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Want superior connection, or an ordinary slip ring? The choice is yours. These Frequently Asked Questions explain the benefits of Mercotac's "electrical slip ring".

1. Why is a Mercotac rotating connector superior to a slip ring?
2. Are Mercotac connectors made of durable materials?
3. Can Mercotac connectors be used for low voltage signal, data, thermocouple & strain gauge circuits? 
4. How do I select the right Mercotac connector for my application?
5. How are Mercotac connectors mounted?
6. Can Mercotac connectors be used upside down?
7. Can a Mercotac connector be mounted by the upper bushing?
8. What type of wire connections are needed?
9. Can I solder wires to the Mercotac connector?  
10. Can standard industrial coax plugs be used on Mercotac Coaxial series connectors?
11. What if I need more than eight circuits? 
12. Can Mercotac connectors be used in damp or corrosive environments?
13. Can Mercotac connectors be used in a vacuum?
14. How long can I expect a Mercotac connector to last?
15. How does movement or vibration in my machine affect the Mercotac connector?
16. What is the usual delivery time once an order is placed?
17. Do you offer any with a hole in the center?
18. What part rotates?  
19. Are Mercotac connectors RoHS compliant?
20. Additional Information on slip rings and Mercotac connectors


  1. Why are Mercotac® rotating connectors superior to slip rings?
    Mercotac rotating connectors use a unique design principle unlike the sliding, brush contact of a slip ring. The connection is made through a pool of liquid metal molecularly bonded to the contact, which provides a low resistance, stable connection. When there is rotation the fluid maintains the electrical connection between the contacts without any wear. The following are among the many reasons why Mercotac connectors are superior to slip rings. First, unlike a slip ring, Mercotac connectors produce near zero electrical noise due to their unique design. Second, resistance through the rotating contact is less than one milliohm, which is much lower than the resistance of a slipring. Third, Mercotac connectors do not degrade the signal over time, which does happen with slip rings. Fourth, slip rings require maintenance and Mercotac connectors are maintenance free. Fifth, Mercotac connectors are more compact and cost far less than slip rings of equal capacity. Read More & See Video Explanation  (top)

  2. Are Mercotac® connectors made of durable materials?
    Yes. The Mercotac connector is 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 white mounting bushing on both ends of the larger Mercotac connectors is insulating plastic potted with epoxy. Mercotac connectors are very durable as well as being compact. (top)

  3. Can Mercotac® connectors be used for low voltage signal, data, thermocouple and strain gauge circuits?
    Yes. In addition to normal current and voltage uses, Mercotac connectors are ideally suited to low voltage/low amperage current and signal transmission. Unlike standard brush slip rings, Mercotac connectors use liquid metal as the conductor. This produces an extremely low noise signal transmission similar to the signal transmitted through a solid wire. This makes Mercotac connectors superior to brush slip rings for signal and data transmission. The signal quality does not degrade and no maintenance of the Mercotac connector is required. (top)

  4. How do I select the right Mercotac® connector for my application?
    The number of conductors, voltage, amperage, and RPM will determine which model of Mercotac connector needed. First, decide the number of conductors needed. Next, consult the specification page to determine if a Coaxial or Modular unit will meet your amperage, voltage, and RPM requirements. Please note: Even though the larger Mercotac connectors are rated for 30 amps they work equally well for signal applications (top)

  5. How are Mercotac® connectors mounted?
    Mercotac rotating connectors are designed for mounting to the end of the rotating axis either in a vertical or horizontal attitude. The mounting method depends upon the Mercotac model. The larger Mercotac connectors 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 connector may be held in place with a setscrew or a slotted clamp system. The smaller Mercotac connectors 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 runnout). The preferable method of mounting the Mercotac connector 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 connectors are not designed to support any load. Please see Literature page for downloadable "Service Instructions" for more details. (top)

  6. Can Mercotac® connectors be used upsidedown?
    No, Mercotac connectors do have 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 connectors can be mounted at vertical or any angle between vertical and 90 degrees horizontal. This allows for nearly any mounting attitude that would be required. They cannot, however, be mounted with the arrow pointing below horizontal or upside down. (top)

  7. Can a Mercotac® connector be mounted by the upper bushing?
    Yes, in special circumstances. In the case of a vertical mounting (or a mounting somewhat vertical) where the Mercotac connector needs to be mounted below the rotating device, the Mercotac connector 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. (top)

  8. What types of wire connections are needed?
    All the larger Mercotac connectors with tab connections are supplied with push on disconnects. The smaller Coaxial Mercotac connectors use plugs available separately for each model to which customer wires may be soldered. When connecting wires to the stationary floating end of the Mercotac connector allow sufficient length as not to pull on the connector. Do not attempt to solder wires directly to Mercotac terminals.  This will damage interior parts causing the connector to fail, and void the warranty. (top)

  9. Can I solder wires to the Mercotac® connector?
    No. Attempting to solder wires directly to a Mercotac connector will overheat and damage the internal parts, cause connector failure, and void the warranty. Appropriate disconnects are available for Mercotac connectors and always should be used.  (top)

  10. Can standard industrial coax plugs be used on the small Mercotac® Coaxial connectors?
    No. Because the design of the small Coaxial Mercotac connectors is unique, standard industry plugs cannot be used. Accessory plugs are available from Mercotac Inc. (top)

  11. What if I need more than eight conductors?
    The eight conductor Mercotac model is currently the largest connector available. There are two options if more than eight conductors are needed. First, if there is access to both ends of the rotating axis, two Mercotac connectors could be used. This would increase the amount of conductors available to a maximum of sixteen. If this is not a possibility, a Mercotac connector could be combined with a standard slip ring that has a hole in the center. The Mercotac connector would be used for the sensitive signal connections and the slipring for any power connections. (top)

  12. Can Mercotac® connectors be used in damp or corrosive environments?
    It depends on how damp or corrosive the environment is. While Mercotac connectors are constructed of corrosion resistant materials they might not be suitable for all applications depending upon which corrosives they are exposed to. They also are not suitable to be used in “wet” environments without protection. Mercotac connectors are available with a stainless steel ball bearing for use in damp or corrosive environments. We also recommend the use of the accessory “Boot Kit” for additional protection with the larger models. This increases the IP protection rating of the Mercotac to IP51. (top)

  13. Can Mercotac® connectors be used in a vacuum?
    No. Because Mercotac connectors contain liquid substances, a vacuum would tend to cause out gassing and also create internal pressure. This would cause increased rotational torque and possible failure of the connector. (top)

  14. How long can I expect a Mercotac® connector to last?
    All Mercotac connectors are warranted for one full year from delivery.  The life expectancy depends on several application specific factors such as vibration, temperature, RPM, mounting eccentricity, etc. and therefore cannot be accurately predicted for all applications.  However, with no vibration and all other specs being within tolerances, Mercotac connectors typically give years of trouble free service. Under controlled test conditions they typically last for more than a billion revolutions. Of course, Mercotac connectors are entirely maintenance free. (top)

  15. How does movement or vibration in my machine affect the Mercotac® connector?
    Vibration or sudden movement can significantly shorten the life of the Mercotac connector 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 connector. (top)

  16. What is the usual delivery time once an order is placed?
    All standard models of Mercotac connectors are maintained in stock in reasonable quantities at our factory in California, USA. Normal shipping is by UPS Ground, so delivery time is usually one to five business days depending on distance from southern California. Expedited shipping can be arranged. (top)

  17. Do you offer any models with a hole in the center?
    At this time, we do not offer any models with a pass through hole in the center. Mercotac connectors are designed to be compact for mounting at the end of the rotating axis, which makes them less expensive and more durable. (top)

  18. What part rotates?
    In fact, either end can be attached to the rotating device. However, asRotating Connector or Ordinary Slipring?
    described in answer
    No. 5, 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 (also see question No. 7). (top)

  19. Are Mercotac® connectors RoHS compliant?
    No. Mercotac's connectors 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 connectors may still be legally bought and sold in Europe and elsewhere in the world for non-consumer applications. (See our explanation page EU Directives.) (top)

  20. For additional information - click on the following:

    How Does a Slip Ring Work?
    What is a Commutator?
    What manufacturing applications have replaced the traditional slip ring assembly with Mercotac connectors?
    See video clips of Mercotac connectors in action  



Mercotac, Inc.
6195 Corte del Cedro #100 Carlsbad, CA 92011 USA
Telephone: (760) 431-7723  Fax: (760) 431-0905
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