DS8RDigitimer
DS8R Bipolar Constant Current Stimulator
Introduction
The DS8R is an isolated, constant current stimulator for humanresearch studies involving nerve and muscle stimulation via surface
electrodes. It features a high compliance voltage and can betriggered and controlled by multiple external sources. The DS8R
can deliver monophasic or biphasic current pulses of up to 2ms
duration, with an output range of 0 to 1000mA* (from 400V).
Notably, the DS8R is the first of our stimulators to feature external“on the fly” control of stimulus pulse parameters, making it possible
for stimulation protocols to be semi-automated.
*The actual current achieved will be restricted by a pulse energy limit of 300mJ per pulse and theskin/electrode resistance.

Optional Biphasic, Charge-balanced Output
The DS8R has two pulse modes, enabling stimulation using
monophasic or biphasic rectangular pulses. Additionally, in biphasicmode the DS8R allows for both symmetric or asymmetric charge-balanced stimuli through implementation of an adjustablestimulus/recovery phase amplitude ratio. Symmetric biphasic stimulation is known to reduce the size of stimulus artefacts, whilebiphasic charge-balanced stimulation prevents the potentially harmful electrochemical changes which occur under stimulationsites during monophasic stimulation and is reported to be more comfortable for the subject during long stimulation protocols. In
asymmetric mode, the recovery phase ratio can be adjusted from 10% to 100% in 1% increments. At a setting of 100% the +ve
and -ve phases are identical in terms of duration and amplitude, but as the ratio is reduced from 100% the amplitude of therecovery phase decreases, while its duration is proportionately extended to preserve charge balancing.

Multiple Stimulus Control Capabilities
Increasingly, researchers want to adjust stimulus settings (current and duration) during a stimulation protocol and with the arrivalof the Digitimer DS8R, such control becomes a reality. While the DS8R can operate as a standalone isolated stimulator with fullcontrol via the front panel, settings can also be modified using Windows PC control software (supplied) via a USB interface. Thissoftware not only provides a Virtual Front Panel for the stimulator, but more importantly incorporates an API allowing the operator
to implement control from custom or commercially available acquisition and stimulus control software packages.
Pulse current amplitude can also be controlled using an analogue voltage signal via BNC socket on the rear of the DS8R. The
DS8R monitors the voltage applied at this input (0-10V) and adjusts the current amplitude as this voltage varies. Each time theDS8R recieves a valid trigger, the actual stimulus current will be determined by the amplitude of this analogue voltage signal. Notethat the analogue voltage signal does not define the shape of the output pulse, as all stimuli are rectangular in shape; it is merely
used as a proportional representation of the output stimulus current.

Enhanced 300mJ Pulse Energy Limit for Demanding Research Applications
In order to make the DS8R stimulator suitable for as many applications as possible, we have set a maximum pulse energy limit of300mJ, which is the same as the limit imposed on therapeutic muscle stimulators, rather than the 50mJ limit for evoked
potential stimulators, such as our DS7A/AH. Because the DS8R is designed for human research rather than diagnosis ortherapy, we are not seeking medical device certification for it, but if you have a requirement for a medically certified equivalent of
the DS8R, please contact us to express your interest.

DS8R
Bipolar Stimulator

DS8R
Manual Trigger Button & LED Indicator
Four Stimulus Settings Blister Buttons

Error/Fault LED

Colour LCD Display
showing stimulus settings,
pulse measurements andwarnings

Output Enable
Toggle Switch

4mm Touch-proof
Output Sockets

Multi-function
Control Dial

Current Amplitude Control(also sets maximum current limit)

External Analogue Voltage Control
TTL Trigger In

WindowsTM Compatible DS8R Virtual Front Panel
Each DS8R stimulator is suppled with WindowsTM compatible software whichenables all stimulator settings to be modified remotely from a PC. This software
also allows the operator to turn off the audible out of compliance indicator. AnAPI is embedded in this software, which has been provided for programmers
wishing to control the stimulator via third party acquisition or stimulus control
software.

Analogue Voltage InThe rear panel of the DS8R features a BNC socket that accepts a 0-10V
input, allowing an externally generated voltage signal to determine thecurrent amplitude (scaled to the set output range) each time the DS8R istriggered. The figure opposite illustrates how variations in level of thisvoltage will scale the stimulus output amplitude.

Stimulus Output

DS8R
Bipolar Stimulator

DS8R
Features Overview
Stimulus Output
Current Output: 0-1000mA, incrementing in 0.1mA steps; accuracy ±2%.
Pulse Duration: 50-2000µs, incrementing by 10µs steps; accuracy ±2%.
Interphase Interval: 1µs – 990µs in 10µs steps; accuracy ±2%.
Recovery Phase Ratio: 10%-100% in 1% steps; accuracy ±2%.
Current Amplitude Limit Range: 10mA to 999mA in 1mA steps.
Pulse Mode: Monophasic or Biphasic
Pulse Polarity: Positive/Negative/Alternating.
Compliance Limit: 400V
Energy Limit: 300mJ per pulse
Output Enable: On/Off Momentary action toggle switch
Connections: 4mm shrouded sockets (red and black) on 3/4" centres

TriggerMaximum hardware trigger rate is 1,000 pps (1 kHz); ±1%
Maximum software (USB) trigger rate is 10pps (10Hz); ±1%Front panel: Push button
Rear panel: 3.5mm mono jack socket for hand or foot switch (contact closure)
TRIGGER INPUT Electrical via Rear Panel BNC socket: Triggers: Logic signal (+3V to +15V) +ve edge, TTL
compatible. Minimum Pulse Duration is 5 microseconds.
SYNC OUTPUT Rear panel BNC, positive TTL pulse, 100µs ± 20% duration.

External Amplitude Control

Front Panel Indicators
TRIGGER LED - Amber, flashes for each trigger received
FAULT/ERROR LED – Steady Amber, indicating internal hardware fault. Flashing Amber, indicating firmware updatein progress.
LCD Display Showing:Set Current, Set Pulse Duration, Set Recovery Phase Ratio, Set Interphase Interval, Pulse Mode, Polarity Mode,
Amplitude Control Mode.
Pulse Measurements, including Current (mA), Energy (mJ), Impedance (Ohms), Voltage (V)Stimulus Output Status Indicators
USB Communication Indicator
Audible Out of Compliance Warning (optional mute)

The Digitimer DS8R is NOT a medical device and use is limited to human research applications

Digitimer Ltd
37 Hydeway, Welwyn Garden City, Hertfordshire, AL7 3BE, UK
Tel: +44 (0)1707 328347 Fax: +44 (0)1707 373153
E-mail: sales@digitimer.com
Website: www.digitimer.com
Last updated: 22/03/19

DS8R
Bipolar Stimulator

Digitimer reserves the right to change product specifications without notice.

Working input range: 0 to +10V (equivalent to 0 to 1000mA when Current Amplitude Limit is disabled).
Lag: 1ms (i.e. the DS8R will respond to amplitude changes at a maximum frequency of 1kHz)