What “5 million cycles” really means.

The short answer

A life rating such as “5 million cycles” is the number of operating cycles the potentiometer survives in a defined test while its resistance stays within an agreed limit. It is a comparison figure measured under test conditions, not a promise for every installation. To use it, estimate how many cycles your product will see, add a safety margin, and check the conditions that shorten life in practice.

How rotational life is defined

• Cycle: normally one movement across the travel and back. Confirm the exact definition in the datasheet, because it changes the number.
• No-load: the test is run without external mechanical load on the shaft or lever.
• Acceptance limit: the allowed change in resistance at the end of the test. For example, Cooka’s SRS22 allows a total resistance change of no more than ±5%; the SVR01 slide potentiometer allows ±20%.

Two parts with the same cycle count but different acceptance limits are not equivalent; compare both numbers.

Estimate the life you need

Multiply how often the control moves by how long the product must last, then add a margin.

Example: a machine joystick moved 500 times a day, 250 working days a year, for 10 years needs 500 × 250 × 10 = 1.25 million cycles. With a margin for heavier users, a 2 million-cycle or 5 million-cycle part is the safer choice.

Automated parts move far more than hand controls: a motorized fader following automation or a feedback sensor on an actuator can accumulate cycles every second, so count system movements as well as human ones.

What shortens life in practice

• Dither: small, constant oscillations around one position (common on servo feedback) wear a single spot of the track much faster than full sweeps.
• Side load and misalignment: force on the shaft or lever loads the bearing and wiper unevenly.
• Electrical load: drawing current through the wiper accelerates wear; use the potentiometer as a voltage divider into a high-impedance input.
• Contamination and moisture: dust, oil and condensation reach the track unless the housing is sealed for the environment.
• Temperature: operation near or beyond the rated range ages the element and lubricants.

Cooka life ratings by series

Values from the published series pages. Confirm the life code and test definition for the quoted configuration.

How to specify life when you enquire

1. Your estimated cycles over the product life, and how you calculated them.
2. Whether movement is full sweeps or small oscillations.
3. Mechanical load on the shaft or lever.
4. Electrical load on the wiper.
5. Temperature, sealing and contamination.