Technical Info

Welcome to Mercotac's Technical Information page, your resource for information on Mercotac Brushless Slip Rings. These slip rings provide advanced rotary connections with superior performance compared to brush-style slip rings by eliminating electrical noise in signal transmission. With a resistance below one milliohm and a maintenance-free design, Mercotac connectors provide reliable and long-lasting performance. They outlast brush-type slip rings, withstanding billions of revolutions. Despite their exceptional performance, Mercotac Slip Rings are also cost-effective, making them the ideal choice for applications that demand noise-free power and signal transmission. Explore our Technical Info to learn more about the advantages and applications of Mercotac Brushless Slip Rings.

The Mercotac Advantage:

Brush-type slip rings introduce electrical noise into the transmitted signal due to the variation in resistance when rotated. As you can see here, compared to typical slip rings, the Mercotac Brushless Slip Rings transmit with nearly zero electrical noise; thus, the same slip ring can be used for both power and signal transmission.

Typical initial electrical resistance through a brush-type slip ring is 10 to 20 milliohms and will fluctuate as it turns. The resistance through a Mercotac Brushless Slip Ring is approximately one milliohm and constant, plus it will not vary over the longer life of the slip ring. This superior performance is possible because of unique design features of Mercotac products. The electrical conduction path is a small pool of liquid metal that is molecularly bonded to the contacts, creating a connection that is constant and unchanged for the life of the Mercotac.

Other desirable features of Mercotac products are: long life, increased reliability, no maintenance required, durable, compact, low cost, and they are made in the U.S.A.

Unlike brush-style slip rings, Mercotac Brushless Slip Rings do not introduce electrical noise to the signal...

Oscilloscope Image

Advantage One: Extremely low electrical noise
Advantage Two: Less than 1 milliohm of resistance
Advantage Three: No wear, zero maintenance

Advantage Four: One brushless slip ring for signal and power
Advantage Five: Much longer life
Advantage Six: Lower cost

Mercotac Brushless Slip Rings offer many advantages over traditional brush-style slip rings. Here are some ways Mercotac Brushless Slip Rings make superior connections:

  1. NEAR ZERO NOISE: Technical Image Brush-Type Slip rings introduce electrical noise into the signal being transmitted. Mercotac Brushless Slip Rings transmit with nearly zero electrical noise, thus the same brushless slip ring can be used for power and signal transmission.
  2. LOW RESISTANCE: Typical resistance through a slip ring is 10 - 20 milliohms. The resistance through a Mercotac is less than one milliohm due to the unique liquid metal wetted contacts.
  3. MAINTENANCE FREE: Brush Slip rings require maintenance and lose signal quality over time due to brush wear and debris. Mercotac Brushless Slip Rings are maintenance free, do not degrade the signal over time and last much longer than brush-type slip rings.
  4. LONG LIFE: Brush-Type Slip rings typically last several million revolutions. Mercotac Brushless Slip Ring revolutions frequently approach a billion to multiple billions of revolutions under controlled test conditions. Many Mercotac models that were installed decades ago are still in use today.
  5. LOW COST: Though superior in performance and durability, Mercotac Brushless Slip Rings cost less than slip rings of comparable capacity. The above superior performance is possible because of the unique design feature of Mercotac Brushless Slip Rings: the electrical conduction path is a liquid metal that is molecularly bonded to the contacts. This creates a connection that is constant and unchanged for the life of the unit.
  6. HIGHER MAXIMUM SPEED: Mercotac products typically offer higher RPM’s than a brush type slip ring.

We compared the Mercotac Model 430 Brushless Slip Ring with three other slip ring brands from the USA. The comparison is based on specifications such as the number of contacts, contact resistance, price ratio, maintenance interval, life cycle, speed RPM, voltage and amps range. A real-life example of a laminating machine operating one eight-hour shift per day, five days a week, is also used to compare maintenance costs and lifetime. The chart shows that the Mercotac® 430 Brushless Slip Ring is the preferred choice where longevity and reliability is required, all at a lower cost.

Comparison of Three Quality Slip Rings to Mercotac® Model 430

Mercotac ®
Slip Ring
Brand #2 U.S.A.
Slip Ring
Brand #3 U.S.A.
Slip Ring
Brand #4 U.S.A.

No. of Contacts
4 4 4 4

Resistance (Ω)

.001* .0125 .008 na

Price Ratio
1* 2.7 x 3.5 x 3.6 x

Interval / Revs.

No Maintenance 500,000** 500,000 500,000**

Life Cycle in

500,000,000+ 50,000,000 6,000,000 10,000,000

Maximum Speed

1200* 100 500 125

Voltage Range (V)

0-250 120-300 0-150 0-600

Amps Range (A)

0-30 0-40 0-5 0-35

Real Life Example
Based on a laminating machine operating one eight hour shift per day, five days per week.

Maintenance Cost
Over Lifetime*

Zero $4,935 $588 $994

Lifetime* (months)

144 47 5.6 9.5

Maintenance &
Purchase Price

1.0 41.4 x 8.1 x 11.5 x

** Industry recommended intervals, 500,000 revolutions or 6 months.

* Maintenance labor calculated at $50 per 45 min. maintenance interval and does not include any lost opportunity costs. Lifetime is based on 100 RPM for all slip rings.

Critical Specifications in Chart showing Mercotac® superiority

  • Technical Image Contact Resistance: The extremely low contact resistance of Mercotac® Brushless Slip Rings allows them to transmit low voltage signals without distortion which is not possible with slip rings.
  • Price: The significantly lower cost of Mercotac units makes them usable in many applications where slip rings would be economically unfeasible.
  • Maintenance: The zero maintenance of Mercotac Brushless Slip Rings reduces customer labor costs significantly as well as reducing costs of lost production, making them much more affordable than brush type slip rings.
  • Life Cycle: The long life cycle of Mercotac Brushless Slip Rings makes them more efficient and affordable than brush type slip rings which need replacing much more often. The type of application can cause variations in the life of Mercotac's but many last longer than 500,000,000 revolutions. Customers have reported units with over 1 billion revolutions.
  • RPM: The higher RPM specification of Mercotac Brushless Slip Rings allows them to be used in applications where brush type slip rings will not work.

Technical Image
Top mount to body. (preferred)

Mercotac Brushless Slip Rings are mounted on rotating axes or shafts, in either a vertical or horizontal orientation.

Larger models are mounted into a hollow shaft or collar adapter using a setscrew or slotted clamp system, while smaller models plug into an electrical receptacle.

The Versatac model offers both shaft and flange mount options, with the latter requiring a mating flange and not allowing body mounting.

To prevent premature failure, eccentricity should be less than .005” TIR or FIM, and the slip ring should not be subjected to axial or torsional loads or side loads. Use vibration isolation mounting for equipment subject to vibrations or sudden movements.

The Mercotac has a laser-etched UP arrow for vertical mounting, which can be mounted at any angle between vertical and 90 degrees horizontal.

Learn more on our Mounting page.

Remember when Mounting:

  • Mercotac Brushless Slip Rings cay be used in any position between vertical and 90 degrees horizontal. The UP arrow should not point below horizontal.
  • In horizontal applications, mount the Mercotac with the body rotating to reduce mechanical loads on the bearing.
  • Limit mounting eccentricity to a maximum of .005” TIR.
  • Mercotac products are not designed to carry mechanical loads. One end should be allowed to float, attached only by the connecting wires.
  • The connecting wires on the stationary end should have enough extra length (looped) so as not to pull or put a side load on the Mercotac.

Service instructions are available to download for both small and large models:

Technical Image Our service instructions explain the correct way to use our products. These instructions can be found on our Downloads page.

It is important to operate and handle Mercotac products according to our manufacturer guidelines, service instructions, and within product specifications. If products are not operated as instructed it could cause failure and void the warranty. The warranty can be found in the service instructions.


Here are some takeaways of DOs and DON'Ts for using and handling Mercotac Brushless Slip Rings:

Green CheckDOs:

  1. Use the Mercotac horizontally or vertically with the "UP" arrow pointing above horizontal.
  2. Mount the Mercotac with the body rotating to reduce mechanical loads on the bearing and internal components.
  3. Use stranded wires of ample length and flexibility to avoid mechanical loads.
  4. Provide quick acting current protection on wires attached to the Mercotac.
  5. Use the recommended crimp tool for secure crimping of the terminals.
  6. Use shock isolating mounting, such as rubber tubing, in installations that require it.
  7. Provide thermal insulation where necessary to prevent overheating.

Red XDON'Ts:

  1. Do not dispose of the Mercotac improperly. Be environmentally responsible and recycle through Mercotac Inc.
  2. Do not solder to the Mercotac or bend tabs excessively.
  3. Do not rigidly mount both ends of the Mercotac.
  4. Do not use wires that pull on the Mercotac or allow too much free play.
  5. Do not use the Mercotac for carrying mechanical loads.
  6. Do not work around a Mercotac without disabling the power source.
  7. Do not handle a suspected failed Mercotac without disabling the power source.
  8. Do not use the connector without proper protection in food packaging applications.

Guidance for using Mercotac® Brushless Slip Rings in engineering designs.

You understand the critical role of reliable electrical connections in your designs. Mercotac recognizes this and is dedicated to offering innovative solutions that provide superior performance and durability. In our Learning Center we provide valuable details for our engineer and technical customers, including the key benefits and features of our brushless slip rings, internal materials, component details, and installation tips. Whether you're designing a new project or seeking a replacement part, our goal is to equip you with the knowledge necessary to make informed decisions about our products.

Click on the pictures to access these learning center pages:

Guidance for using Mercotac® Brushless Slip Rings in engineering designs.

Learning Center Construction & Materials

Learn about our Mercotac® Construction & Materials: Body Materials, Bearing Types, Conductors/Terminals, Thread Sizes, Mounting Options.
Learn More

Learning Center Electrical Characteristics

Learn about Mercotac® Electrical Characteristics: Voltage Rating, Current Rating, Contact Resistance, Circuit Separation, Operating Temperature, Frequency.
Learn More

Learning Center Rotational Characteristics

Learn about Mercotac® Rotational Characteristics: Rotational Speed, Rotational Torque.
Learn More

How does a Slip Ring work?

Technical ImageA slip ring is an electrical device used to transmit current or signals between a stationary wire and a rotating device. It consists of a stationary brush that makes contact with the rotating metal ring, conducting the current or signal through to the device. Multiple ring/brush assemblies can be stacked along the axis for multiple circuits. Slip rings have been used for decades as a basic means of transmitting current to a rotating device. They are also known as collector rings, rotary electrical contacts, and electrical slip rings. While some people may use the term "commutator" interchangeably, commutators are specialized for use on DC motors and generators and differ somewhat from slip rings.

Question # 1 on our FAQ Page describes how Mercotac® Brushless Slip Rings are different from and superior to traditional brush-style slip rings. Many industries have found the superior performance of Mercotac brushless slip rings to be the answer for their slip ring assembly problems and requirements. Click here to see video clips demonstrating the Mercotac® brushless slip ring in action.

View our Products

Mercotac® is a leading provider of brushless slip rings that offer superior performance compared to traditional slip rings with brushes. They require no maintenance and are an ideal solution for industries that utilize slip ring assemblies.

In fact, either end can be attached to the rotating device. It is preferable to mount the Mercotac so that the body rotates. The body and lower bushing are pressed together as one unit. The upper bushing (as identified by the "UP" arrow on the body) is mounted to a ball bearing and turns independently of the body. Please see the rotating model to the left which shows the body and lower bushing rotating with the upper bushing stationary. If a unit needs to be mounted vertically, below the rotating device, then mounting the Mercotac by the upper bushing with the body floating stationary is acceptable.

Technical ImageMercotac offers compact and cost-effective brushless slip rings that can transfer power, signals, and data through a single device. These products are made in the USA and readily available in stock

Our complete Product Line can be viewed online.

Or, you can download our Product Catalog as well as information on our Coaxial and Modular Series Applications.

For Ordering Info, Click Here.

The word commutator is sometimes mistakenly used in place of the general term slip ring. A commutator is a specialized slip ring typically used on Direct Current motors and electrical generators to transfer electrical power between the stationary housing and the rotating armature with the added purpose of reversing the electrical current direction.

A commutator ring is made of insulated metal segments unlike the solid metal ring of a slip ring. Electrical brushes (contacts) rub on this rotating ring to make the electrical connection. These ring segments are wired with the ability to reverse the electrical current. In a DC motor this switching reverses the magnetic field to keep the motor turning. In a generator the switching changes alternating current into current flowing in one direction (DC).

Here is a picture of a commutator with the housing for the brushes disassembled from the rotating copper ring for visual purposes:

Technical Image

Some people use the term commutator for slip rings, however commutators are somewhat different and are specialized for use on DC motors and generators. Mercotac brushless slip rings cannot be used as commutators because they don’t allow for reversing the electrical current.

Technical ImageMercotac slip rings are used in a diverse range of industries and applications to transfer power and signals to rotating components. These slip rings are commonly found in wind turbines, cable reels, robotics, packaging machinery, semiconductor manufacturing equipment, medical equipment, and industrial machinery. They are also used in many rotary motion control applications. The Applications page on the Mercotac website provides examples of the various ways in which Mercotac slip rings are used and highlights the benefits they offer, such as reliability, durability, and the ability to handle high-speed and high-frequency signals. This resource can be useful for engineers who are interested in learning about how Mercotac products can meet their design needs.

Check out our videos of Mercotac Brushless Slip Rings in action

The model train is powered through the small Mercotac coaxial brushless slip ring in the center of the table.

Below, power is transmitted to the light inside the rotating roller while simultaneously the thermocouple temperature signal from inside passes out through the Mercotac brushless slip ring to the LED readout. This models a typical heated roller application for packaging, printing, and laminating equipment.

An oscilloscope compares the signal noise after passing through the Mercotac brushless slip ring with a traditional brush type slip ring shown below. Learn More

What can we help you with next?

Learning Center Rotational Characteristics

How to Order Mercotac® Products: Order directly from Mercotac from within the USA, or through an authorized distributor if outside of the USA.
Learn More

Learning Center Slip Ring

Find Which Slip Ring You Need: Replace your brush or precious metal slip ring with superior Brushless Slip Rings from Mercotac.
Learn More

Learning Center Products

Frequently Asked Questions: Learn about the benefits of Mercotac products. We strive to answer all of your brushless slip ring questions.
Learn More