Biomedical Sensors: Types of sensors and How it works

Sensors are everywhere, be it whether we are engineers, doctors or anyone, we are surrounded by sensors. It is a device that converts signals from one energy domain to electrical domain which you commonly see in your homes, offices, shopping malls, hospitals like fire sensors and door sensors which makes our life easier and safer.

Today, I am going to talk about a specific type of sensors: Biomedical Sensors. They are sensors that detect medically relevant parameters which ranges from simple physical parameters like heart rate, galvanic skin response to muscle movements. Through this article, you will learn about:

• Examples and Types of Biomedical Sensors
• How does it work
• Seeed’s Biomedical sensors

Examples of Biomedical Sensors

Today, I will introduce to you 4 types of Biomedical sensors and also Seeed’s Grove Biomedical sensors. Hold up, you may be wondering now, what is Grove?

• Grove is a modular, standardized connector prototyping system.
• It takes a building block approach to assembling electronics. Compared to the jumper or solder based system, it is easier to connect, experiment and build and simplifies the learning system, but not to the point where it becomes dumbed down.
• Some other prototype systems out there takes the level down to building blocks but the Grove system allows you to build real systems.
• You can find out more about Grove here!

Without further ado, let us jump right in to the Types of Biomedical Sensors

EMG Sensor

• Known as Electromyography (EMG), it is a method to evaluate motor unit action potential activity in a muscle region.
• As electrical signals travel through nerves to neuromuscular junctions, the change in electrical potentials (voltage) can be measured.
• Some current examples of the EMG sensors being used today are in VR and prosthetic arms.

Here is our very own EMG sensor!

Grove – EMG Detector

• The Grove – EMG detector is a bridge that connects the human body with electrical through gathering small muscle signals then processing it with 2th amplify and filter. This output signal can be recognized by an Arduino and be added into a 3.3V or 5V control system.
• In standby mode, its output will be 1.5V which will be increased to max 3.3V when an active muscle is detected.
• Some features of our EMG detector are:
  • 6 Disposable Surface Electrodes
  • 1000mm Cable Leads
  • Do not require any additional power supply
  • 3.5mm Connector
• For more information on its hardware and installation, you can click here!

GSR Sensor

• Known as galvanic skin response (GSR), it refers to changes in sweat gland activity that are reflective of the intensity of our emotional state, otherwise known as emotional arousal.
• Skin conductance offers direct insights into autonomous emotional regulation as it is not under conscious control.
• For example, if you are scared, happy, agitated or any emotional related response, we will experience an increase in eccrine sweat gland activity which the sensor can pick up through the electrodes and transmit to the master device.

Here is our very own GSR Sensor!

Grove – GSR Sensor

• The Grove – GSR allows you to spot such strong emotions by simple attaching two electrodes to two fingers on one hand.
• It is an interesting sensor to own as you can create emotion related projects like a sleep quality monitor.
• An example of the use of the GSR sensor currently is lie detectors which the same scientific principle is also applied.
• Some features of the GSR sensor are:
  • Finger straps to with electrodes
  • Able to detect conductance of skin
  • Measures resistance of people
• For more information, installation and examples on using the GSR sensor with the Arduino and Raspberry Pi, you can click here!

Heart Rate Sensors

• Also known as a heart rate monitor, it is a personal monitoring device that allows a user to track and display his/her heart rate in real time or for studies purposes.
• There are two ways (optical and electrical) that this sensor monitors your heart rate which are:
  • Electrical – Consists of 2 elements which are a monitor and a receiver. When a heartbeat is detected a radio signal or coded signal is transmitted, which the receiver uses to display/determine the current heart rate.
  • Optical – Uses a light that shines through a human skin which will then measure the amount of light that reflects back. The light reflections will vary as blood pulses under the skin will go past the light which are then interpreted as heartbeats.

Here at Seeed, we offer 4 different types of Heart Rate Monitors!

Grove – Finger-clip Heart Rate Sensor

• The Grove – Finger-clip Heart Rate Sensor is based on PAH8001EI-2G, a high performance and low power CMOS-process optical sensor with Green LED and DSP integrated serving as a Heart Rate Detection(HRD) sensor.
• This module is based on optical technology which measures the variation human blood movement in the vessel. Low power consumption and flexible power saving mode make it suitable for wearable device.
• Cause the heart rate sensor chip need high processing speed for the algorithm of heart rate data(), this module integrates a STM32, reserved SWD interface allow users to reprogram the STM32.
• Some features of this Sensor are:
  • Ultra-low power consumption – Has power saving mode when there is no movement
  • Flexible Sleep rate control
  • I2C interface
  • Reserved SWD interface
  • Working temperature of -20 to 60℃
  • Sensor area of just 3.0 x 4.7mm
• For more information, installation and examples on using the Heart rate sensor with the Arduino, you can click here!

Grove – Chest Strap Heart Rate Sensor

• This heart rate chest strap kit contains a chest belt and a 5.3 KHz AM receiver module.
• The heart rate measurement kit can be used to monitor the heart rate of patients and athletes, where the result can be displayed on a screen via a serial port and saved for analysis.
• The entire system has lots of advantages, e.g. high sensitivity, low power consumption and portability.
• As the modules communicate with each other via AM, it is very convenient (effective distance is 30cm).
• Some features of the Chest strap heart rate monitor are:
  • Low power consumption
  • Wireless and Convenient to use
  • Built-in ferrite antenna
  • High sensitivity
  • Fully RoHS compliant
• For more information, installation and examples on using the Chest strap heart rate monitor, you can click here!

Grove – Ear-clip Heart Rate Sensor

• The Heart Rate Ear clip kit contains an ear clip and a receiver module.
• It can be used to monitor heart rate of patient and athlete.
• The result can be displayed on a screen via the serial port and can be saved for analysis.
• Some features of the Ear-clip Heart Rate sensor are:
  • Low power consumption
  • Convenient to use
  • High sensitivity
  • Fully RoHS compliant
• For more information, installation and examples on using the Ear-clip Heart Rate Sensor, you can click here!

Grove – Finger-clip Heart Rate Sensor with shell

• Grove – Finger-clip Heart Rate Sensor with shell is based on PAH8001EI-2G, a high performance and low power CMOS-process optical sensor with Green LED and DSP integrated serving as a Heart Rate Detection (HRD) sensor.
• This module is based on optical technology which measures the variation human blood movement in the vessel.
• Low power consumption, flexible power saving mode, shell and two bands make it suitable for wearable device on the finger or wrist easily.

• It has high processing speed for the algorithm of heart rate data with a STM32 and reserved SWD interface which allows users to reprogram the STM32.
• This module equips a shell and two bands that allow users to fix the module on finger, wrist or arm easily.
• Some features of the Finger-clip heart rate sensor are:
  • Low power consumption
  • Flexible sleep rate control
  • I2C interface
  • Area of just 3.0 x 4.7mm
  • Equipped with shell and bands
  • Working Temperature of -20 to 60℃
• For more information, installation and examples on using the Finger-Clip Heart rate monitor, you can click here!

Fingerprint Sensor

• Like optical sensors, capacitive fingerprint scanners generate an image of the ridges and valleys that make up a fingerprint. However, instead of sensing the print using light, the capacitors use electrical current.
• Arrays tiny capacitor circuits collect data about a fingerprint which when connected to conductive plates on the surface of the scanner, can be used to track the details of a fingerprint.
• An op-amp integrator circuit is used to track changes when a finger’s ridge is placed over the conductive plates which will change the charge slightly, while an air gap will leave the charge unchanged.

Here is our very own fingerprint sensor!

Grove – Fingerprint Sensor

• This Finger Print Sensor is an optical fingerprint sensor which makes fingerprint detection and verification super simple.
• It contains a high-powered DSP chip AS601 that does the image rendering, calculation, feature-finding and searching.
• You can register new fingers directly – up to 162 finger prints can be stored in the onboard FLASH memory.
• There’s a red LED in the lens which will light up during identification so that you know its working condition.
• It is easy to use and by far the best fingerprint sensor you can get.
• Some features of this Grove-Fingerprint Sensor are:
  • Storage capacity of up to 162 fingerprints
  • Working Temperature of -20 ℃ to 50 ℃
  • Supply voltage: 3.6~6.0 V
  • Operating current(Max) : 120 mA
  • Security level 3 with False acceptance and false reject rate at 0.001% and 1.0% respectively.
• For more information, installation and examples on using the Finger-Clip Heart rate monitor, you can click here!

Summary

Through this article, you have learnt about 4 types of Biomedical sensors and monitors which you can implement in your future projects. Do you need inspiration for project ideas? You can take a look at some of our Heart Rate sensor project ideas using the Grove Sensors here!

Do not own a biomedical sensor yet? What are you waiting for? You can get one here now!

About Author