The DS2A Isolated Constant Voltage Stimulator is a low noise solution for electrical stimulation of in vivo and in vitro preparations, in order to excite neurons, nerves or muscle fibres. Battery powered and isolated from its trigger source and ground, the DS2A is designed to deliver precisely adjustable voltage pulses, without introducing noise into electrophysiological recordings. The DS2A will output monophasic voltage pulses of up to 100V, which are widely adjustable in pulse duration and amplitude.
DS2A Product Information
Application Note 1
Using two DS2A Isolated Constant Voltage Stimulators in series allows stimulation through the same electrodes with different pulse types.
Application Note 2
Using a DG2A Train/Delay Generator and two DS2A Isolated Constant Voltage Stimulators to produce a repetitive biphasic constant voltage stimulus.
Publications which cite use of the Digitimer DS2A can be found on Google Scholar.
The unit can be triggered fast enough to allow >99% “on” time, but the “off” time must >20 microseconds – so, very fast!
The DS2A does not have medical device directive (MDD) certification and has not been designed for safe human use. We offer a range of MDD compliant stimulators for human/patient connection.
Yes and no. The DS2A features an external “gate” input allowing externally derived trigger pulses to define stimulus duration. However, the output amplitude is always determined by the front panel setting of the stimulator. We recommend our NeuroLog system to those interested in using a computer generated waveform to define stimulus timing/polarity and strength.
Yes, there are two simple methods.
(i) The DS2A has the ability to be gated by an external pulse i.e. when external control of pulse duration is selected the output stimulus timing will be controlled by the trigger-in stimulus pulse. It should be noted that (with a 5V input pulse) there is only a very short delay of <2µs for the turn-on and <6µs for the turn-off. When a typical TTL pulse is used, which will only be about 3V, these are matched at 4µs each.
(ii) Alternatively, if a trigger pulse is not available or exact timing is not crucial (for instance when lesioning or injecting dye, there is a jumper which can be set to allow the unit to deliver a current for the duration the single shot button is held down. The internal “Single” jumper determines the output delivered when the “SINGLE” button is pressed (when “EXTERNAL” Duration is selected).
“MON” (factory setting) produces a very short pulse ~10µs when pressed.
“CONT” produces an active output for the duration of the press. This could be useful in dye marking etc.
The visible difference between the two units (apart from the colour!) is that the output control of the DS2A is defined in Volts while the output of the DS3 is defined in Amps. The actual stimulus passing through your preparation is measured in Amps in both cases and is dependent upon Ohms Law (V = IR). If your preparation has a variable impedance (R) and you are using a constant voltage (V) source such as the DS2A, then the actual current (I) passing through the tissue may vary considerably between each stimulus, which may not be a good idea if you want to apply reproducible stimuli. With the DS3, the constant current circuitry prevents variations in tissue impedance from altering the size of current applied (within the 90V compliance limit of the unit), leading to the stimulator equivalent of WYSIWYG – “What You Set Is What You Get”. Unfortunately there are no well defined rules governing the circumstances under which either stimulator should be used. If you are not sure and feel the need to evaluate either or both please contact us.
No, Digitimer no longer offers this service. Since the introduction of the new DS3 constant current stimulator, this unit is now offered to customers requiring a constant current version of the DS2A.
Yes, this is quite simple to setup and has been summarized in an application note available in the downloads section.