Operator's Manual
DS7A - Constant Current Stimulator
Stimulus Control
There are three parameters on the unit that determine the strength and polarity of the stimulus given to the
patient.
These are:-
stimulus duration set by 'Pulse Duration' control
stimulus polarity set by the 'Pulse Polarity' control
the current set by 'Current max.' control and 'x1 / x10' Range Switch
maximum voltage set by 'Volts max.' control
(only has an effect if output is out-of-compliance.)
The rate at which the unit is triggered will also determine the strength of the stimulus given to the patient.
'Pulse Duration' control
This six position switch selects the duration of the stimulation pulse presented to the patient. The settings
between 50 and 500 microseconds are more appropriate for percutaneous stimulation.
'Pulse Polarity' control
The control is a three position left/centre/right toggle switch. Two indicators (Green) show which polarity of
output will be delivered after the next stimulus trigger and one indicator (Amber) warns the operator that
the trigger pulses are too fast.
'Normal' Polarity
'Normal' is defined as the red output socket going positive with respect to the black output socket. This
mode is selected by placing the toggle switch into the left position.
'Reverse' Polarity
'Reverse' is defined as the red output socket going negative with respect to the black output socket. This
mode is selected by placing the toggle switch into the right position.
'Alternating' Polarity
'Alternating' is defined as 'Normal' followed by 'Reverse', repeatedly. This mode is selected by placing the
toggle switch into the centre position.
“Too-fast” Warning and Cut-out
If the trigger signal applied to the DS7A is in excess of 100Hz (10ms repetition), the amber “Too-fast” LED
will illuminate. This LED will stay on for the duration of the excessive trigger rate, and for 1 second
afterwards. This will cause the unit to immediately stop delivering stimuli as well as turning on the Amber
“Fault” LED. When the DS7A has gone into this error state, the Output Enable switch must be moved to
“OFF” (downwards) to reset the DS7A's error logic.
This inhibition of output is only operative in the alternating polarity mode. In the normal and reverse modes
the standard limit of 1000Hz exists, subject to other stimulus parameters.
'Current max.' control and 'x1/x10' Range switch
These two controls set the amount of constant current stimulation given to the patient. The 10-turn rotary
dial goes from '0.00' (zero stimulation) to '9.99' which is either 9.99 milliamps or 99.9 milliamps dependent
on the 'x1/x10' switch. This current is only possible if the voltage available is sufficient to generate the
required current. This is set by:-
Digitimer Ltd.
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Copyright © 2014
File Ref: N:\Docs\Company\Manuals\DS7A\Issue-14\DS7A-iss14.odt
Last Revised: February 1, 2017
