The unit can be triggered fast enough to allow >99% “on” time, but the “off” time must >20 microseconds – so, very fast!

Neither the DS2A, DS3 nor DS4 have medical device directive (MDD) certification and have not been designed for safe human use. We offer a range of medical device compliant stimulators for patient connection as well as a range of stimulators designed for safety in human research studies.

Yes and no. The DS3 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.

Our stimulators are not classed as MRI safe, as all of them contain ferrous materials which means they cannot be used within a magnetic field. However, as long as they are located beyond the reach of magnetic field or in the scanner control room they may be used. It is important that MRI compatible electrodes and cables are used within the scanner room.

The trigger button has no effect of trigger frequency. It is designed to allow the user to press and hold the Trigger Button to deliver a continuous single stimulation pulse while it is held down. This can be useful for electrical lesioning of a recording site once an experiment is complete.

Absolutely. The output of the DS2A or DS3 is optically isolated from the trigger inputs, so there is no need to worry about what your trigger source is, or how it is grounded.

Correct, you should program your DAQ interface to deliver trigger pulses @ 10Hz for 30s via a digital output. The DS2A will trigger on each rising edge and the stimulus duration will be set to 1ms using the controls on the DS2A front panel, with the voltage set to 20V.

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.

Yes, this is quite simple to setup and has been summarized in an application note available in the downloads section.

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, there are two simple methods. (i) The DS3 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.