Impedance and Offset in Designs (BioExplorer)

To test impedance or offset, download a design:

EEG + Impedance or Offset

EEG & HEG + Impedance


How to test

For Impedance, in Wiz window select Settings | Mode | 4 Channel and Helper | Impedance Check
Under 20 kOhm is good; up to 50 kOhm is serviceable

For Offset, in Wiz window select Settings | Mode | EEG+Offset
Wiz can tolerate offset voltages +-250mV

Notes from Bruce on the Wiz

BioExplorer does not know which device is connected (although I am currently talking to Larry at BioExplorer about whether maybe it needs to)

BioExplorer only knows Modes.

Modes are consistent across Models, so Mode 1 in the U-wiz is the same as Mode 1 in the E-wiz is the same as Mode 1 in the Q-wiz.

Modes describe
– number of channels,
– sampling rate and
– bandwidth.

A Mode is akin to “Profiles” in the Pendant. Overlaying this Mode is a separate control that can switch the _Modality_ from EEG to HEG. The _Mode_ info does not change. Now in the Q-wiz this is dynamic, plug in a headband and a channel(s) will change from EEG modality to HEG modality automatically, and BioExplorer gets to know automatically. In the other products, U/X/E/H, they are either EEG or HEG only device and the _Modality_ is fixed. EG, H-wiz cannot send EEG modality, but it can send Modes 0/1/2/3.


Mode 0 (no blinks “Prog”) – program Mode (device is listening not transmitting) – used for upgrading firmware from time to time.
Mode 1 (one blink “HEG”) – 32sps, 10Hz (useful for HEG and and maybe SCP, ECG only), slow sampling better for tablets
Mode 2 (two blinks “EEG”) – 128sps, 45Hz (standard EEG)
Mode 3 (three blinks “ExG”) – 512sps, 200Hz (EMG (high bandwidth), ECG & SCP (accepts larger signal), but can also be used with EEG at slightly reduced sensitivity
Mode 4 (four blinks “4ch”) – Q-wiz only, 4ch 256sps/45Hz

I will talk about Mode 4a and 4b later.

For each of these Modes 1-4, there is a function that stops the transmission of the EEG signal, and substitutes EIM (electrode impedance measurement) info on that channel. EIM is in HEG format (modality is you will) so this allows the EIM meter to be connected to BioExplorer source object configured as HEG, and the meter only becomes active when the function is invoked. This allows the EIM designs to be well behaved. Not so for offset potential which when this function is invoked, stops the EEG and substitutes the electrode offset potential (EOP), however this is encoded as an EEG signal (adjusted by a factor of 256) so we cannot use the trick to have it come up on a meter only when the is invoked. This is kinda unresolved. Mode 4b allows to monitor EOP, but not concurrent with EIM (that’s Mode 4a).

Mode 4a (4 blinks “EIM”) (all devices) – 4ch 256sps/45Hz, 2 channels of EEG, 2 channels of EIM (continuous)
Mode 4b (4 blinks “EOP”) (all devices) – 4ch 256sps/45Hz, 2 channels of EEG, 2 channels of EOP (latter need to be multiplied by x256 to get correct voltage of offset)

Note that Modes 4a and 4b can only be invoked from the BioExplorer Wiz Window. (But that’s what everyone is using right?)

So where EIM is desired, Mode 4a is preferred over using the function solution. Except is where using tablets and processor load is an issue.


If you want EIM and EOP (your question) then the best solution is to use Mode 4b and have continuous EOP on ch 3 & ch4, then use the function to pull up EIM when needed – the EIM appears on a source object configured for HEG, so is only active when the is active. Thus, the design has 6 source objects

– source 1: WIZ ch1 (EEG)
– source 2: WIZ ch2 (EEG)
– source 3: WIZ ch3 (EEG) (ch1 EOP) (multiply by x256)
– source 4: WIZ ch4 (EEG) (ch2 EOP) (multiply by x256)
– source 5: WIZ ch1 (HEG) (EIM ch 1 – active only when active)
– source 6: WIZ ch2 (HEG) (EIM ch 2 – active only when active)

Note: starting & stopping

– to start click .
– to stop click (ie EOP)

If continuous EIM is preferred over continuous EOP, then a good solution is difficult


BioExplorer designs for the WIZ are MODE SPECIFIC. For example, the wiz sources used above do not make sense in Mode 2 (“EEG”). The core part of the design would still work – you will have eeg on source 1 and 2 – but nothing on source 3 and 4 (Mode 2 is two channel).

<<<<< Thus when naming the design, the Mode should constitute the first part of the name>>>>>

EG: “wiz_Mode4b+EIMhelper_EEG_2ch_Aplha_Theta_Video.bxd” (“4b” defines continuous EOP)

As an aside, BioEra has the ability to send commands to the Wiz as part of the design. Thus in the above instance, the BioEra design can be set up to _automatically_ send the command to the Wiz to force Mode 4b when the design opens. It would be nice to have that in BioExplorer too. Maybe one day.

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