DS8R – A New Tool for Sensory Threshold Stimulation

We are excited to announce a major upgrade to the DS8R Isolated Bipolar Stimulator, which can now deliver stimuli as low as 100µA, making it fully compatible with human research involving transcutaneous stimulation within sensory threshold levels. Digitimer strives for continuous product development and while the first iteration of the DS8R has already proved extremely popular in areas such as spinal cord injury rehabilitation research, kinesiology, cognitive neuroscience and psychology, its inability to stimulate at levels below 2mA was something we were keen to resolve.

Ensuring that a stimulator capable of delivering up to 1000mA could also operate reliably at levels below 1mA was a significant technical challenge. However, through implementation of some innovative hardware and firmware changes, our engineers identified a way to accomplish this.  Following successful trials, all DS8R’s shipped from our UK factory will now function over an extended output range of 0-1000mA, with increments of 100µA.


New Current Amplitude Limit

Early feedback from existing DS8R users has also prompted the inclusion of some important and sought after feature enhancements. First, we have added a current amplitude limit or lock, which allows the operator to temporarily set the maximum current level to something other than the default 1000mA. This feature is of particular importance to any DS8R users working at the lower end of the current output range, as they understandably want to avoid accidental delivery of excessively high stimuli to their subjects. Using a simple press-and-hold feature added to the amplitude dial, it is now possible for a user to activate and deactivate an output current limit of between 10mA and 999mA.

DS8R Amplitude Limit Digitimer

Re-scaled External Control Input

The current amplitude limit also has benefits for users employing the DS8R’s external analogue voltage Control Input. If an operator sets the output range to 0-10mA using the current amplitude limit, the rear panel Control Input is re-scaled accordingly. This not only makes it impossible for a voltage applied at this input to cause the current to exceed 10mA, but also gives the user finer control over the output amplitude. For example, if the DS8R is set to the default output range of 0-1000mA, voltage signals applied to the rear panel Control Input will be scaled over this range (i.e 0-10V gives 0-1000mA). This means that in order to increase the current by 0.1mA, the input voltage would only need to change by 1mV and such a small change may be masked by noise within the input signal. However, if the DS8R output range is set to 0-10mA, this same 0.1mA change in current can be reproduced by a much larger 100mV change in the input voltage signal. This re-scaling should also help to remove flickering in the current display when the DS8R uses an externally applied voltage level to set amplitude.

“I recently purchased a DS8R with a 2mA minimum current level, can I upgrade?”

Yes, anyone that has purchased a DS8R limited to a minimum current setting of 2mA can take advantage of these enhancements, however, the DS8R would need to be returned to Digitimer for an upgrade to the latest hardware and firmware. This will also give our engineers an opportunity to fully re-test and calibrate the stimulator, ensuring everything is operating within specification before it is returned. If this service is something you would like to arrange or discuss with us, then please get in contact directly or via your supplier/local representative.