Sensor Mind: Essential Questions to Ask Before Choosing Sensors for Your Design

You will need sensors to complete your new appliance, building automation product or automated production system. You may need customization for a specific touch mount. While price and delivery are critical decision factors, other considerations determine the successful selection of a sensor.

Here are some basic facts about yours selection of sensors and four important questions whose answers must carry considerable weight in the decision-making process.

Magnetic sensors for proximity detection, positioning and control

Ridge switches have two ferromagnetic blades (reeds), hermetically sealed in a tubular glass shell. The contacts of each reed have a thin layer of precious metal to provide an electrical connection with low resistance. The glass shell is filled with nitrogen gas to eliminate oxygen and prevent contact oxidation. Reed switches are activated by either a permanent magnet or an electromagnet. The relative hardness of the reed blades, the small gap and the overlap between the two contacts determine the sensitivity of the switch, determined by the intensity of the magnetic field needed to change the state of the contacts. Unlike an integrated circuit sensor, the reed switch does not require a power supply to operate. Thus, the reed switch is an excellent control element in battery-powered products.

Hall effect sensors generates voltage when exposed to magnetic field intensity and when powered by a current source. The sensor is a semiconductor-based material. Hall voltages are microvolt and millivolt levels; thus, the Hall effect sensor requires signal conditioning. In addition, the semiconductor element requires temperature compensation and EMC / ESD protection. Hall-effect sensors monitor proximity and provide continuous rotational or linear positioning.

Reed relays combine reed switch and control winding. As with other relays, this provides galvanic isolation between the coil control circuit and the controlled load. The small size of the relay and the high magnetic efficiency allow lower coil drive power compared to other types of relays. Other advantages include high insulation resistance, low contact resistance and long contact life.

TMR switches integrate Tunneling Magneto Resistance (TMR) and CMOS technology to provide a high-sensitivity, ultra-low power magnetic switch. It features a TMR magnetic sensor and CMOS signal processing circuit in the same package, including a built-in TMR voltage generator for precise magnetic reading, a TMR voltage amplifier and a comparator plus a Schmitt trigger to provide noise-canceling switching hysteresis. An internal belt regulator provides temperature-compensated supply voltage for internal circuits, allowing a wide range of supply voltages.

Temperature sensors

Thermistors are thermally sensitive resistors whose resistance is a function of their temperature. Negative temperature coefficient (NTC) thermistors decrease their resistance when the temperature rises, and positive temperature coefficient (PTC) thermistors increase their resistance when the temperature rises. Thermistors provide high accuracy in a narrow range of approximately -50 ° C to 100 ° C. Thermistors have many predictable characteristics and excellent long-term stability; they are ideal sensors for temperature measurement and control applications.

Platinum resistant temperature detectors (Pt-RTD) have an almost linear change in resistance with all temperature changes. Platinum RTDs maintain a significant and uniform resistance change rate over a much wider operating temperature range than the thermistor. Platinum RTDs are excellent for measuring and control applications with temperatures ranging from -70 ° C to 500 ° C.

4 questions to ask before choosing sensors

1. Does the supplier offer a wide range of sensors and other components?

Consider a manufacturer that manufactures several types of sensors. Such a manufacturer has experience in a wide range of technologies and is more likely to be able to meet custom requirements.

In addition, a manufacturer with an extensive product line can meet many of your other component requirements. This allows you to reduce the number of suppliers and simplify your supply chain.

The knowledge and experience of the manufacturer with an extensive portfolio can turn into innovation in new products. Their innovations can give your products a decisive competitive advantage in the market.

2. Does the provider offer application assistance?

Implementation assistance from technical staff can save valuable development time and help select the right sensor model. They can ensure that you keep in mind all parameters related to the use of the sensor, such as temperature effects, vibration and sensitivity to electrical noise.

3. Does the supplier provide custom engineering?

Do you have critical size or shape requirements for your sensor? You may need a little more sensitivity or a specific type of electrical connector. You will want your provider to have customized engineering capabilities to meet unique needs. Many suppliers sell only their standard products and this lack of service should hamper any expectations for a long-term relationship with the supplier.

4. Does the supplier have the capacity to manage your order requirements?

You do not want to lose revenue due to unreasonably long delivery times for sensors and other components. Make sure that your supplier can meet your estimated order requirements and respond adequately to unexpected large orders.

Advantages of choosing a good sensor supplier

Although the provider may meet the basic requirements discussed here, the price for their sensor may not be the lowest available. However, you benefit from savings on development time, reduced warranty costs, higher reliability and greater customer satisfaction in the long run. Choosing a provider should be as important as choosing your sensors.

Additional questions about sensors

Download the White Paper, Eight considerations when buying sensorsto learn about other issues you need to keep in mind before choosing your sensors and the company that makes them. See also Guide to selecting sensor products for more information on choosing the best sensors for your application, courtesy of Littelfuse, Inc.