Frequently Asked Speed Sensor Questions


What is a motion sensor?

This generally refers to sensors using infrared, microwave or optical technology that are used, for example, in the security industry to detect movement over fairly large areas. Our company does not make these types of sensors. What we manufacture are speed sensors, also known as pickups, magnetic pickups and speed transducers, that sense the motion of a rotating object such as a gear, shaft, turbine, etc. The “motion” in our name is angular motion, not lateral movement. Through the use of interruptions in magnetic fields, speed sensors create output each time a metal object passes by the tip of the sensor. The number of these occurrences can be converted into how fast the gear, shaft, etc. is turning.

Are MSI sensors RoHS compliant?

The scope of the Directive 2002/96/EC (WEEE) plays a role in determining what electronic devices must comply with the RoHS Directive 2002/95/EC. Pursuant to Annex IA, MSI product falls under Category 9 (Monitoring and Control Instruments), which is currently exempt from RoHS compliance under Article 2 of the Directive 2002/95/EC.

Certain of our sensors designed for use in high temperature, hazardous locations necessitate the use of leaded, high melting point solder. Directive 2002/95/EC permits the use of high temperature leaded solders.

Although it is not currently a requirement per the WEEE directive, Motion Sensors has determined proper steps to bring our sensors into compliance with the RoHS directive. If you determine that RoHS compliance is necessary to meet your requirements, please contact us directly to discuss in detail.

Do you make products for hazardous locations?

Yes. Motion Sensors makes sensors and preamplifiers that are certified in both North America and Europe to the most stringent requirements for intrinsic safety. We also make explosion proof versions of sensors with NPT threads and pigtail leads at the connector end for explosion proof applications.

Are your products ATEX certified?

Yes. Motion Sensors is certified to the ATEX standard (compliant to 2014/34/EU).

Are your products CE compliant?

Standard VR and RF sensors are passive devices and as such do not require a CE marking. Much like a resistor or a capacitor, the sensor is seen as a component and does not require any CE certification until it is put into a system. Motion Sensors does, however, manufacture and sell products containing electronic components, as well as stand-alone analog and preamplifier boards for which we have obtained CE certification. Our Digi-Pulse series of VR and RF sensors, Hall Effect sensors, Magnetoresistive sensors, and Preamplifier Boards are all CE compliant to EMC Directive 89/336/EEC.

I only need a few sensors. Do you sell sensors in small quantities?

Yes, however, quantity discounts apply when purchasing in larger quantities.

What is the maximum transmission distance of the Digi-Pulse series of sensors?

The Digi-Pulse series of sensors are suitable for long transmission distances; however the maximum useable distance is a function of the capacitance, inductance, and resistance of the type of cable used. With communication cables such as UTP #24AWG the outputs of the Digi-Pulse sensor family can be extended up to 100 meters.

My particular application calls for a sensor size different from the products specified on this site. Can you make a sensor based on my specifications?

We welcome inquiries for custom designs. A large percentage of our business is making custom products and/or modifying our existing products to specifically satisfy customer requirements. We pride ourselves on being customer oriented and responsive to customers’ needs. We have developed a reputation for providing innovative custom products with a fast response time and reasonable cost.

What is drag? Why should I worry about it?

Drag is the influence of a speed sensor’s internal magnet on the target. Usually drag does not affect target devices like gears, shafts, or rotors that are being driven. However, in applications like turbine flowmetering where the turbine blades are free spinning and turn based on the pressure and flow of the fluid or gas flowing through the meter, drag could retard or hinder its ability to turn freely. This is especially true in small diameter meters and low flow applications. Motion Sensors makes specially designed low drag versions of our variable reluctance (VR) speed sensors. If drag is of great concern, we also offer modulated carrier (RF) sensors which have absolutely no drag and are ideally suited for low flow applications or where maximum turndown ratios are desired.

Do you make a sensor that eliminates electrical interference that may cause erratic readings?

MSI uses a number of different techniques to combat this problem. With reference to VR speed sensors, our Humbucking sensors, when used with differential amplifiers, offer extremely high resistance to electrical noise and interference. These sensors utilize dual coils to eliminate or reduce electrical interference and noise generated by electric pumps, motors and overhead lines. In the case of our Digi-Pulse sensors, interference and noise is reduced by placing the electronics and transducer close together in the same housing, thereby substantially reducing the opportunity for noise to come between them. On all our electronic circuits, Motion Sensors also uses “filtering” techniques to cancel out and eliminate noise and other interference.

Does the device I am trying to sense have to be made of ferrous metal in order to sense it?

No. Modulated carrier (RF) sensors are capable of sensing certain non-ferrous metals like aluminum and non-magnetic stainless steel. We also make inductive VR sensors that can sense moving magnetic fields such as center pole magnets or magnets embedded in the outer rim of the rotating device to give the sensor a field to sense.

Will your preamplifiers operate with sensors other than those manufactured Motion Sensors?

Yes and No. Our preamplifiers will work effectively with other VR speed sensors; however, the modulated carrier preamplifiers are designed to work best when coupled with our RF sensors. RF sensors from other companies need to be tested to verify compatibility. We can also modify our preamplifiers to work with almost any RF sensor.

What is gauss strength?

Gauss strength is simply the strength of the magnet in a magnetic speed sensor. Gauss strength can be adjusted to increase signal strength, reduce drag, etc.

What is a focusing tip?

The “focusing tip” is a term used to describe the constriction of the magnetic field to produce a longer, narrower sensing field at the front (sensing end) of the sensor, thereby allowing greater air gap, sensing distance and increased signal strength. To our knowledge, Motion Sensors is the only manufacturer that uses this technique on a production basis – in our Premium series of VR speed sensors.

How important is hermetic sealing?

When an application occurs in a more severe temperature environment, due to temperature extremes, thermocycling, or high levels of moisture or humidity, sensors sealed by epoxy encapsulation break down and develop crazing cracks that permit moisture to penetrate, from condensation immersion or humidity. This moisture eventually corrodes the sensor’s internals or shorts out the circuit, causing failure. Hermetically sealed sensors, by definition, are 100% water and airtight and maintain the integrity of the sensor’s internals. These sensors are the sensors of choice whenever severe environmental conditions are present.