The DS4 has been developed to meet the needs of life 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 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.
Unique “Inactivity Sensor” Prevents Unwanted DC Stimulation
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±0.15% 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 DC power supply to power the input control circuitry and readily available/inexpensive batteries to provide the opto-isolated stimulus voltage source. The DS4 can be fitted into a 19″ rack mounting frame (D121-11) which can hold up to two DS2A’s, DS3’s DS4’s or DG2A’s.
- External voltage control permits software defined waveforms
- Isolated constant current output for low noise
- Minimal zero crossing distortion
- Inactivity sensor significantly reduces leak currents
- Battery test sockets
DS4 – Bi-phasic Stimulus Isolator
Publications which cite use of the Digitimer DS2A can be found on Google Scholar.
- Power Supply Adaptor
- Mains Lead
- Operator’s Manual
- One set of batteries
- Pair of output plugs (NL985P)
- DS4-BATT – Set of Replacement Batteries
- NL985P – Output Plugs