Battery Powered Constant Current or Constant Voltage Stimulators

Brief pulses of electricity are used in various biomedical research applications as a stimulus to excite nerve or muscle fibers.  In EP research, electrical stimulation is commonly used to elicit somatosensory evoked potentials.  Several factors need to be considered to chose the right stimulator for your application:

  • In order to minimize artifacts introduced into electrophysiological data, it is desirable that the stimulator should be electrically isolated both from ground and from the trigger device.
  • The voltage required to send current through tissues can vary greatly, making it important to have control over the stimulus driving force.
  • Large impedence variations during an experiment can result in loss of the stimulus.  In this event, a constant current stimulator may be more suitable.

Both of the stimulators we offer meet these important criteria.  Review the differences highlighted below to chose the stimulator that best meets your experimental needs.

DS3 – Constant Current

DS3 provides constant current stimulation with accurate and reproducible stimulus characteristics, switchable polarity, variable output and duration ranges (20µs to 2s), an external pulse duration control through the BNC trigger input and a single-shot button, which operates irrespective of trigger inputs. The case is manufactured from insulating material, and power is provided by standard batteries. Current is only drawn during pulse delivery. Accurate and reproducible stimulus characteristics, switchable polarity, variable output and duration ranges, external pulse duration, case manufactured from insulating material, power provided by standard batteries.

SD-SS-ELDS3

DS2A – Constant Voltage

DS2A provides constant voltage stimulation with accurate and reproducible stimulus characteristics, switchable polarity, variable output and duration ranges (20µs to 2s), an external pulse duration control through the BNC trigger input and a single-shot button, which operates irrespective of trigger inputs.  The case is manufactured from insulating material, and power is provided by standard batteries.  Current is only drawn during pulse delivery. Accurate and reproducible stimulus characteristics, switchable polarity, variable output and duration ranges, external pulse duration control through the BNC trigger input, a single-shot button which operates irrespective of trigger inputs, case manufactured from insulating materials, power provided by standard batteries.

SD-SS-ELDS2

DS4 – Computer Controlled

The DS4 has been developed to meet the needs of laboratory scientists who require a stimulus isolator that can output a bi-phasic isolated constant current stimulus in response to an external command voltage signal, provided by a computer DAC via software. Such a requirement is already met by our NeuroLog System in the form of the NL512 Biphasic Buffer and NL800A Stimulus Isolators, but the DS4 provides our first standalone device to meet this need.The DS4 accepts a variety of voltage input ranges (±1V, ±2.5V, ±5V and ±10V) and produces a constant current stimulus output in 4 overlapping ranges (±10μA, ±100μA, ±1mA and ±10mA) from a compliance voltage of ±48V. In addition, the DS4 has a GATE input which allows multiple DS4’s to be connected to a single analogue voltage source, with each DS4 being digitally enabled, separately.

One of the problems with stimulators that make use of an external voltage source to define a stimulus waveform is that small offsets or noisy baseline signals from the DAC’s used to drive them can result in unwanted battery drain or perhaps worse, low amplitude stimulation. The DS4 uses a special “inactivity sensor” to monitor the input voltage and disable the DS4 output if this voltage falls within 0±0.2% of the full scale value for a user selectable time period of 100ms, 200ms, 1s or 2s. Unlike other devices which only produce an output when the input voltage exceeds a threshold value, this “inactivity sensor” reduces battery usage and damaging “leak currents” during infrequent stimulation, while at the same time maintaining low levels of zero crossing distortion for repetitive waveforms.

The DS4 uses an external power supply to power the input control circuitry and readily available/inexpensive batteries to provide the opto-isolated stimulus voltage source.

DS4350

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