Frequently Asked Questions

Pressure (symbol: p or P) is defined as the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled gage pressure) refers to the pressure measured relative to the ambient atmospheric pressure.

Pressure can be expressed in various units. Some units derive from a force unit divided by an area unit. For instance, the SI unit of pressure, the pascal (Pa), is equivalent to one newton per square meter (N/m²). In the imperial and US customary systems, pressure is traditionally measured in pounds-force per square inch (psi, symbol lbf/in²).

Pressure can also be expressed relative to standard atmospheric pressure. The atmosphere (atm) is a unit equal to standard atmospheric pressure, while the torr is defined as 1/760 of an atmosphere. Manometric units, such as the centimeter of water (cm H₂O), millimeter of mercury (mm Hg), and inch of mercury (in Hg), express pressure in terms of the height of a column of a specific fluid in a manometer.

A pressure gauge functions as a tool to measure pressure within compressed gases or liquids, finding applications across various industries. From checking tire pressure to monitoring blood pressure, pressure gauges play essential roles in everyday scenarios.

In industrial settings, these gauges serve to oversee pressurized systems, ranging from refrigeration units in food processing to machinery within nuclear power plants. Standard pressure gauges assess pressure relative to ambient atmospheric pressure, suitable for applications like boilers and compressed air systems.

Distinct types of gauges include vacuum gauges and absolute gauges, each providing readings against specific pressure references such as an absolute vacuum. Digital display pressure gauges offer ease of reading, while analog dial gauges provide direct linkage to the gauge for precise measurements.

In industries where precise measurements, such as pressure and temperature readings, are critical, a dependable calibration service is indispensable.

Calibration involves testing and adjusting measuring equipment to ensure accuracy, comparing their readings against highly accurate laboratory standards.

After calibration, you'll receive a certificate detailing the original readings and confirming alignment with national standards. We offer NQA ISO9001 calibration for pressure equipment, as well as traceable calibration for temperature, conductivity, torque, force, and more.

Regular calibration to national standards is essential for maintaining equipment accuracy and identifying any issues unrelated to calibration.

Pressure gauge calibration is determined by the end user. Generally, the more critical the industry the more often the gauge will need to be calibrated. It is usually written into the site procedure or manual. That said, annual calibration is the most common we come across. If you are unsure, please give us a call and our team will offer advice based on many years of experience. 

The methods of recording pressure, namely Gauge, Absolute and Differential, each serve distinct purposes.

Gauge pressure indicates the deviation from atmospheric pressure and can be either positive or negative. For instance, a typical dial pressure gauge registers gauge pressure, which is widely used globally.

Absolute pressure measures pressure relative to a complete vacuum and is always positive. A barometer, for example, measures absolute pressure.

Differential pressure compares pressure to another reference point and can be positive or negative. For instance, a manometer gauges the pressure difference across an air filter, indicating differential pressure.

There are many different units of pressure. Here is the conversions for the most used units: bar, PSI (pound-force per square inch) and Pa (Pascals).

1 bar = 14.5038 PSI = 100000 Pa

1 PSI = 0.0689476 bar = 6894.76 Pa

1 Pa  = 0.000145038 PSI = 1e-5 bar

We often see gauges using other units of pressure so don't hesitate to contact us if you don't see the units used on your gauge!

Diaphragm gauges are frequently utilized in situations where clogging poses a concern. These gauges are designed without a small inlet hole, which prevents the medium from compacting and creating blockages. Diaphragm gauges are available in a range of types to suit different applications, including flanged models for secure installation and hygienic versions with a nut and liner for easy cleaning and maintenance in sanitary environments. Their robust design ensures reliable performance in challenging conditions where other gauges might fail due to clogging.

The liquid fill inside the gauge's head functions as an effective damping mechanism for its moving parts. This liquid cushioning significantly reduces the impact of vibrations, pulsations and general wear and tear, thereby enhancing the durability and reliability of the gauge in demanding environments. By minimising these potentially damaging factors, the liquid fill ensures consistent and accurate performance over a longer lifespan. We most typically come across gauges filled with water, oil or glycerin. However, there are many different fillings used as per the requirements of the gauge.

F.S.D. (Full Scale Deflection) or F.S. (Full Scale) pertains to the gauge's accuracy. This terminology signifies that the accuracy, denoted as C.L. (Calibration Limit) or K.L. (K-factor Limit), is measured across the entire range of the gauge. Essentially, F.S.D. or F.S. represents the highest value within the gauge's measuring capacity for which it has been calibrated. This ensures that the specified accuracy is maintained consistently throughout the full spectrum of measurement, from the lowest to the highest readings the gauge can record.

         Accuracy Class                                    Limits of permissible error (% of span)

        0.1                                                              ± 0.1 %

        0.25                                                           ± 0.25 %

        0.6                                                             ± 0.6 %

        1                                                                 ± 1 %

        1.6                                                              ± 1.6 %

        2.5                                                             ± 2.5 %

        4                                                                ± 4 %

Temperature mapping involves strategically placing data loggers throughout a designated area for a minimum duration of 24 hours. These data loggers continuously record temperature and humidity levels, providing a comprehensive study of their distribution within the environment. By analysing this data, companies can identify inconsistencies such as hot spots and areas of fluctuation.

The primary objectives of temperature mapping are to detect hot spots, understand how internal temperatures are influenced by external climatic changes, and improve the management of product storage conditions. This detailed information helps in optimising environmental controls, ensuring that products are stored under ideal conditions to maintain quality and safety.

To achieve accurate and representative results, it is recommended that temperature mapping be conducted twice a year: once in the summer and once in the winter. This seasonal assessment accounts for the varying external temperatures and their impact on the internal environment, allowing for more effective adjustments and consistent climate control throughout the year.

Portable appliance testing (PAT) refers to the process of inspecting and testing electrical appliances and equipment to ensure their safety. While many electrical safety defects can be identified through visual examination, certain defects require testing to be detected. It is important to note that visual examination remains a crucial part of the safety assessment, as some defects are not identifiable through testing alone.

A brief user check, performed with basic training and possibly a simple checklist, can significantly enhance an electrical maintenance regime. However, depending on the type of equipment and its operating environment, more formal visual inspections and testing by a competent person may be necessary at regular intervals. This comprehensive approach ensures that all potential safety issues are addressed, maintaining the overall safety and functionality of the electrical equipment.

Metrology, the scientific study of measurement, plays a crucial role in establishing standardised units and ensuring consistency across various applications. It encompasses three core activities:

- Defining units of measurement.

- Implementing these units practically.

- Maintaining traceability by linking practical measurements to established reference standards.

In every country, a national measurement system (NMS) operates as a network of laboratories, calibration facilities, and accreditation bodies. These entities collectively uphold and advance the country's metrology infrastructure, ensuring accurate and reliable measurements essential for scientific, industrial, and regulatory purposes.