IR Sensors

An IR sensor, or infrared sensor, is a sensor that uses infrared light. IR sensors detect the heat (infrared radiation) emitted by people and objects for enabling operation of various devices. This section presents the features and application examples of IR sensors that make our daily lives more convenient.

What Is an IR Sensor?
IR Sensors Using MEMS
Application Examples of IR Sensors
MinebeaMitsumi’s IR Sensors

What Is an IR Sensor?

IR sensors are sensors that receive infrared light and convert it into electrical signals. There are two types of IR sensors, each using a different operating principle: thermal sensors that detect the electrical properties changed by infrared heat, and quantum sensors that detect electrical phenomena caused by light energy.

Thermal IR sensors

Thermal IR sensors have a wide wavelength range and can be used at room temperature, so they do not require a cooling device, which enables a compact, lightweight design for products in which they are mounted.

Quantum IR sensors

Quantum IR sensors have high detection sensitivity and excellent response speed. However, a cooling device is required to take advantage of their high sensitivity.

Infrared light has longer wavelengths than light visible to the human eye, and is classified into three categories according to its wavelength: near infrared light, mid infrared light, and far infrared light.

Near infrared light, with wavelengths of approximately 0.7 to 2.5 μm, has wavelengths near red visible light and is used in infrared cameras, surveillance cameras, remote controls, and biometric authentication (vein authentication). Mid infrared light, also called middle infrared light, has a wavelength of approximately 2.5 to 4 μm and has the characteristics of both near infrared light and far infrared light, and when we simply refer to “infrared light,” we are referring to those with this wavelength. Major applications include spectroscopic analysis of organic chemicals and other substances. Finally, far infrared light is infrared light with wavelengths of approximately 4 to 1,000 μm. It is used in heating equipment because it is the most effective in warming objects, and is also used in applications such as thermography and nighttime photography systems.

IR Sensors Using MEMS

IR sensors using MEMS can be made ultra-compact and are easy to mass-produce. Major applications include so-called white goods such as refrigerators and air conditioners, temperature monitoring equipment, and systems for monitoring abnormal temperatures.

Inexpensive thermistors are widely used as sensors that sense temperature. However, today, IR sensors using MEMS are replacing thermistors in a variety of devices because they are more responsive than thermistors and can detect using both contact and non-contact methods. In particular, MEMS can be miniaturized and easily mass-produced, so they are often used in white goods for the purpose of adding value in terms of safety and convenience.

Application Examples of IR Sensors

IR sensors are being used all around us in our everyday lives. For example, in air conditioners, they detect heat emitted from people in the room, and in refrigerators, they detect uneven temperature of food in the cabinet for enabling efficient cooling. Recently, these sensors are being incorporated into non-contact thermometers, which can instantly measure a person’s body temperature by pressing a button near the person being measured. They are also used in abnormal temperature monitoring systems.

MinebeaMitsumi’s IR sensor is a thermopile sensor using MEMS technology. To perform non-contact measurement of the surface temperature of an object, this sensor uses the principle that a thermoelectromotive force is obtained that is proportional to the incident energy (heat) of the infrared radiation emitted by the object. The output is converted to a digital value inside the sensor and is output.

Features

MinebeaMitsumi’s IR sensors have a noise equivalent temperature difference (NETD) of 0.06°C or less, which is one of the lowest in the industry, for enabling viewing of fine temperature differences. Furthermore, since the temperature value is directly output, it is easy to import into software applications. Also, the IR sensor has an integrated connector unit, eliminating the need for a separate dedicated sensor board and allowing a wider degree of freedom in installation.

Product Descriptions

	MMS701

Supply voltage range (VDC)	4.5 to 5.5 (5.0 typ.)
Object temperature range (°C)	−40 to 80
Operating temperature range (°C)	−40 to 80
Viewing angle (°)	25
Number of pixels	1 (1 pixel)
Temperature resolution (NETD) (°C)	0.06
Temperature accuracy (°C)	±1.5 max. at adjustment point
Power consumption (mA)	3.5 typ.
Interface (output format)	I2C
Dimensions (mm)	11.6 × 12.0 × 8.7*

Including rear connectors
Adjustment points: (1) Tx = 5°C, Ta = 5°C (2) Tx = 25°C, Ta = 5°C (3) Tx = 25°C, Ta = 5°C Tx: Object temperature, Ta: Reference temperature

Usage Example

As with typical IR sensors, MinebeaMitsumi products are anticipated to be used in a wide variety of home appliances. In addition to refrigerators and air conditioners, they can be used to detect the surface temperature of clothes in clothes dryers to prevent uneven drying, and in facial care devices to detect skin temperature.