Shimmer GSR Calibration






Shimmer is a wireless sensor platform developed by Shimmer Research that can be used either as a data logger of biosignals to be stored in an SD card or to capture different physiological data in real time. Currently Shimmer provide modules that can sense motion through Gyroscopes and Accelerometers, vital signs and bio signal (ECG, EMG, GSR and Strain Gauge) and ambient sensing (PIR, GPS and Temperature). The modules can send data in real time either through Bluetooth or through an 802.15.4 Radio. Shimmer modules are based on opensource software making it easy to develop applications and firmware for the Shimmer modules. You can find more information about Shimmer Research and its products here . During my employment at Lancaster University as Research Associate, I worked with the Shimmer GSR 2R version. The latest sensor version is Shimmer 3 and it is relatively smaller than Shimmer 2.

In general the manual instructions of how to pair the ShimmerGSR module to the laptop are pretty clear and it is similar to pairing any other bluetooth device to a laptop. In the version of the manual I had, the installation instructions are in pages 1-22.

One detail that is not mentioned in the manual and it is important is that when you use the ShimmerConnect software from the USBLive, you can choose from the Menu between 4 different resistors for the GSR (10k-56k, 56k-220k, 220k-680k,680k-4.7m) which to my understanding correspond to different skin resistance thus different skin types. Unfortunately only one of the will give you the data that you want but before testing it with subject you need to calibrate it and find which if the sensor corresponds to the user’s skin type. So you need to test all 4 of them starting from selecting the 10k-56k resistor and moving to the next resistor after each test. The 1st photo below shows a wrong selection of resistor;

GSRShimmerConnect
Notice that the GSRResistance box is higher than the upper limit of the selected Resistor. If you see in the GSR resistance box ” > max ” or ” < min " that means that you have selected the wrong resistor and you should try the next one from the list. The photo below shows the correct selection of resistor.

GSRShimmerConnect2

Notice that the GSRResistance box actually shows numbers transmitted by the ShimmerGSR. Which is exactly what you want. A wrong selection of GSR resistor will give you a more or less flat line of data since the skin resistance recorded is below or above the selected resistor measurement band.

Good luck!

If you found what you read helpful or inspiring, the least you can do out of academic or research courtesy is to mention my website or my name when using pieces of information from here.

Thank you!

Categories: Projects