Are SpikerBoxes calibrated in volts?

Unfortunately, the SpikerBox is not calibrated in volts. AD units of SpikerBox are linearly proportional to volts.

Units can be expressed as C*V (volts multiplied by constant) where C is an unknown constant that should be determined by calibration of the device and V are volts. RMS has the same units as the signal.

Even though you do not know the actual value of constant C the measurements are very useful for expressing relative quantities like the percentage of increase of signal activity and similar (since constant C will disappear from the equation when you divide two RMS values).

The main issue is that in order to make calibrated gear, the whole process must be more expensive. We made a trade-off so that we make accessible (not expensive) devices that can be in more people’s hands. With these devices, you can still conduct a lot of real experiments and learn a lot. Only experiments that require absolute measurements of voltage can not be done properly.

Now that we are moving all of our devices to USB… we can finally calibrate SpikeRecorder. Traditionally, we used the analog in (mic) port for recordings which meant we did not know what the volume was set to on the SpikerBox, or how the different phones attenuated the signals. But thanks to our begrudgingly slow move to USB… we can now capture the signals at the source and tell SpikerRecorder what the voltage was of your signal. (Note that spikes are measured in low milliVolts (mV) or 100s of microVolts (uV).