Analog Gauges vs. Digital Gauges

An analog gauge or a digital gauge is an instrument that can measure and display the value of a physical characteristic.

Instrumentation plays a critical role in all types of industrial processes, as timely and accurate readings of various parameters, such as temperature, flow, and pressure are necessary to ensure safe and efficient operations. In industrial processes, temperature and pressure are the two most commonly measured characteristics. Usually, gauges display values in real-time, making these instruments crucial in a plant’s day-to-day operations; pressure gauges, temperature gauges, and flowmeters are a few of the most common types of gauges.

Before selecting a specific gauge for your application, it’s important to have a full understanding of the differences between digital and analog models.

Features and Benefits of Analog and Digital Gauges

Most physical parameters relevant to process industries can be measured using analog or digital gauges, also referred to as meters.

Analog meters usually have a needle that directly responds to changes in a given parameter. A scale is calibrated such that the moving needle accurately represents the variation in the physical quantity. For example, an analog pressure gauge is directly exposed to the fluid whose pressure is to be measured. The changes in pressure move the needle proportionally, thus allowing for pressure measurements. Similarly, variations in temperature, flow, and other characteristics can be translated to a proportional mechanical movement of a gauge needle. Analog gauges are the traditional instrument choice.

However, digital gauges are becoming more and more popular. These electronic devices employ a transducer that converts the variations in the characteristic to be measured into a proportional electrical signal. This signal is then converted to a numeric value using a microprocessor, which is then displayed on a digital display.

Both types of gauges offer unique advantages. For example, since analog meters are mechanical devices, they require no power supply. And because they measure quantities on a single continuous dial, the rate of change of the characteristic being monitored can be easily inferred. Additionally, any variations can be noticed easily, as they translate into movement of the gauge’s needle. Analog models represent a mature technology, allowing for easier operation and repair by technicians and field engineers who are familiar with the underlying principles of operation.

Digital gauges have the advantage of being more precise and can be designed to display readings in multiple units and formats as the application dictates. Often, a single digital gauge can replace an array of analog gauges. Digital meters also offer sophisticated features, such as a display showing the safe limits of the characteristic being measured.

The Drawbacks of Digital and Analog Gauges

Digital and analog industrial gauges are not without their drawbacks, however. For example, a digital gauge, while precise, may not be easy to interpret in a setting where dynamic changes in multiple quantities need to be observed simultaneously.

Also, in situations involving rapid changes or spikes in a monitored parameter, analog gauges display the average value, while digital gauges necessitate manual calculation of the value. Digital gauges are also more expensive than analog gauges. On the other hand, analog gauges often result in parallax error, caused by taking a reading from a position where the line of vision is not perpendicular to the plane of the gauge face, making them unsuitable for applications requiring optimal precision.

Analog meters cannot be employed in applications in which vibration is common, as the mechanical systems may fail under such circumstances. And finally, it’s difficult to employ analog meters in low-light conditions, as their displays are usually not lit.

Choosing the Right Type of Gauge

Choosing between a digital gauge and an analog gauge can be a complex decision; users must carefully assess the unique requirements of their specific application and weigh all pros and cons before selecting instrumentation.

For example, in cases requiring precision, vibration tolerance, or low-light operation, a digital gauge proves to be the better option. But if multiple readings and rate of change are to be measured with a lower degree of precision, then analog meters can provide a reliable, low-cost solution.

To ensure you’re working with the ideal gauge for your unique application, partner with a trusted supplier who can guide through every step of the selection process.

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