configure BioExplorer for the Q-wiz

This is an introductory description. The full description of Wiz devices can be found under the Manuals tab.

The Q-wiz is a 4 channel bio-signal acquisition device. It supports a number of Modalities (EEG, ECG, EMG, SCP, Othmer, nIR HEG, pIR HEG, pulse oximetry) both wirelessly and via direct USB connection, although the Q-wiz is principally intended to operate as a USB-direct device. It has an interface to 19/21ch EEG caps, allowing for electronic switching of up to four sites tothe Application. It also has direct support for the van Deusen 4ch EEG assessment procedure. It supports continuous electrode impedance measurement and electrode offset voltage measurement. ExG signals can be AC or DC coupled, and the two electrode references can be electronically linked. It also supports automatic calibration (“baselining”) for HEG signals.

Functions on the Q-wiz are controlled by two buttons, a Mode button and a Link/Freeze button. Note however that all functions, indeed some additional functions as well, can be controlled from the Application, whether that application be BioExplorer, BioEra, EEGer, or Wiz Central. In general, it is easier to command the Wiz from the Application rather than navigate many functions applied to just two buttons. As a consequence this introduction will focus on commanding the Wiz from the Application. Information on using the buttons on the Wiz can be found in the User Manual.

“Mode” refers to the characteristics of the channels used to transport the bio-signals from the Wiz to the Application. Mode defines the sampling rate and the number of channels. “Modality”, on the other hand,  refers to the different types of bio- signals supported, such as EEG, EMG, and HEG. Different modalities place different demands on the channel supporting them, thus for example, HEG can be supported on a low sampling rate channel and EMG demands a high sampling rate channel. The Wiz provides different Modes to optimally support different Modalities on up to four slots available for sending bio-signals to the Application.

There are two formats for data sent over the channel to the application. One format is used for ExG (ie EEG, EMG, ECG, SCP, Offset) and another for HEG & EIM (electrode impedance measurement). The choice of data format is transparent to the user and would not need to be mentioned here except that the design needs to to know which outputs (EEG or HEG) are active. In general, the choice of EEG/HEG is determined by plugging in HEG (nIR, pIR or pulse) headbands/sensors. The default formats are EEG, however when HEG headbands are plugged in, the format of the data is automatically changed to HEG and, importantly, the Application is advised that this change has occurred. Thus, where a design has elements connected to both EEG & HEG Source outputs, those elements will be activated in turn as the HEG headband is plugged in and then removed.

Since the Wiz remembers certain parameters including Mode, in the most common usage scenario of  single channel & single modality, operation reduces to

  • connect the sensors or plug in the headband,
  • turn on the Wiz, and
  • hit the play button on the Application.

Complexity is hidden by communication between the Wiz and the Application: in this scenario, the bio-signal will always appear on the first slot, it’s data format will be automatically set based on whether there was a HEG headband or sensor connected or not,  and in the case of HEG modalities, the Wiz will auto-baseline.

The Modes available are listed below. The Mode light on the Wiz will blink once for Mode 1, etc.

Qwiz_layout01

 

Q-wiz Modes

<Mode 0> program mode – used to upload new firmware or interrogate firmware version number

<Mode 1> 2ch x 32sps – used for HEG only (and EEG protocol processing – future)

<Mode 2> 2ch x 128sps – Hi resolution EEG and HEG

<Mode 3> 2ch x 512sps – EMG, ECG and SCP (and EEG if mixed modalities) – higher bandwidth, lower sensitivity.

<Mode 4> 4ch x 256sps – used for 4ch EEG training & assessment, or for multi-modal operation

<Mode 4a> 4ch x 256sps – ch 3 & 4 used for electrode impedance of ch 1 & 2 – invoked by command from the application

<Mode 4b> 4ch x 256sps – ch 3 & 4 used for electrode offset of ch 1 & 2 – invoked by command from the application

In each Mode, the content on the two/four slots being sent to the Application depends on which sensors are active (ie plugged into the Wiz). In general, the design controlling the Application trains a particular Modality and therefore expects a particular Mode. The Mode expected should constitute part of the name of the design. The user should then set the Wiz to the Mode expected by the design. The table below is provided for reference.

configurationSlot 1Slot 2Slot 3Slot 4Comment
Mode 1/2/3
no headband sensedEEG1EEG2
nIR sensedNIR1NIR2
nIR & pIR sensedNIR1PIR1
pIR sensedPIR1EEG1
pulse sensedPULS1EEG1
pIR & pulse sensedPULS1PIR1
Mode 4
no headband sensedEEG1EEG2EEG3EEG4
nIR sensedEEG1EEG2NIR1NIR2
nIR & pIR sensedEEG1EEG2NIR1PIR1
pIR sensedEEG1EEG2EEG3PIR1
pulse sensedEEG1EEG2EEG3PULS
pIR & pulse sensedEEG1EEG3!PULSPIR1
Mode 4a
Q/E/U-wiz:EEG1EEG2EIM1EIM2continuous electrode impedance measurement
H/X-wiz:HEG1HEG2IR1RED1HEG (nIR or pulse) components (infrared, red) extracted
Mode 4b
Q/E/U-wiz:EEG1EEG2Offset 1Offset 2continuous electrode offset measurement
H/X-wiz:HEG1HEG2IR1Red1

The lights on the Wiz can be used to confirm that commands sent from the Application have been received:

Indicator 
Transmit (blue)
On steadysending to Application via USB
On blinksending wirelessly
Off blinknot transmitting to Application (ie Program Mode)
4 blinksacknowledging command received for Application
No of blinkswireless channel number
Mode/Good (green)
Onno EEG lead off, and/or nIR full signal strength, and/or pIR valid reading
OffEEG pair off, or nIR not full strength, or pIR reading out of range
Fast BlinkEEG single electrode off
No of blinksMode 0/1/2/3/4 = Program/32sps(2ch)/128sps(2ch)/512sps(2ch)/256sps(4ch)
Link/Freeze(blue/green)
On blueEEG baseline frozen (DC coupled)
Off blueDC removal - EEG low frequency response ~0.2Hz
On greenEEG References linked - only one Reference electrode required
Off greenEEG References independent - two References required for 2 eeg channel operation
HEG (yellow)
Onwhen nIR, pIR or Oxi headband sensed
Offno headband sensed, all 2/4 channels used for EEG
Blinkwhen nIR/pIR/pulse baseline search for nominal value of 100 is under way

The Wiz Window in BioExplorer has the following functions for commanding the Wiz:Wiz_Command_BioExplorer

  • Main
    • Power – turn Wiz on & off
    • EEG Link References – electronically connect the two eeg reference electrodes
    • EEG Freeze Offset – instantly directly couple the ExG signal, DC offset removal is inhibited
    • HEG Calibrate – initiate search for the HEG nominal value of 100
  • Mode
    • Program – Mode 0:  set this mode to update firmware or interrogate version number
    • HEG – Mode 1: set this mode for HEG signals to minimise the load on the PC processor
    • EEG – Mode 2: set this mode for EEG and minimum load on the PC processor
    • ExG – Mode 3: set this mode for ECG. EMG, SCP and Othmer protocols, hi bandwidth and reduced sensitivity, Also set “Freeze” for SCP, Othmer & possibly ECG
    • EEG+Impedance – Mode 4a: 2ch EEG and continuous electrode impedance measurement in ch 3 & 4
    • EEG+Offset – Mode 4b: 2ch EEG and continuous electrode voltage offset measurement in ch 3 & 4
    • 4Ch – Mode 4: 4ch eeg or multipmodal operation
  • Helper functions used occasionally
    • Off – revert back to normal mode
    • Electrode Impedance Check – interrupt the eeg signals to test for electrode impedance
    • Electrode Offset Check – interrupt the eeg to test for electrode offset voltage
    • Electrode-sense Off – turn of the current used to sense electrodes falling off to improve accuracy of DC coupling
    • Test Tone – inject a test sequence of 4,8,16 & 32Hz at 1 second intervals to check Wiz is working OK
  • USB+Wireless
    • USB Only – turn off wireless
    • 1…8 – turn on simultaneous USB and wireless, the latter allows monitoring of the eeg by a monitoring station

Checking the validity of bio-signals

There are a few things in the Wiz to enable you to check it’s health.

  • ExG  (applicable to EEG, ECG, EMG and SCP)

First item is the “Test Tone”  Helper function. This is available in the Wiz window in BioExplorer under Helper functions:  Test Tone.

If ExG is active, the Test Helper function injects a tone right at the input of the Wiz, so in general, if the Test function is working, then the Wiz is working. If the Test signal is fine, but the EEG is flat-lined, then the first thing to check is that “Freeze” blue light is off. Freeze is switched on for working with SCP (& ERPs), Othmer low frequency protocols, and possibly ECG. Activating the Freeze function puts the Wiz into its DC-coupled mode. This means that the offset removal that is normally in place, acting to return the EEG signal to an average of 0 microVolt is deactivated. If Freeze is switched-on whilst the EEG is out of range, not yet having fully restored itself to an average of 0 microVolt, then it will stay out of range indefinitely. That is, the EEG will be flat-lined. For this reason the Freeze state is not remembered by the Wiz – each time the Wiz is started, it starts with Freeze off.

Also, if using one-channel EEG designs, you must use Channel 1 (aks 1+/1-, aka Left). If you use Channel 2 (or 3 or 4) without using Channel 1, then the feature of actively suppressing 50/60Hz interference is lost.

If these conditions are satisfied, then one should look to problems with the electrodes themselves.

In relation to electrode performance there are several layers of defense.

  • First, the Red/Green information in the Status Bar of BioExplorer, give “electrode off” indications. This will actually identify which electrode has fallen off using the following code
    • steady red light – both electrodes are off (or that channel is not in use)
    • flashing red light – one of the pair of electrodes is dislodged

Linking reference electrodes can then distinguish which of the pair of electrodes is dislodged

    • if the flashing red light persists when electrodes are linked, then it is the active electrode that has dislodged
    • if the flashing red light goes steady green, then it is the reference electrode that has dislodged.
  • Second, there are two Helper functions related to checking electrodes:
    • “Impedance Check” and
    • “Offset Check”.

Electrode impedance is a measure of the goodness of the contact of the electrode with the skin. Poor contact will result in a noisy EEG and quite possibly a large increase in 50/60Hz power line interference which too can lead to flat-lining. EIM is a measure of the impedance of an electrode pair, not a single electrode. So values under 20kOhm can be considered good and up to 50kOhm is quite serviceable. Offset Check is a measure of the voltage generated by the metal electrode together with an electrolyte  (the paste) onto the skin. All metals will generate this voltage with Ag/AgCl electrodes having the lowest voltage. EEG systems are designed to tolerate this relatively large voltage, however gold-plated electrodes, when the gold plating wears or is otherwise compromised, exposing a different base metal, produces a particularly severe offset voltage that can cause the EEG to intermittently flat-line. Gold electrodes are not recommended. The Wiz can tolerate offset voltages +-250mV and so should not be an issue if gold electrodes are not used.

Mode 4a and 4b allow EIM and Offset respectively, to be monitored continuously. However if not in either of these Modes, for instance if using Mode 4 for 4ch EEG, then EIM and Offset measurement (in this case for 4 channels) is invoked by selecting the Helper function Check Impedance and Check Offset. Once the measure is obtained, then Helper functions are set to Off, and the normal ExG operation is restored.

  • HEG

In relation to HEG, the Helper Test Tone function puts out a test tone of approximately 99.5 and 100.5, alternating every second. This is not as complete a test as the Helper Test for EEG, but does check most of the HEG circuitry.

In relation nIR HEG, the Helper Test also tests the signal sent to the nIR headband. In normal use, the Red and Infrared lights on the headband are switched rapidly making it impossible to see whether the infrared light (being largely outside the visible spectrum, and so very dim) is lighting or not. With the Test Helper, the signals sent to the headband are a slow flash of the Red and Infrared light so that it becomes possible to perceive that the infrared light is illuminating. If either light is not working, then a return-to-factory repair is required.

 

 Q-wiz EEG Cap Interface

Cap_Command_BioExplorer

The Q-wiz features an interface to a 21 channel EEG cap. Electrocap and Deymed caps are compatible, altho the latter is compatible for 19-ch montages only.

The Cap can be used for assessment or training, and electronic multiplexing of 21 channels of the Cap onto 4 slots of the Q-wiz is controlled by BioExplorer’s “Multiplexer” tab in the Wiz Window. Switching of sites occurs on the fly, without the need to halt the Wiz.

Since there are 21 EEG sites available to the CAP and just 4 slots to the PC Application, there is a choice of which site is to go to which slot. Each Slot can accept one or more of 8 possible Cap sites. Thus we speak of “multiplexing” Cap sites onto available slots, and of a “mapping” of sites onto slots.

The Cap interface sits across the normal electrode inputs, so both the Cap interface and the normal electrodes can be used at the same time, however in general one should use either the Cap interface or the normal electrode interface but not both. Linking of electrode references by toggling the “Link” button applies equally to the normal electrode input and the references provided by the EEG Cap, which are normally ear-clip electrodes.

Since each slot chooses one of 8 electrode sites, not all combinations of sites is possible, however the possibilities do include the sites necessary for the Brainmaster and TLC mini-Q assessment procedures.

BioExplorer directly supports the TLC assessment procedure with the “TLC” suite of buttons at the bottom of the Wiz Multiplexer Window.