ISEN – Low Pressure Diaphragm Gauge
ISEN Low Pressure Diaphragm Gauge is a mechanical pressure measuring instrument designed for applications where accurate measurement of relatively low pressure is required. Instead of using a conventional Bourdon tube, the gauge uses a single beryllium-copper diaphragm to detect pressure changes and convert them into pointer movement on an analog dial.
The gauge features a 2½-inch dial, black-finished drawn steel case, polycarbonate lens, aluminum dial, brass movement, and brass socket. Its specified accuracy is ±1.5% of full scale, exceeding ASME B40.100 Grade B requirements.
Designed for straightforward local pressure indication, the ISEN Low Pressure Diaphragm Gauge is suitable for equipment and process systems where operators need to read pressure directly at the measurement point without requiring an electronic transmitter or external power supply.
Diaphragm Principle for Low Pressure Measurement
The ISEN Low Pressure Diaphragm Gauge uses a flexible beryllium-copper diaphragm as its pressure-sensitive element. When pressure is applied through the process connection, the diaphragm deflects according to the pressure acting on it.
This small mechanical movement is transferred through the gauge’s internal movement mechanism and converted into pointer rotation. The pointer then moves across the graduated dial, allowing the operator to read the pressure directly.
The use of a diaphragm makes this type of gauge particularly appropriate for low-pressure measurement. Rather than relying on a relatively stiff Bourdon tube, the diaphragm can respond to smaller pressure changes.
The internal movement is manufactured from brass with precision-milled teeth, providing the mechanical connection between diaphragm movement and the pointer. The pointer itself is specified as a black, non-adjustable pointer, while the diaphragm is made from beryllium copper.
This mechanical operating principle also means the gauge does not require an electrical power supply simply to display the measured pressure. Pressure is converted directly into mechanical pointer movement, giving operators an immediate local indication.
2½-Inch Dial for Clear Local Pressure Indication
The ISEN Low Pressure Diaphragm Gauge uses a 2½-inch dial, providing a compact format for equipment panels, machinery, and local process installation.
The dial is made from aluminum with a white finish and black markings, creating a clear contrast between the scale and pointer. The gauge shown in the available configurations includes pressure scales such as psi and inH₂O, allowing the instrument to be selected according to the pressure measurement requirement.
A clear dial is particularly important for mechanical pressure gauges because the instrument is intended to be read directly by an operator. The large, easy-to-follow markings allow pressure conditions to be checked without connecting the instrument to a PLC, HMI, or other electronic monitoring system.
The polycarbonate lens uses a quarter-turn design, providing protection for the dial and pointer while maintaining visibility of the measurement scale.
The gauge is therefore suitable for applications where operators need a simple pressure indication directly at the equipment, especially when the measured pressure is low enough that a conventional high-pressure gauge would not provide the desired measurement sensitivity.
Construction and Material Selection
The ISEN Low Pressure Diaphragm Gauge combines several mechanical and protective materials selected for the different components of the instrument.
The gauge case is made from drawn steel with a black finish. The case provides the main external structure around the dial and internal movement.
The lens is manufactured from polycarbonate, providing a transparent protective cover over the dial. Polycarbonate is used here as a practical lens material for the compact pressure gauge design.
The dial uses finished aluminum with black markings, while the pointer is black and non-adjustable.
Inside the gauge, the movement is made from brass with precision-milled teeth. The diaphragm uses beryllium copper, while the socket is made from brass.
The process connection is also available in different configurations. The dimensional drawings show 1/4-inch NPT and 1/8-inch NPT connection options. The connection arrangement can be selected according to the available process port and installation requirements.
When specifying the gauge, Valvelink recommends checking the process connection, installation orientation, pressure range, process temperature, and compatibility of the wetted components with the measured medium.
Accuracy, Pressure Range and Operating Temperature
The ISEN Low Pressure Diaphragm Gauge is designed for applications where low-pressure measurement requires a clearly readable local indication.
The specified accuracy is ±1.5% of full scale. The available specification states that this performance exceeds the requirements of ASME B40.100 Grade B.
The gauge shown in the available documentation includes low-pressure scales such as 0–5 psi and 0–10 inH₂O, demonstrating its intended use for relatively low pressure or differential-pressure-related applications. The exact scale should be selected according to the required operating range.
Choosing an appropriate pressure range is important for mechanical gauges. The normal operating pressure should fall within the useful portion of the dial so that small pressure changes can be observed clearly without unnecessarily selecting a much larger range.
The specified process temperature range is -40 to 160°F (-40 to 70°C). The specified ambient temperature range is -40 to 140°F (-40 to 60°C).
These temperature limits should be considered during product selection and installation. If the process temperature can exceed the specified limit, an appropriate installation arrangement or alternative instrument may be required.
Process Connections and Installation Considerations
The ISEN Low Pressure Diaphragm Gauge is designed for direct mechanical connection to the pressure point being measured. The available dimensional drawings show 1/4-inch NPT and 1/8-inch NPT process connection options.
Before installation, the connection size and thread type should be checked against the process port. The gauge should be installed securely without applying excessive mechanical force to the case or movement.
The gauge should also be positioned where the dial can be easily seen by the operator. Since this is a local mechanical indicator, accessibility and viewing angle are important parts of the installation.
The pressure connection should be installed so that the diaphragm receives the process pressure correctly. The sensing system should not be subjected to pressure conditions beyond the selected gauge range.
The operating environment should also remain within the specified ambient temperature range of -40 to 60°C, while the measured process temperature should remain within -40 to 70°C.
For a reliable installation, the process connection, pressure range, temperature, mounting location, and measured medium should all be checked before commissioning.
Industrial Applications of Low Pressure Diaphragm Gauge
The ISEN Low Pressure Diaphragm Gauge is suitable for industrial equipment and process systems that require local indication of relatively low pressure.
Its compact 2½-inch format makes it appropriate for equipment where installation space is limited but a visible analog pressure indication is still required.
Potential applications include:
- Low-pressure process monitoring
- Air and gas pressure indication
- Equipment pressure monitoring
- HVAC and ventilation systems
- Filtration and flow-related equipment
- Low-pressure piping systems
- Industrial machinery
- Process skids and packaged equipment
- Local pressure indication on tanks and equipment
The diaphragm-based design is particularly useful where the pressure is relatively low and the application requires a mechanical gauge rather than a high-range pressure gauge.
The instrument can also be useful as a local reference alongside an electronic pressure transmitter. In such an arrangement, the transmitter can provide a signal to a PLC or SCADA system while the mechanical gauge allows an operator to visually check the pressure at the equipment.
When selecting an ISEN Low Pressure Diaphragm Gauge from Valvelink, key considerations include the required pressure range, scale unit, process connection, process temperature, ambient temperature, mounting arrangement, and compatibility of the pressure medium with the wetted materials.
With its single beryllium-copper diaphragm, brass precision movement, compact 2½-inch dial, polycarbonate lens, and ±1.5% full-scale accuracy, the ISEN Low Pressure Diaphragm Gauge provides a straightforward solution for local low-pressure measurement in industrial equipment and process systems.
