Frequently Asked Questions
- Simsense has a multichannel PPG. What are the wavelengths of each PPG LED?
- PPG wavelength as per the LED data sheet:
LED color Wavelength(nm) Blue 460-470 Green 520-535 Yellow 585-594 Red 644-676 IR 850-970
- How do I activate the ECG?
- Simband has a passive ECG sensor. It does not have an active mode. While wearing Simband, one ECG electrode touches your radius while the other electode is in the clasp (as shown in the picture below). In Monitor mode, touching the clasp with your other hand closes the loop around your heart, activates the sensor and starts recording ECG data.
- I have noticed that Simband sometimes vibrates. What do these vibrations mean?
- When Simband is turned ON, the first vibration indicates that the system is ready to function.
- Simband vibrates when any settings flag has changed or any configuration is changed/updated, reflecting that the system is ready after soft reset.
- Simband vibrates when there is a software update available, along with a pop-up notification.
- Simband vibrates when the battery is 'low' and 'extremely low', and while shutting down.
- What is the PPG LED drive current?
- The Simsense PPG should be calibrated for every user before capturing PPG data. The PPG LED drive current for each PPG channel will be displayed after the calibration process is finished.
- What do the different Simband charger blinking patterns represent?
- Refer to the diagram below:
- How many PPG channels are available on Simband? Which wavelengths are associated with each channel?
- Simband has 6 LEDs and 5 photodiodes, which enables Simband to generate 30 PPG channels. Simband currently exposes 8 channels through its APIs, which cover all the wavelengths from different PPG locations. We think these channels provide the best-quality signals.
Channel name LED color Wavelength(nm) 0/A Blue 460-470 1/B Green 520-535 2/C Red 644-676 3/D IR 850-970 4/E Green 520-535 5/F Green 520-535 6/G Yellow 585-594 7/H Green 520-535
- I am looking for TIA gain, ADC characteristics, bits, reference voltage, etc. for the PPG circuit. Where I can find that information?
- Great question. We have disclosed all the necessary parameters of each sensor circuit available in Simband here. If something you're looking for is missing, raise your hand… I mean, email us :)
- What is the sampling rate of the data generated by Simsense?
- All the data generated from the different sensors of Simsense is re-sampled at 128 Hz, time-stamped and time-synchronized.
- Why is 128 Hz used as a sampling frequency for the PPG signals?
- We think 128 Hz is a balanced choice between sample resolution and power consumption. Also, 128 Hz sampling provides sufficient resolution to perform time-centric tasks like Pulse Arrival Time calculations—as fast as 200 ms (typically 180-400 ms). 128 Hz sampling means 7.8 ms per sample, which is less than +/- 4% jitter in PAT calculation. Some sensors acquire data at different rates and some are asynchronous to others. To make the math and life easier for algorithm developers, we synchronize all sensors using a sample rate convertor to 128 Hz.
- Simband has accelerometer in Simsense and in the base / watch unit. What are its axial orientation?
- Both accelerometer have different axial orientation. Refer to the diagram below:
Simsense accelerometer orientation
Base / watch accelerometer orientation
- Can I develop apps on Simband?
- Simband runs Tizen, and you can develop apps according to Tizen's standards. Our project focuses on building new, innovative algorithms, using the data that comes out of the sensor. Developers are invited to write algorithms in C and C++ running on top of our Simband runtime that read, compute and save data in our streams. These C/C++ Simband algorithms will run natively in the Tizen application. Learn about writing algorithms.
- Great, how can I start? Do you have an SDK?
- Very soon; it is already a work in progress. But we call it an ADK (Algorithm Development Kit) instead of SDK, since you can only develop algorithms on Simband.
- Can an algorithm developer get direct access to real-time data?
- Yes. You can access all the data from ARTIK Cloud. We are also working on an even cooler developer tool. Stay tuned.
- Can I use the SD card for storage and easier transfer of data?
- We don't support SD cards, but the Simband prototype comes with a charger with a USB port. You can connect the USB port to your computer but you cannot expect to extract/transfer the data or any files.
- I heard Simband was open source. Where is the source code?
- You are right, we plan to make Simband open source. The source code is not available, yet, but if you feel brave you can request access.
- Who is behind Simband?
- Simband is the result of the work of a small, very energetic team. Here we are two weeks before our November 2014 launch.