Operator's Manual
DS7A - Constant Current Stimulator
Maximum Stimulus Repetition Rates
Note that frequencies above 100Hz (10ms repetition) are not possible in the Alternating
polarity mode.
The DS7A has internal fuses that limit the amount of power that is supplied to the patient. This results in a
restriction on the stimulus Repetition Rate - vs - Pulse Duration - vs - Stimulus Intensity which is shown on
the graph on the following page .
This graph shows that, for instance, with 2 ms pulse duration any stimulation current up to the maximum of
100 mA can be delivered for a repetition rate less than approximately 25 per second.
The Maximum frequency at which the unit can be triggered for a given output current and pulse duration
can be calculated using the following equation.
Freq. < 5,000,000 / (PW x I
max
)
where
Freq.
is the trigger frequency, in pulses per second (Hz)
PW
is the Pulse Duration set on the unit, in microseconds (µs)
I
max
is the stimulus current, in milliamps (mA)
In most cases of patient stimulation this graph will not be of concern but when the DS7A is used with certain
preparations it may have to be referred to.
Trigger Out Pulse Duration
The Trigger Output Pulse Duration is 1 ms (950±50µs). This limits the minimum interval between any two
stimuli pulses to 1 ms (equivalent to a 1 kHz repetition rate). See section on Trigger Polarity.
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Copyright © 2014
File Ref: N:\Docs\Company\Manuals\DS7A\Issue-14\DS7A-iss14.odt
Last Revised: February 1, 2017
