The DS8R is a new multi-mode, discrete pulse, constant current stimulator for human research studies involving nerve and muscle stimulation via surface electrodes. It features a high compliance voltage and can be triggered by a TTL compatible input, contact closure foot/hand switch or front panel “single-shot” button. The DS8R can deliver monophasic or biphasic pulses of up to 2ms duration, with an output range of 2mA to 1000mA (from 400V), however the actual current achieved will be restricted by a pulse energy limit of 300mJ per pulse and the skin/electrode resistance. Most importantly, the new DS8R incorporates features that allow external “on the fly” control of stimulus pulse parameters. A special edition firmware can also be provided for researchers interested in stimulating at higher frequencies (10kHz) than the standard unit permits. Protocols inspired by “Russian” stimulation” methods are possible with this optional firmware.
Biphasic Charge-balanced Output
The DS8R Biphasic Constant Current Stimulator, has two pulse modes, enabling stimulation using monophasic or biphasic rectangular pulses. Additionally, in biphasic mode the DS8R allows for both symmetric or asymmetric charge-balanced stimuli through implementation of an adjustable stimulus/recovery phase amplitude ratio. Biphasic charge-balanced stimulation offers certain advantages over monophasic stimulation, as it prevents the potentially harmful electrochemical changes which occur under stimulation sites and is reported to be more comfortable for the subject during long periods of stimulation. The recovery phase ratio can be adjusted from 10% to 100% in 1% increments. As illustrated below, at 100% the two phases are identical in terms of duration and amplitude, but as the ratio is reduced from 100% the amplitude of the recovery phase decreases, while its duration is extended to preserve charge balancing.
External Control Capabilities – Software (via USB) and Analogue Voltage Input
Researchers often want to adjust stimulus settings (current and duration) during a stimulation protocol and with the arrival of the DS8R, such control becomes a reality. While the DS8R can operate as a standalone isolated stimulator with full control via the front panel, settings can also be modified using Windows PC control software (supplied) via a USB interface. This software 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 software packages.
Pulse current amplitude can be more simply controlled via an analogue voltage input (BNC) on the rear of the DS8R. Using this method of control, the DS8 monitors the voltage applied at this input (0-10V) and adjusts the stimulus current proportionally with this voltage as each trigger input is detected. Note that the control voltage signal does not define the shape of the output pulse, it is merely used as a proportional representation of the output stimulus current
The DS8R is suitable for human research applications, but because the maximum pulse energy of 300mJ exceeds the 50mJ limit imposed by the international standard for diagnostic stimulation devices, we are not seeking medical device certification for the DS8R. If you have a requirement for a medically certified equivalent of the DS8R, please contact us to express your interest.
- Current range 2mA to 1000mA, in 0.1mA steps, from up to 400V (note the DS8R cannot deliver stimuli <2mA)
- Pulse duration range 50-2000µs
- Optional special edition firmware allows triggering at up to 10kHz. Please contact us for details
- Biphasic Output – Charge-balanced symmetric or asymmetric
- Adjustable inter phase interval (1-990µs)
- External control via supplied PC software/USB connection (includes API)
- Analogue Control of Stimulus current
- Output connection accessories, including plugs and cables and electrodes are also available.
1. The DS8R is limited to a maximum pulse energy of 300mJ, why was this value chosen?
The 300mJ/pulse limit is present in the EN 60601 international standard and is applicable to medical electrotherapy devices. While the DS8R is intended for research use only, we felt it was prudent to limit the DS8R to a pulse energy that could be applied to a comparable medical device.
2. Can the DS8R produce non-rectangular stimuli?
No, the DS8R is a triggered pulse stimulator, so the output can only be rectangular in shape. If you need to stimulate with non-rectangular waveforms, please see our DS5 Bipolar Current Stimulator.
3. I am thinking of using the DS8R for human sensory threshold studies, will be it be suitable?
The DS8R has a minimum pulse amplitude of 2mA and because of this we would not recommend it for this application.
4. Is it possible to trigger the DS8R from the virtual front panel software?
Yes, but because of the temporal unreliability of USB communication, we limit the frequency to no more than 10Hz when triggered by the button in the software or via the API.
5. I have seen reports of the DS8R being used for “Russian Stimulation” protocols, is this possible?
The standard DS8R can be triggered at a maximum frequency of 1000Hz, however, we have provided a modified firmware to some users which allows the DS8R to be triggered at 10kHz, allowing it to deliver bursts of biphasic pulses with 50us phase durations and <1us phase intervals. Please contact us if you have an interest in this non-standard firmware.
DS8R Software Install
The latest version of the DS8R firmware can be downloaded from the link below. This firmware is only compatible with serial numbers 29 and higher. Upgrade instructions are included within the manual, but can also be requested from Digitimer or one of our representatives.
DS8R Sales Literature Download
As the DS8R is a new product we do not have any publications yet.
- Mains (Power) lead
- Operator’s Manual
- GUI Software (USB Flash Drive)
- USB Cable
- D185-HB4 Output Extension Cable
- D185-OC1 Output Connection Plugs
- DG2A Train/Delay Generator
- DS7A-HS1 Hand-switch for remote triggering
- Electrodes & Accessories