An Explorer system uses a modular design where individual components can be added, removed or replaced for specialized applications. The most basic configuration consists of a processor and one or more Front Ends. I/O modules can be connected to provide analog and digital inputs and outputs for communicating or controlling external devices.

The system can be powered by a wall outlet, or use the internal battery. An external battery is available to extend operational time. The system can be controlled by a computer using an ethernet cable or via WiFi to eliminate cables. It can also be preprogrammed to run independently, and the front buttons can be programmed to load custom software or provide feedback during operation.

For higher channel counts (up to 1024), or for applications such as hyperscanning, two processors can be linked together and operated as a single system.

The Processor

The Explorer line currently has three different processors, the Nomad, the Quest HD, and the Quest HD+Stim. The main difference between these processors is the Front Ends (FEs) they can communicate with, dependent on their bandwidth (sampling rate) and stimulation capabilities. The Nomad is capable of controlling all FEs, while the Quest processors are limited to FEs with lower sampling rates. The Quest Processors also come in two versions that determine maximum channel count; 64 or 256 channels. The Nomad processor is capable of recording 512 channels. The table below shows all processor variants and which FEs they can control.

Nomad Processor Quest HD 64ch Processor Quest HD 256ch Processor Quest HD+Stim 64ch Processor Quest HD+Stim 256ch Processor
Maximum Channels 512 64 + 1 Physio FE 256 + 2 Physio FEs 64 + 1 Physio FE 256 + 2 Physio FEs
32ch EEG
128ch EEG
32ch EEG+tES
128ch EEG+tES
32ch Macro
128ch Macro
32ch Macro+Stim
128ch Macro+Stim
32ch Micro2
32ch Micro2-HV
32ch Micro2+stim
32ch Micro2+stim HC
16ch Differential Physio/EMG
32ch Single-Ended Physio/EMG

Front Ends

The Explorer line offers several different Front Ends with varying specifications to provide ideal recording and stimulation capabilities for different modalities. Multiple types of FEs can be connected to the same processor to allow for multimodal recordings.

Every Explorer processor has four ports to connect to Front Ends. Each port can connect to between one and four 32 channel FEs, or a single 128 channel FE, with the total number of channels possible determined by the processor type (shown in the table above).

There are four main families of front ends, the Micro, the Macro, the EEG and the Physio, each with different specification to cover different types of recording modalities. All but the Physio also have versions capable of stimulation on every channel.

The Micro was designed for high-resolution, invasive recordings. Capable of recording single units, it works very well with high-impedance microelectrodes. The Micro+Stim is capable of stimulating on all channels simultaneously, and is limited to lower current levels compared the Macro, making it more suitable for microelectrodes more commonly used in research.

The Macro was designed to be more in line with standard clinical invasive electrodes. It has a lower maximum sampling rate compared to the Micro, and a more focused bandwidth to optimize it for applications such as high-resolution ECoG or sEEG. The Macro+Stim maximum stimulation current is higher to match common clinical stimulators, while limiting current flow to one anode and one cathode per 16 channel bank to prevent excessive discharge. However, due to the fast switching times common to all Ripple Neuromed stimulating front ends, all channels can be effectively stimulated at once by using interleaved pulse trains.

The EEG was designed for noninvasive surface electrodes. As the name implies, it is designed with EEG specifically in mind, however it is suitable for any surface recordings that do not require bipolar or true differential referencing. The stimulation version, the EEG+tES, is designed for stimulation from surface electrodes, such as transcranial stimulaiton (tCS), transcutaneous nerve or spinal stimulation (TENS, TSS).

The Physio was designed specifically with electromyography in mind, although can be used for any type of electrophysiology from the body, such as ECG or noninvasive peripheral nerve recordings. It comes in both a 32 channel shared reference version, as well as a 16 channel bipolar version. The Physio does not have a stimulating version.

Micro Macro EEG Physio
Recording
Channels 32 32 or 128 32 or 128 16 bipolar or
32 shared reference
Resolution 16-bit 24-bit 24-bit 24-bit
Max Input Range ±12mV ± 2V ± 2V ± 187.5mV
Sampling Frequency Up to 30 ksps Up to 7.5 ksps Up to 7.5 ksps Up to 7.5 ksps
Bandwidth
(stim version)
0.1Hz – 7.5kHz
(1Hz – 7.5kHz)
DC – 2 kHz
(0.03 Hz – 2kHz)
DC – 2 kHz
(DC – 2kHz)
DC – 2 kHz
(N/A)
Stimulation +stim version +stim version +tES version Not available
Stimulation Range (per channel) Up to ± 1.5mA Up to ± 15mA Up to ± 2mA N/A
Pulse Width Minimum 1µs 33µs 33µs N/A
ompliance Voltage ± 8.5V ± 9 to 30V (configurable) ± 9 to 30V (configurable) N/A

I/O Modules

Three different I/O modules are available to provide analog and digital inputs and outputs. A condensed module containing both analog and digital inputs and outputs is available to provide a limited number of both analog and digital ports in a single package for better mobility. For applications in which only analog I/O, or only digital I/O is needed, or if a greater number of analog channels is needed, modules containing only analog and only digital inputs and outputs are available.

The Analog I/O module can be used independently or at the same time as the Digital I/O module. The Analog + Digital I/O module cannot be used with another I/O module.

Analog I/O Module Digital I/O Module Analog + Digital I/O Module
Analog Inputs 4x ±5V, SMA
24x ±5V, Micro-D
2x ±2.5V, 3.5mm jack
None 4x ±5V, SMA
2x ±2.5V, 3.5mm jack
Analog Outputs 4x ±5V, SMA
24x ±5V, Micro-D
4x ±2.5V, 3.5mm jack
None 4x ±5V, SMA
2x ±2.5V, 3.5mm jack
Digital Inputs None 4x SMA
16x Micro-D
2 Strobes
4x SMA
16x Micro-D
2 Strobes
Digital Outputs None 4x SMA
16x Micro-D
4x SMA
16x Micro-D
Dimensions 72 mm x 95 mm x 14.4 mm 59 mm x 92 mm x 14.4 mm 59 mm x 92 mm x 14.4 mm

Mains Power and Ethernet Connectivity

Each Explorer processor comes with an adaptor for connecting to a wall outlet for uninterruptable, wired power. The adaptor also includes a standard Ethernet jack for wired communication to a computer or network. For wireless operation, Explorer processors include an internal battery, internal storage, and WiFi communication. An external battery pack is available to extend wireless operation. Depending on usage, the internal battery lasts around two hours, while the external battery lasts about four. The external battery packs are hot-swappable to allow for uninterrupted continuous wireless recording.

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