Technical FAQs

Our engineers, customer service reps, and machinery analysts are available to answer your questions.

What's the difference between capacitive discharge ignition and inductive ignition systems?

Inductive ignition systems have a longer, variable spark duration. Inductive ignition systems are better suited for lean burn engines.

When selecting a pickup, how do I determine diametral pitch?

Divide the number of teeth on the gear by the diameter of the gear in inches.

How can I maximize the output voltage of a passive magnetic pickup?

If you know that your particular gear and pickup will not provide an adequate input signal to operate a meter or a speed switch at the slowest speed of interest, you can:

  • Accept a higher minimum speed
  • Use a different gear (one with fewer teeth or a larger diameter)
  • Use an externally-powered device instead of a signal-powered unit
  • Change to a different passive pickup that provides better output for your application

Does gear tooth size matter when choosing a magnetic pickup?

Yes. For maximum output and a sinusoidal waveform:

  1. The dimension of the tooth top surface should be equal to or greater than the pole piece diameter.
  2. Tooth height should be equal to or greater than the space between the teeth.
  3. The space between teeth should be approximately 3 times pole piece diameter.
  4. The air gap pole piece clearance (should be as small as possible 0.005" typically).

What is gate time?

For a digital meter to accurately display an RPM, it must count the input pulses from a pickup (speed sensor) or other frequency source - over a specific time span. That time span is known as gate time. In a sense, the meter's circuitry opens an electronic gate for the incoming pulses, counts these pulses, and then - when the calibrated gate time runs out - closes the gate. Circuitry then calculates the RPM and sends the equivalent RPM value to the LCD or LED. The process is repeated as frequently as the gate time value.

How do I calculate gate time?

Gate time can be calculated by two methods:

  • Gate Time = 60 ÷ (number of teeth or gear discontinuities)
  • Gate Time = (maximum RPM) ÷ (equivalent frequency in Hz at that RPM)

What is a powered pickup?

Powered Pickups are DC powered, providing a constant amplitude output—roughly equal to the DC input—independent of gear or shaft speed. They still must sense a ferrous material, but can perform at zero or near zero speed, providing a usable signal when a passive pickup can’t. NOTE: As a result of the power input, they cannot be classified as intrinsically safe.

What's the difference between intrinsically-safe and explosion-proof?

Intrinsically-safe products mean that regardless of a circuit's condition, power levels will not be of sufficient magnitude to ignite a specific hazardous mixture.

Explosion-proof products are surrounded by an enclosure that can withstand the pressure of a mixture exploding inside the enclosure and prevents propagation of the explosion to the surrounding atmosphere.

What is a pole piece?

The pole piece is a part of a speed sensor. It IS a cylindrical permanent magnet behind a soft iron rod (the actual pole piece) wound with fine magnet wire.

The pole piece may protrude from the pickup body, or it may be "blind end," where the tip of the pickup is behind a solid housing front because the pickup body is one piece.