Mueller Electric has taken efforts to not include materials in its products known to the state of California to cause cancer. The bulk of Mueller’s products are compliant (Most Clips and Insulators) to being below the limits for these material limits and will not be marked as being compliant. However testing and costs prohibit us from testing and verifying each and every product. In those cases Mueller will affix the following label to each shipping package for each item once shipped.

Bare alligator clips are not rated for voltage because they do not have any insulation on them. Mueller makes insulators for most of its clips, but the insulators are not designed to protect a user working on a live circuit. Most of the insulators Mueller sells are designed to prevent the clips from touching other conductive items only. The dielectric breakdown voltage thru Mueller’s insulators is at least 3kV, but the jaws of most clips are still completely exposed and potentially dangerous. Because of this, Mueller does not recommend connecting or disconnecting its clips to live circuits with potentials higher than 42 Volts. If the clips are used in a hands free testing environment, then the clips with installed insulators can be used safely up to 3kV. A hands free testing environment means that the clips are attached or unattached only when the circuit is not energized.

The reason why Mueller’s insulators do not meet the requirements for human protection at elevated voltages are as follows:

  1. To meet the IEC61010-031 requirements, insulators would need to be permanently installed (They cannot be slipped on or off or just moved out of the way)
  2. There must be a guard placed at a specified distance to prevent accidental contact with exposed metal parts
  3. A finger probe applied at any angle is not allowed to touch any current carrying exposed metal
  4. Clearance and creepage distances would need to be maintained.

In most cases, clips/insulators that meet these requirements would be too cumbersome and too expensive for general testing needs.

Mueller Insulators and Mueller Test leads use the same color chart as resistors.
-0 Black
-1 Brown
-2 Red
-4 Yellow
-5 Green
-6 Blue
-8 Gray
-9 White

Note: All colors may not be available for all products.

The number of requests for Crane circuit board connectors has diminished over the years. Most connector series are still available, but they may have limitations of pin lengths or plating options. There are a few series that have been inactivated due to the cost to maintain sufficient component inventory levels.

Mueller is a high volume manufacturing company that uses distributors to sell its standard products. The business model does not have the order entry or shipping staff to process the thousands of orders that are placed every day. If a distributor does not have inventory of the part you are interested in, then place the order with them anyway. As long as Mueller has the part in stock, there will only be a couple days delay in receiving your product through the distributor. Mueller will sell direct to OEM’s as long as they meet the minimum order requirements. Please contact customer service for details.

Mueller offers a limited number of test leads, clips and accessories that are UL Listed. For a complete list please follow the following link: Mueller UL Products

A Kelvin or Kelvinized clip has jaws, teeth or contacts that are electrically isolated from each other. In practice one jaw will carry the current and the other jaw will be used to sense the voltage. When used properly, Kelvin clips provide a much more accurate reading at low voltages compared to a single wire clip.

There are two main differences between PVC and silicon jacketed wires. Although the electrical insulation is approximately the same, silicon jacketed wires are more flexible and can withstand much more heat than PVC jacketed wires can. Silicon jacketed wires cost much more than PVC jacketed wires.

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