FAQ - Instruments
Accurate measurement is the basis of safe and efficient process control. Below we answer frequently asked questions about the pressure gauges, pressure sensors, flow controllers, flow switches and flow meters supplied by Ingenieursburo Gommer.
Our instrumentation range covers mechanical pressure gauges, electronic pressure sensors and transmitters, Coriolis and ultrasonic flow controllers, Coriolis, ultrasonic and paddlewheel flow meters, flow switches with fixed or adjustable set points, explosion-proof flow switches and excess flow valves. View Instruments on the Gommer website.
Consider normal operating pressure, maximum pressure, required accuracy, dial size, connection position, process medium, vibration and pulsation. A gauge should generally operate well within its full-scale range rather than continuously near its maximum. View Pressure Gauges on the Gommer website.
Operating around the central portion of the scale generally improves readability and gives margin for pressure fluctuations. It also prevents the gauge from continuously operating near its maximum range.
A Bourdon gauge uses an elastic curved metal tube that moves as internal pressure changes. The movement is mechanically transferred to the pointer.
A diaphragm gauge senses pressure using a flexible diaphragm. It can be particularly suitable for relatively low pressures or applications requiring separation between the process and gauge mechanism.
A capsule element consists of thin diaphragms joined together to form a pressure-sensitive chamber. Capsule gauges are well suited to very low gas and differential pressures.
Glycerine or silicone filling can damp pointer movement caused by pulsation and vibration. The filling also reduces internal condensation and mechanical wear.
A diaphragm seal separates a pressure instrument from the process medium while transmitting pressure hydraulically to the instrument. It is useful for corrosive, viscous, crystallising, sanitary or high-temperature media.
A snubber restricts rapid pressure pulsations before they reach a pressure gauge or sensor, improving readability and protecting the instrument from repeated dynamic loading.
A siphon is commonly installed between hot steam and a pressure instrument. Condensate retained in the siphon provides a thermal barrier that protects the instrument from direct exposure to steam temperature.
The terms overlap, but a transmitter normally refers to a sensor with conditioned industrial output such as 4–20 mA. A transducer may provide voltage or another direct electrical output.
A current loop is relatively resistant to voltage drop and electrical noise over long cable distances. The 4 mA live zero also helps distinguish a zero measurement from loss of power or a broken circuit.
Depending on product family, options can include 0–10 V, 0–5 V, HART, IO-Link, Modbus, CAN-based communications and other digital interfaces.
HART adds digital communication to a conventional analogue 4–20 mA loop, allowing additional device information, configuration and diagnostics while retaining the analogue process signal.
IO-Link is a point-to-point digital communication standard used with intelligent sensors and actuators. It can provide measurement data, diagnostics and parameterisation through compatible automation infrastructure.
Accuracy specifications can include non-linearity, hysteresis, repeatability and temperature effects. Two transmitters advertised with the same headline percentage are therefore not necessarily identical.
Turndown describes how far a transmitter or measurement device can be ranged below its nominal span while maintaining specified performance.
A Coriolis meter measures mass flow by detecting changes in vibrating measuring tubes caused by flowing fluid. Many designs can simultaneously provide density and temperature information. View Coriolis Flow Meters on the Gommer website.
Advantages can include direct mass-flow measurement, high accuracy, measurement of liquids and many gases and no conventional rotating measuring element. Malema offers Coriolis technology for demanding industrial and high-purity applications.
It measures mass flow directly, reducing dependence on fluid density compared with volumetric technologies. However, installation, two-phase flow and process conditions can still affect performance.
An ultrasonic meter uses acoustic signals to determine flow velocity. Depending on design, it may use transit-time or other ultrasonic measurement principles. View Ultrasonic Flow Meters on the Gommer website.
Potential advantages include no mechanical rotating parts, low pressure drop, fast measurement and compatibility with specialised wetted materials and high-purity designs.
A paddlewheel meter uses a rotor positioned in the flowing liquid. Rotor speed is related to fluid velocity and therefore to volumetric flow. View Paddlewheel Flow Meters on the Gommer website.
The choice depends on gas or liquid, flow range, pressure, temperature, required accuracy, chemical compatibility, cleanliness, pressure-drop limitations and available installation length.
A flow controller combines a measuring element with a control valve and control electronics to maintain a requested flow set point. View Flow Controllers on the Gommer website.
It combines direct mass-flow measurement with active control, providing accurate dosing or gas/liquid delivery where changes in process pressure would otherwise change flow.
An ultrasonic flow controller uses ultrasonic measurement together with an integrated control valve or actuator. It can be attractive for applications requiring low pressure drop or specialised wetted materials.
A meter measures flow. A controller measures flow and actively changes a valve or other control element to maintain a target flow.
A flow switch provides a discrete electrical signal when flow crosses a defined threshold. It is used for alarms, permissives and equipment protection. View Flow Switches on the Gommer website.
A fixed set-point device is calibrated to operate at a predetermined flow. An adjustable switch allows the operating point to be set in the field or during commissioning.
Use a flow switch when the main requirement is simply to confirm adequate flow or generate an alarm. Use a meter when the actual flow value must be measured, displayed or transmitted.
These products are designed and certified for installation in defined hazardous environments. The required certification depends on zone, gas or dust group, temperature class and installation method.
An excess-flow device reacts when flow rises above a designed threshold, for example after a downstream hose or line failure. It can limit uncontrolled discharge. View Excess Flow Valve on the Gommer website.
Yes, depending on system arrangement. A downstream flow switch can signal when flow has fallen below an acceptable limit. View Filters on the Gommer website.
Depending on instrument type, options can include 316L stainless steel, Hastelloy, Monel, Inconel, specialised metals, PFA, PTFE and PVDF.
For corrosive applications, every wetted surface must be considered. Metal-alloy diaphragms, polymer flow bodies or diaphragm seals can allow measurement of media unsuitable for conventional stainless-steel instruments.
Semiconductor applications can require extremely low particle generation, high-purity wetted materials, low dead volume and controlled cleaning and packaging. Malema products are used in demanding high-purity fluid systems.
Selected instruments can be supplied in configurations suitable for oxygen service. Cleanliness, wetted materials and pressure must all be evaluated.
Yes. Pressure sensors, gauges, flow instruments and switches can be selected for hydrogen, subject to pressure, material and leakage requirements.
Many pressure and flow instruments are available with ATEX and/or IECEx certification. Correct selection requires the full hazardous-area classification.
Measurement instruments should be calibrated at intervals appropriate to the required accuracy, process criticality and quality system.
Calibration determines the relationship between the instrument reading and a reference. Adjustment changes the instrument to reduce measurement error.
Traceability means the measurement result can be linked through a documented chain of calibrations to recognised measurement standards, each with stated uncertainty.
Many instruments can be supplied with manufacturer calibration documentation or additional traceable calibration, depending on product and required certificate level.
Yes. Assemblies can include a gauge or transmitter, isolation valve, bleed valve, manifold, snubber, siphon, diaphragm seal and tube fittings. View Valves and Fittings on the Gommer website.
Yes. Flow switches, flow meters, pressure gauges and transmitters can be integrated with regulators, filters, sample coolers and valves. View Sampling and Systems on the Gommer website.
Useful information includes medium, normal and maximum pressure, temperature, flow range, required accuracy, connection type, wetted-material requirements, desired output, power supply, hazardous-area classification and calibration requirements.
Ingenieursburo Gommer can help compare pressure and flow technologies against the actual process conditions and required measurement performance. Send us your process data and application requirements.