Frequently Asked Questions

Mercotac® Brushless Slip Rings

Do you want a superior connection, or an ordinary slip ring? The choice is yours. These Frequently Asked Questions explain the benefits of Mercotac brushless slip rings.

Mercotac products are trusted by numerous companies worldwide across a broad range of applications. For more detailed information, please refer to our Technical Info. and Applications pages.

General FAQ:

For customers located in the United States, please contact Mercotac directly. Orders may be placed over the phone at (760) 431-7723 or email

For customers located outside of the United States, please find the distributor for your area via our ordering page.

All standard models of Mercotac brushless slip rings are maintained in stock in reasonable quantities at our factory in Carlsbad, CA, USA. Normal shipping is done via UPS Ground, with delivery times ranging from one to five business days depending on the distance from Southern California. Need faster shipping? Please contact us to inquire about expedited shipping options.

In short, as Mercotac brushless slip rings are industrial parts, they may be legally bought and sold in Europe for non-consumer applications. For further detailed information, please see our EU Directives page.

Our technical support team is always willing to assist you in finding the perfect Mercotac that meets your specifications. Please reach out to or submit an inquiry via our contact form.

Disclaimer: The above information is correct to the best of Mercotac's knowledge and is for information purposes only and should not be relied upon as legal advice.

Technical FAQ:

Mercotac brushless slip rings employ a unique design principle that sets them apart from traditional sliding, brush-type slip rings. Instead of using brushes to establish contact, the connection is made through a pool of liquid metal that is molecularly bonded to the contact points. This design provides a stable, low-resistance connection that does not wear down with rotation. There are many reasons why Mercotac products are superior to traditional slip rings:

  • NEAR ZERO NOISE: Unlike brush-type slip rings, Mercotac products produce very little electrical noise due to their innovative design.
  • LOW RESISTANCE: The resistance through the rotating contact is less than one milliohm, which is much lower than what you would get with a brush slip ring.
  • NO SIGNAL DEGRADATION: Mercotac products maintain signal integrity over time, whereas brushed slip rings can degrade the signal.
  • NO MAINTENANCE: Brushed slip rings require regular maintenance, but Mercotac brushless slip rings are maintenance-free.
  • COMPACT & AFFORDABLE: Mercotac products are more compact and cost far less than traditional slip rings with the same capacity. For a more detailed explanation, you can watch the video at the top of this page.

Yes. Mercotac products are ruggedly constructed, utilizing a sealed ball bearing in a black anodized aluminum body. The electrical connections are silver-plated brass or copper for low resistance. The larger Mercotac's have white mounting bushings on both ends made of insulating plastic, which are potted with epoxy. Mercotac products are both durable and compact.

Yes, Mercotac brushless slip rings are not only suitable for regular current and voltage applications but also for low voltage and low amperage current applications, as well as various types of signals. Unlike standard brush slip rings, Mercotac's use liquid metal as a conductor, resulting in an extremely low noise signal transmission that is comparable to the signal transmitted through a solid wire. This makes Mercotac electrical slip rings superior to brush slip rings for signal and data transmission. With Mercotac products, the signal quality does not degrade, and no maintenance is required.

To select the appropriate Mercotac Brushless Slip Ring for your application, it's essential to consider the number of conductors, voltage, amperage, and RPM requirements. These factors play a significant role in determining the ideal Mercotac model for your needs. Here are the steps for how to choose a Mercotac Brushless Slip Ring in a step-by-step format:

  1. Start by determining the number of conductors you need.
  2. Investigate your application to determine the maximum current and voltage required.
  3. Devise a mounting strategy with the help of our technical pages.
  4. Consider other requirements, such as maximum torque or if the application is in a harsh environment. Many units are available in low-torque configurations and/or Stainless-steel options with a sealed bearing.
  5. Use the Mercotac website along with this information to choose the unit that is right for your application. Review the specification page or the product pages' specifications to determine the required unit for your application, including RPM requirements.
  6. For most applications, these steps will suffice to determine the unit you need. However, if you have specific considerations such as extremely high voltage or current or a different number of conductors, please contact our technical adviser for assistance.

Mercotac brushless slip rings are designed for mounting to the end of the rotating axis either in a vertical or horizontal orientation. The mounting method depends upon the Mercotac model.

The larger Mercotac products typically are mounted into a hollow shaft or collar on the end of the rotating device either by the plastic bushing or the body. The Mercotac may be held in place with a setscrew or a slotted clamp system.

The smaller Mercotac products plug into the electrical receptacle and use this both as the mounting and electrical connection. These receptacles are knurled and designed to be press fitted into a hole on the end of the rotating device.

Eccentricity of the mounting should be less than .005” TIR (total indicated runout).

The preferable method of mounting the Mercotac is with the black body rotating. Both ends of the Mercotac should not be rigidly mounted; one end needs to float free. If needed, a floating torque arm may be used to prevent the stationary end from rotating.

Please note that Mercotac products are not designed to support any axial or torsional load.

Please see the Mounting page and/or Downloads page "Service Instructions" for more details.

No, Mercotac products cannot be used upside-down. They are designed with a top and a bottom. An arrow on the side of each unit specifies the top. A vertical mounting would position the Mercotac with the arrow pointing up. Mercotac products can be mounted at vertical or any angle between vertical and 90 degrees horizontal. This allows for nearly any mounting orientation that would be required. They cannot, however, be mounted with the arrow pointing below horizontal or upside-down.

Yes, in special circumstances. In the case of a vertical mounting (or a mounting somewhat vertical) where the Mercotac unit needs to be mounted below the rotating device, the Mercotac will need to be attached by the upper bushing into the mounting shaft or collar. In this case the body and lower bushing will be stationary and free floating. It is very important that the mounting be straight and centered so there is zero or minimal lateral motion or wobbling of the body, less than .005-inch TIR is recommended. The connecting wire must be fully supported so as not to add axial or torsional loads at the Mercotac.

All the larger Mercotac products with tab connections are supplied with push-on disconnects. Some Mercotac products have terminal blocks for connecting wires. The smaller Coaxial Mercotac models use plugs that are available separately for each model to which customer wires may be soldered. When connecting wires to the stationary floating end of the Mercotac allow sufficient length so as not to pull on the connection. Do not attempt to solder wires directly to Mercotac terminals; this will damage interior parts causing the Mercotac to fail, and void the warranty. The warranty can be found in the Service Instructions on the Downloads page.

No. Attempting to solder wires directly to a Mercotac will overheat and damage the internal parts, causing product failure and void the warranty. The warranty can be found in the Service Instructions on the Downloads page. Appropriate disconnects are available for Mercotac products and should always be used.

No. Because the design of the small Coaxial Mercotac products is unique, standard industry plugs cannot be used. Accessory plugs are available from Mercotac Inc.

If you need more than eight conductors, don't worry – Mercotac has options for you. The Versatac™ product line offers a range of units with 2 to 22 conductors, so you can find the right fit for your needs. If the unit won't work for your application, there are other options to consider. While the eight-conductor Mercotac model is the largest unit available, you can increase the number of conductors by using two Mercotac products if you have access to both ends of the rotating axis. This would provide a maximum of sixteen conductors. Alternatively, you can combine a Mercotac with a standard slip ring that has a hole in the center. The Mercotac would handle the sensitive signal connections, while the brush-type slip ring could be used for power connections. With these options, you can be sure to find a solution that meets your needs.

Mercotac brushless slip rings are constructed of corrosion-resistant materials, but their suitability for use in damp or corrosive environments depends on the severity of the conditions. They are not recommended for use in wet environments without protection. However, Mercotac products are available with a stainless-steel ball bearing for use in damp or corrosive environments. For additional protection, we recommend using the "Boot Kit" accessory with larger models, which can increase the IP protection rating of the Mercotac to IP51. If you are unsure whether a Mercotac slip ring is suitable for your specific environment, please consult with our technical support team.

No, Mercotac products cannot be used in a vacuum. This is because Mercotac products contain liquid substances that could cause out-gassing and create internal pressure in a vacuum environment. This pressure would cause increased rotational torque and could potentially lead to failure of the unit. If you require a slip ring for use in a vacuum environment, please contact our technical support team for guidance on suitable alternatives.

Mercotac products are covered by a one-year warranty from the date of delivery. The warranty can be found in the Service Instructions on the Downloads page. The actual life expectancy of a Mercotac brushless slip ring depends on several application-specific factors, such as vibration, temperature, RPM, mounting eccentricity, and other factors, which make it difficult to predict with accuracy for all applications. However, under controlled test conditions, Mercotac products have been shown to last for more than a billion revolutions. In real-world applications, Mercotac slip rings can typically provide years of trouble-free service if all other specs are within tolerances and there is no excessive vibration. Additionally, Mercotac slip rings are maintenance-free.

Vibration or sudden movement can significantly shorten the life of the Mercotac or even cause failure. Vibration moves the liquid metal conductor away from the contact area, which can cause open or shorted channels. If vibration is present in the application, a vibration-isolating mounting should be used to mount the Mercotac.

Currently, we do not offer any Mercotac brushless slip ring models with a pass-through hole in the center. However, we have provided custom solutions with a center hole in the past. The design of Mercotac brushless slip rings prioritizes compactness for easy mounting at the end of a rotating axis, making them more durable and cost-effective. If you have specific requirements that include a center hole, please contact our technical support team for guidance on suitable alternatives or custom solutions.

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.

See related questions:
How are Mercotac brushless slip rings mounted?
Can a Mercotac brushless slip rings be mounted by the upper brushing?

No. Mercotac's contain elemental mercury which is regulated by the European Union's Restriction of Hazardous Substances (RoHS). However, this directive does not prohibit the import and sale of industrial parts because it only covers consumer electrical and electronic products. Therefore, Mercotac products may still be legally bought and sold in Europe and elsewhere in the world for non-consumer applications. (See our explanation page EU Directives.)

Disclaimer: The above information is correct to the best of Mercotac's knowledge and is for information purposes only and should not be relied upon as legal advice.