Pressure gauges have been used as the most common and reliable method for measuring pressure for more than a century now. With the development of the technology used in pressure gauges, the digital pressure gauge has gained great popularity for its convenient functionalities. Some of these are measuring liquids and air pressure in several applications such as hydraulics and pneumatics, pumps, medical, refrigeration controls, air compressors, utilities, and gas monitoring. Some of the digital pressure gauges have the additional configuration to show electrical output or monitor other variables like temperature. One of the important and most common applications that digital pressure gauges are used for is measuring the air compressor pressure. People related to the automotive industry often need it to measure the pressure of tires on a vehicle. This type of pressure gauges are often called digital air pressure gauges or tire pressure gauges and are highly demanded. Another high-range pressure gauge that is available for measuring the pressure of hydraulics is the digital hydraulic pressure gauge. It is installed at the pump’s pressure or anywhere on the machine to know the system pressure. Generally, the external build of a pressure gauge includes the Bourdon tube, socket, and geared movement, and also a pointer and dial to show process pressure.
Regardless of the application that you want to use a digital pressure gauge for, you need to consider a few things before choosing it.
Considerations to Make While Selecting The Right Digital Pressure Gauge
You need to consider several factors while choosing a digital pressure gauge for any application, some of which are:
Level of Accuracy
One of the first points to consider in a pressure gauge is the level of accuracy. The accuracy range varies from ±.25, ±.5, ±1, ±1.5, ±2 to ±2.5 percent. Most of the gauges come with different scale options for many single and dual-scale ranges. The level of accuracy can vary from newly designed systems to replacing components for the old ones. Usually, the more significant the application, the higher the accuracy required.
Engineering requirements suggest gauges with a larger dial size are the ones to look for as they can display the small and readable pressure readings, thus providing higher accuracy. Moreover, the user or operator’s convenience to read the scale with a larger dial is important as it allows to see the reading from a distance when the physical situations of the system or application demand.
You need to be very careful about the correct pressure range for a digital pressure gauge. You can go for full-scale pressure in case of dynamic pressure having the potential of pulses and surges. In such cases, the operating pressure is seen in the middle half (50%-75%) of the scale. It allows pressure swings as the pulsation and pressure spikes in the system.
Over Pressure Condition
Another important consideration you need to make while choosing a digital pressure gauge is the over-pressure condition. The pressure gauges are installed to monitor the pressure when process media flow through a pipe at comparatively high pressure. Any difficulties may occur in case the pumps are switched on/off, or the valves are opened/closed. The media then mounts through the pipe and a spike occurs on the gauge which can eventually damage the equipment. The pressure gauge should be compatible to meet these difficult conditions where pressure surges and spikes can occur. There are over-pressure protectors like the snubbers or the valves that can be applied to address these conditions.
Impact of Temperature
Temperature change has a large impact on the accuracy of a digital pressure gauge. Generally, a shift of 18°F (10°C) temperature from that the gauge is calibrated can show up to an additional error of ±0.4 percent. It happens because the Bourdon tube element’s elasticity or spring rate is affected by temperature. While avoiding the influence of air temperature is difficult, it is possible to address the process temperature. The common practice for that includes installing the pigtail siphons or the coil siphons to lessen the process heat. Another practice is seen where the diaphragm seal is installed with the capillary to isolate the gauge from the heat source. This allows the gauge to resist temperature up to 600°F. In a cold environment, it is better to elect heat trace instrumentation through steam or electric trace. The environment for applying a pressure gauge is important in terms of air temperature and process temperature. The above mounting options can be considered based on the working temperature range.
Corrosion is another cause for the failure of a pressure gauge. The material of the gauge is also important as the bourdon tube can be weak if the medium is corrosive. In such cases, problems like pinhole leakage or fatigue failure can occur due to stress cracking. You need to make sure that the media and case are chemically compatible. You should choose stainless steel over brass in terms of internal parts and casing. Diaphragm seals can also help to protect the gauge from the media.
Vibration can also affect the performance of the gauge. Internal working parts of a pressure gauge can be damaged if excessive wear is caused by the vibration of any rotating equipment like pumps or motors. It can be the bourdon tube or anything related to the movement or gear mechanism. It can also cause problems for accurate reading due to the oscillation of the pointer. Exposure to constant vibration often causes pressure gauge failure. A liquid-filled digital pressure gauge can very much solve the problem. The fluid should be either silicone or glycerin. It addresses the pointer oscillation and also lubricates the internal geared mechanism to ensure its safety.
The pressure gauges come in different designs in terms of process connections, sizes, and case mounting styles. The process connection must meet the system specifications and application need in order to work properly.
A standard digital gauge comes with a wide variety of accessories that you can take into consideration before choosing one.
- Piston and Sintered-Type Snubbers: It is useful for increasing gauge readability as it smoothens the pressure pulsation, surges, and spikes.
- Swivel Adapters: They are very handy for adjusting the line of sight to get a better reading position.
- Maximum Indicating Pointers: These are helpful to identify the system’s pressure spikes, especially during system startup and troubleshooting. Although care needs to be taken as they can add an additional error to the gauge due to the additional load on the Bourdon tube.
- Additional accessories: There are also many accessories available with the gauge like set-pointers that help to identify the minimum or maximum operating pressure or zero value, and rubber case protectors that help to protect gauges from situations when direct physical shock or vibration can happen.
Price may come as the last point but it certainly is not the least one to consider before choosing anything. The good thing is that the pressure gauge price has dropped drastically over the last few years. In the past, you might have expected to pay around $300 to $400 for a basic digital pressure gauge, whereas the mechanical gauges priced around $20. However, with the growth of technology and industry, you can purchase a digital pressure gauge for the price as low as $125 for high-end units or as low as $15 for a basic one.
The digital pressure gauge seems to be a very simple device, although it is important for you to make these considerations before getting a gauge in your hand. You may want to get the digital air pressure gauge for measuring the air pressure of your tires or want the digital hydraulic pressure gauge for measuring the pressure of high-end hydraulic units, doesn’t really matter why you want it for, what it matters the most is selecting the right type of gauge and accessories that perfectly fit your desired application.