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1.
What
is the maximum trigger rate of the DS3?
The
unit can be triggered fast enough to allow >99% "on"
time, but the "off" time must >20 microseconds - so,
very fast!
2.
Can
the DS2A or DS3 be used to stimulate human subjects?
No,
neither the DS2A nor the DS3 have medical device directive (MDD)
certification. We offer the MDD compliant DS7A
stimulator for human/patient connection.
3.
Can
I control the DS2A or DS3 using a computer?
Yes
and no. The DS2A and DS3 both feature 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.
4.
I
want to stimulate with a longer pulse duration than 2 seconds, in
order to lesion some tissue, is it possible to do this?
Yes,
there are two simple methods.
(i)
The DS3 and the DS2A MkII both have 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.
5.
I
can't decide between the constant current DS3 and constant voltage
DS2A MkII- how should I choose?
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.
6.
I have an old DS2 constant voltage stimulator and I recall that
Digitimer offer a conversion to constant current. Is this
still possible? 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.
7.
Is it possible to use two DS3 stimulators in parallel in order to
stimulate through the same electrodes with different pulse types? Yes,
this is quite simple to setup and has been summarized in an application
note.
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