The dial indicator seems simple on the surface, but it plays a crucial role in the testing of soils, concrete, and materials. Widely used by construction experts, engineers, and artisans to assess comparative height, the dial indicator provides reliable results with exceptional accuracy. But before we get into everything the dial indicator can do, let’s take a step back and look at how it works. In this blog, we’ll answer the question, “what is a dial indicator,” ways to use it, and how to read one. We’ll also give you our recommendations on the best dial indicators available for all your material testing needs.
Dial indicators (also known as drop indicators, dial gauges, or runout gauges) are measuring instruments that react to contact pressure and amplify small displacements on a surface to provide measurable results. Dial indicators are great at measuring small displacements.
Suppose you were trying to measure the deviation between two surfaces with a height difference of 7mm (0.27 inches). In that case, you’d struggle to get precise measurements with rulers or calipers. With an indicator, you could achieve an accurate measurement of this height change every single time. Dial indicators can be either analog or digital. Most analog types accurately measure small distances to the nearest ±0.008mm. The digital types of gauges are even more accurate, measuring in the range of ±0.005mm. This type is considerably more precise and less prone to human error. That said, because the analog is easy to use, fast to set up, and doesn’t need batteries, it is still popular in many industries.
Dial indicators are available in various measurement ranges to accommodate different applications. The most common ranges are 0-1 inch (0-25.4mm) and 0-2 inches (0-50.8mm). Understanding the measuring range is crucial for selecting the right indicator for your specific needs. That said, some smaller, specially designed dials may only measure height deviations up to 0.5 inches (12.7mm), 0.025 inches (6.35mm), or 10 millimeters.
These ‘mini’ dials are used when a high degree of precision is required, such as in fine machining, watchmaking, or the jewelry industries. We always use dial indicators in conjunction with other tools because they are too sensitive to use by hand. A magnetic base can hold them in place and ensure that measurement results are always reliable and accurate.
What does a dial indicator measure?
Dial indicators measure the comparative height difference between two surfaces. People rarely use them for direct height measurements. For example, if you wanted to measure the height of a metal bracket for use in construction, a height gauge would give you a faster, simpler absolute height measurement. However, when calculating the comparative height of two metal brackets, a dial indicator would be a more precise way to measure the difference. By setting the zero point on the dial indicator, you can ensure accurate and consistent measurements.
What is a dial indicator used for?
To give you a better understanding of how a dial indicator works in practice, here are a few common applications for the tool. A lever dial indicator is a popular and commonly used type of dial indicator, perfect for measuring small linear and geometric features on a component.
What is a dial indicator used for in concrete compressive strength tests
Dial indicators are commonly used in compressometers for concrete compressive strength tests. They accurately assess the average deformation of concrete cylinders when subjected to stress.
What is a dial indicator used for in consolidation testing in soil
Dial indicators are useful when testing for consolidation in soils. Once the soil saturates and expands, the indicator can accurately measure the deformation and settlement of the sample to provide information about the soil’s properties.
What is a dial indicator used for in checking spindle runout in machines
People commonly use a dial indicator to measure spindle runout in machines. This instrument provides precise measurements of any deviations or wobbling in the spindle. The tester places the indicator horizontally and rotates the spindle. The indicator records runout, enabling the tester to make adjustments and align the spindle.
What is a dial indicator used for in assessing surface roughness
The dial indicator is an excellent way to assess the roughness of a surface. For example, you could use the indicator to evaluate the surface finish quality of a casting.
The key components of a dial indicator
To learn what is a dial indicator used for, let’s first explore its key mechanical components. A dial gauge, often used interchangeably, shares similar construction and calibration processes.
Case: This refers to the outer case that surrounds it. After positioning the indicator correctly, you can rotate the case to zero the needle. This is an essential step in the calibration process.
Needle/pointer: The needle is located in the center of the indicator. The needle rotates clockwise when pressure is applied to the contact point and counterclockwise when the pressure is released. The needle points to a graduated scale, which people use to obtain the final comparative height measurement.
Graduated Scale: The case contains a graduated scale closely resembling a clock face. In most dial types, the scale increases in increments of 0.01mm, and one complete revolution of the needle represents 1mm of pressure applied to the contact point.
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Revolution counter: The dial indicator also contains a much smaller scale known as the revolution counter. This scale counts the number of pointer revolutions in the outer scale. Each number on the revolution counter represents one total rotation (1mm).
Plunger: The plunger, attached to the spindle, is spring-loaded and fully extended when not in use. The plunger retracts when pressure is applied, causing the needle to spin clockwise. If the plunger retracts by 1mm, this measurement appears on the graduated scale, enabling the tester to measure height displacement accurately.
Contact point: The contact point touches the surface being measured and is connected to the plunger. Â Different contact points are available for different applications. For instance, extended contact points give the indicator a longer reach, which can be useful when testing certain materials.
Mounting stem: The mounting stem (or mounting lug) attaches to other pieces of equipment, like a magnetic base. Attaching the indicator to a stable base is essential for achieving accurate measurements.
What is a dial indicator and how does it work?
The basic premise behind the dial indicator is quite simple. The reading on the indicator is dependent on the upward and downward movement of the plunger. The plunger extends fully when not in use. It retracts into the mounting stem once you apply pressure to the contact point. This causes the outer scale to spin clockwise. When pressure is released, the outer scale spins counterclockwise. To understand how an indicator measures comparative height, we need to discuss its practical application.
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Let’s say you have a flat rectangular plate that requires the same exact height on each side for proper functionality. You can use a dial indicator to ensure the surface is completely level.
Here’s how to do it.
1) First, position the plate on a stable surface and attach the dial indicator to a base to secure it.
2) Then, lower the dial indicator until the contact point reaches one side of the plate. Allow the plunger to retract slightly.
3) Now that the dial indicator is in place, rotate the case to align the zero mark on the graduated scale with the needle’s current position.
4) With the indicator secured at a fixed height, slowly move the rectangular plate to position the contact point over the opposite side. If the surface is entirely level, there should be no change. If the needle spins clockwise, this means that the new side is higher than the one you started on. Although, it spins anti-clockwise, the new side is lower than the one you started on.
5) You can then use the graduated scale to assess the comparative height difference between the two sides. For example, let’s assume that the needle span clockwise from 0 to 0.7mm from side one to side two. This would tell us that side two is 0.7mm higher. As you can see, there’s no need to know the absolute height of the rectangular plate to assess whether it’s completely level. All that matters is the difference between the two sides.
How do you read an analog dial indicator?
Reading an analog dial face is quick and easy. To do so, simply add the number from the revolution counter to the measurement displayed on the outer graduated scale. For example, let’s say your plunger retracts 17.35mm when coming into contact with a surface. We know that each complete revolution of the needle represents 1mm and that each time the needle revolves, the revolution counter increases by 1. Therefore, a measurement of 17.35mm appears as 17 on the revolution counter and 0.35mm on the outer graduated scale.
What is a Dial Indicator vs. dial test indicators: What’s the difference?
Dial indicators, also known as drop indicators, differ from dial test indicators despite some similarities. It’s easy to confuse the two, and searches might sometimes yield information about the test indicator. However, there are clear differences between them. The primary distinction is that the indicator has a contact point attached to a lever that can move at an angle, while the test indicator features a spring-loaded plunger that moves only up and down.
Dial indicators provide more precision than other types and often convert tiny lateral movements into measurable readings. They have a highly sensitive mechanism and a small measuring range, making them ideal for projects that require precise alignments or checking for concentricity. These indicators are excellent for measuring small displacements between two surfaces with high accuracy. However, these indicators are not suitable for larger measurements in the range of 1-2 inches because they lack a spring-loaded pointer. In contrast, the dial test indicator’s spring-loaded plunger extends and retracts automatically, providing simple, fast, and precise measurements, even for height changes above 1 inch.
Summary of What is a Dial Indicator
If you’re looking for high-quality dial indicators for your next material test, look no further than CertifiedMTP. We offer a range of best-in-class indicators from industry-leading manufacturers like Gilson Company and Karol-Warner. Whatever your material testing needs, we have an indicator for you.
We design our products, including length comparators, compressometers, strain gauge sets and flowmeters, to deliver accurate and reliable results consistently. If you’re looking for something else, feel free to get in touch; we’re always happy to help.