Sensors explored: Galvanic skin response

Wearables are getting smarter and that's a good thing. It can be a bit of a minefield keeping track of all of the tech being crammed into fitness trackers, smartwatches and VR headsets, though. It's also not always clear exactly what that new tech does or how it's going to help you measure, track and analyse.

That's why we wanted to start honing in on the sensors and features that make our wearables tick. We're starting things off by taking a closer look at a sensor that's starting to creep its way into more devices.

Read this: What wearables will measure in the future

Galvanic skin response sensors have appeared in both versions of the Microsoft Band, the Jawbone UP3 and the recently recalled Intel Basis Peak. It's also set to feature inside Vinaya's upcoming Zenta biometric bracelet and the emotion sensing Feel wristband.

So why is GSR a big deal? We explore how it works and what it's going to bring to the wearable tech party.

Origins of GSR

Before we get on to what a galvanic skin response sensor actually does, we're going take a look back at how it came to prominence and why you might actually be more familiar with it than you think.

The ability to measure galvanic skin changes, also known as electrodermal activity, goes way back to the 1800s, but in modern day terms it's probably best known for being the tech you find inside a 'lie detector' test.

As we covered in our origins of the fitness tracker, it's was cropping up in lie detector machines to carry out polygraph tests before World War II. Used along with sensors to measure pulse rate and blood pressure, it's helped sniff out the telltale physiological indicators of fibbing to the police.

How it works

So here's the technical bit. Understanding exactly what happens when the sensors are called into action. Essentially, GSR sensors are able to measure the electrical conductivity of the skin using electrodes. This electrical conductivity is tied to changes in moisture levels in the skin when the sweat glands are more active. When you sweat more, the electrical conductance in the skin changes.

Sweat glands are tied to our nervous system and body processes like our immune system, so GSR can help tap into information about our current physiological and psychological state. That's why it's considered a good fit for both fitness trackers and stress combating wearables for instance.

Those sweat glands can be found all over the body, but there's a whole lot of them situated around the hands and the feet. That's why makes sense that companies making wrist-worn wearables are playing around with GSR sensors on that particular part of the body.

What GSR tells you now

Galvanic skin response sensors, whether it's working alone or alongside other sensors, can tell us a little or whole a lot. Take the Microsoft Band for example. It includes a GSR sensor to distinguish whether the wearable is being worn. But combined with the other sensors included (heart rate and skin temperature), there's potential here for the ability to measure stress and feed that information back to the wearer to aid recovery or inform when they're putting too much strain on their body.

Jawbone's UP3 tracker uses a series of bioimpedance sensors which measures the resistance of body tissue to tiny electric current. These sensors include heart rate, respiration rate and galvanic skin response. These collectively aim to give an indication of your physiological state. Currently this family of sensors focuses on delivering reliable heart rate information, but it could open the door for monitoring stress and fatigue.

What GSR could tell you one day

Something that's noticeably missing from wearables right now is the ability to reliably monitor emotions and that's where galvanic skin response sensors could really play a big part.

Essential reading: Emotion sensing wearables are on the rise

When our emotions are aroused, our body reacts. The heart beats faster, breathing can become heavier and you start to sweat more. That signals a change in the electrical conductivity of the skin and that's where GSR could come into action.

Zenta, an emotion sensing wearable, is tapping into galvanic skin response and along with a host of other biometric sensors hopes to identify and measure how happy, angry, stressed or relaxed we are. The Feel wristband similarly wants to stop you feeling stressed out and uses multiple sensors including GSR to deliver data to your phone. The idea is to help you identify what is making you feel happy, sad or even a little angry.

Galvanic skin response has the potential to play a major role in the future of medical grade wearables, helping to track emotional reactions to patients that suffer from phobias or even post-traumatic stress syndrome. Dealing with stress and anxiety is already big business. What's clear is that GSR sensors inside wearables is a trend that's only going to grow and grow.