valve or restrictor. Differential pressure gauges require that the proper pressure relationship is applied to the corresponding port. In other words the high pressure port must always be at a pressure equal to or greater than the pressure applied to the low pressure port. The Digital Vacuum Gauge and Digital Pressure Gauge are enclosed in a high-impact, splash-resistant ABS plastic case with mounting flanges to permit attachment to a flat surface. A 120 VAC wall transformer is included. The Digital Vacuum Gauge and Digital Pressure Gauge features 0.56-inch red LED numbers to provide optimum readibility. A variety of OEM (original equipment manufacturer) models are available to permit easy integration of the gauge display assembly into a user's control panel. The OEM models require the user to provide a DC power source of 8 to 15 volts at 250ma (minimum supply current). Please contact the factory for other pressure/vacuum ranges and units of measure or special options such as an analog