DS2A

Digitimer

Constant Voltage Stimulator/Stimulus Isolator

The DS2A from Digitimer is a battery-powered, low-noise constant voltage stimulator designed for in vivo and in vitro electrophysiology experiments. It delivers monophasic voltage pulses with exceptional precision and stability, making it an ideal tool for stimulating neurons, peripheral nerves, or muscle fibers without introducing electrical noise into sensitive recordings.

Because it is fully isolated from its trigger source and ground, the DS2A minimizes interference and cross-talk - making it particularly well-suited for experiments involving simultaneous stimulation and recording.

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Precise, Reproducible Stimulation

Voltage Range: Selectable output range of 0–9V or 0–99V
Pulse Duration: Adjustable from 20µs to 2s (internally or externally via TTL control)
Polarity Switch: Easily reverse stimulus polarity from the front panel
Battery Powered: Isolated output driven by internal alkaline batteries to ensure clean, reproducible pulses
Trigger Options: Supports external TTL gating (e.g., from Digitimer's DG2A) or manual single-pulse triggering
Battery Check Sockets: Quickly verify battery status before starting a session

The DS2A’s robust yet compact form factor makes it ideal for both benchtop and rack-mounted configurations. It fits neatly into the D121-11 19″ rack frame, which can accommodate up to two units (e.g., DS2A + DG2A, or dual DS2As).

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DS2A vs. DS3: Constant Voltage or Constant Current?

While the DS2A and DS3 share a similar form factor, front panel layout, and triggering options, they differ fundamentally in the type of stimulation they deliver:

Feature	DS2A	DS3
Output Type	Constant Voltage	Constant Current
Output Range	0–9V / 0–99V	0–10mA / 0–100mA
Typical Use Cases	Direct voltage stimulation of tissues	Current-controlled stimulation of nerves
Power Source	Internal batteries	Internal batteries
Output Polarity	Selectable via switch	Selectable via switch
TTL Gating / Trigger Input	Yes	Yes
Ideal For	Applications where electrode impedance is stable	Applications requiring consistent current regardless of load

Choosing Between DS2A and DS3:

If your experiment requires a precise voltage waveform, such as when electrode impedance is known and stable, the DS2A is the ideal choice. However, if your priority is delivering a consistent current stimulus—especially where tissue or electrode impedance may vary—the DS3 Constant Current Stimulator is recommended.

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Pulse Duration	Range: 20µs to 2s. One dial allows continuous adjustment from 2 to 20, while another selects the range (10µs, 100µs, 1ms, 10ms, 100ms, or external source). Internal values have ±10% accuracy.
Output Terminals	A pair of 2mm touch-proof sockets on the front panel spaced at 0.75”.
Polarity Switch	Normal: Red output terminal positive. Reverse: Red output terminal negative.
Indicator	An LED operates for the duration of each output pulse.
Compliance	90V from 10 × 9V batteries. Reduces to 87V at top of each output (DS3 only) range. Battery voltage may drop to ~6V with “old” batteries.
Overload	Automatic circuit (DS2A only) reduces output pulse duration to <10µs when current >50mA is detected.
Single Shot	Single-shot push button provided. Operates regardless of trigger input.
Trigger	Requires positive pulse of 3V to 20V. Input current varies from 6mA to 62mA. Pulse duration should be ≥4µs.
Trigger Isolation	Optical coupling with less than 3pF capacitive coupling between source and stimulator circuitry.
Batteries	11 × PP3, IEC-6R61 style batteries. Current is drawn only during pulse. Battery test sockets included.
Mounting	One or two stimulators mountable in a 19” rack using model D121-11 frame (from Digitimer Ltd).
Dimensions	Panel: 190mm × 110mm. Depth: 80mm over knobs.
Weight	800g complete with batteries.

Important Note: This product is for research applications only. Not a medical device as defined in Regulation (EU) 2017/745 (EU MDR), Swiss Medical Devices Ordinance (MedDO, SR 812.213), or FDA 21 CFR Part 860. Not designed or intended to be used for diagnosis, treatment of disease or any other medical purposes.

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