# Differential Pressure Gauge

The measurement of the difference between two pressures is the foundation of differential pressure gauge theory. Differential pressure, as its name implies, measures two pressures and shows the difference between them.

Simply put, a DP gauge measures the pressure difference between two connections. As a result, let’s imagine an application where you have one tank at 100 psi and the other at 95 psi. If you install a differential pressure gauge between those two vessels, you will read 5 psi.

There are a few different gauge designs to achieve this, but differential pressure plus what is known to manufacturers as “magnetic coupling”. Each gauge has a magnetic piston that moves back and forth like a sea-saw based on differential pressure. As a result, the linear motion of this magnetic piston pushes and pulls a rotary magnet that connects to the pointer. It gives a “magnetic rack and pinion” output-signal.

The following measurements can be taken using DP gauges.

1. Monitoring for contaminated filters
2. Checking the bag closure in the dust collector for bags
3. Clean room over pressure measurement
4. Gaseous and Liquid Media Flow Measuring

## Function of a differential Pressure Gauge

Differential pressure gauge consists of two sealed medium chambers. The two chambers are separated by measuring the elements. If both chambers have the same pressure, the measuring elements do not experience pressure, and the DP gauge shows no deflection.

Different pressure elements such as diaphragm element, capsule element, Borden tube, etc. are used in DP gauge. This enables a scale range from 0 – 0.5 mbar to 0 – 1,000 bar.

If there is a pressure difference between the two chambers, the pressure exerted on one measuring element is greater than the pressure exerted on the other chamber element. In this case, the DP gauge shows deflection.

When static pressure is high, we can directly measure the low differential pressure. The diaphragm element provides a high overload capacity. The maximum static pressure and overload capacity should be observed on the L and H side. The movement of the measuring element and the transmission of the pressure signal are the same as with the over pressure gauges already described in most cases.

The scale ranges are between 0~16 mbar and 0~25 bar in accuracy classes from 0.6 to 2.5.

## Area Of Application

1. Monitoring filter health
2. Flow Rate Measurement
3. Detecting Scale Buildup
4. Detecting Leaks
5. Filling level measurement (in enclosed containers)

## Use of Differential Pressure Gauge

Differential pressure gauge can be used in many applications-

### Monitoring Filter Status Using Differential Pressure Gauge

As the filter cartridges become clogged, the DP between the inlet and outlet increases due to a build-up of contaminants in the filter mesh. Because of this, operators can measure a differential pressure drop across a filter and get a visual indication of how dirty their filter systems are. Consequently, a filter application can use a DP gauge for:

1. Help operators prevent damage to their systems as they stay informed of filter status.
2. Prevent legal issues between filter manufacturers and customers who end the life of their filters and abuse the system
3. Increase filter cartridge sales by 20-30% by helping customers stay informed about filter status

### Flow Rate Measurement Using a Differential Pressure Gauge

Bernoulli’s principle states that an increase in the speed of a fluid is accompanied by a decrease in pressure or a decrease in the potential energy of the fluid. As a result, instruments known as venturis have been used for years to measure flow rates by detecting this change in pressure. As a result, and the operator can connect the higher pressure side of the differential pressure gauge to the upstream and the lower pressure side of the differential pressure gauge to downstream, a flow rate can be measured. In addition, a differential pressure gauge can be used in flow rate applications:

1. Provide direct feedback of flow rate
2. Be the most robust solution that lasts for years and outperforms electronic alternatives

### Measuring Liquid Using a Differential Pressure Gauge

Standard pressure gauges cannot be used to measure the liquid level in a cryogenic tank due to a number of issues. Most importantly, the tanks are pressurized (often above 500psi) and standard pressure gauges mounted on the bottom will measure the liquid level and tank pressure. Consequently, a differential pressure gauge must be used by connecting the high side to the bottom of the tank and the lower side to the top of the tank. As a result, tanks that measure liquid oxygen, nitrogen, argon, and more can be a cost-effective solution to take an inside looks at their liquid levels. These applications of differential pressure gauges for cryogenic liquid levels can:

1. Provide liquid level in pressurized tank
2. Provides added value to microbulk storage tanks

### Detecting Leaks Using a Differential Pressure Gauge

Probably one of the least understood applications of DP gauges involves the detection of leaks in systems. By comparing a reference vessel to a vessel with a potential leak, a differential pressure can be measured and the leak detected. As a result, there is a huge saving of time and the results are far more accurate than the hours waiting for a drop on a standard pressure gauge. Due to the fact that differential pressure gauges can accurately measure up to 0.1″ H2O, you will be waiting much less! In addition, differential pressure gauges can be used in leak detection applications:

1. Simple and Cheap