High Power Stimulator Model HP-2a Operator's
Guide
Front Panel Layout and Controls
The TRIGGER MODE Switch determines how and when
each output pulse will be issued. There are three Modes:
1. Free Run: Output pulses are issued continuously.
2. Follow: The Output current will be set to the value
of the Current Adjust pot whenever and for as long as the TRIGGER
Switch is held, or at any time the EXTERNAL TRIGGER Input is above
2V. An externally generated stimulate sequence can be fed to the
HP2 with the desired pulse width, repetition rate, and duration.
10 microseconds is the minimum time recommended between each input
transition.
3. Gated: Pulses are issued as long as the MANUAL TRIGGER
Switch is held, or as long as the EXTERNAL TRIGGER Input is maintained
above 2V. A momentary push or trigger will issue just a Single
Pulse.
The EXTERNAL TRIGGER Input BNC allows remote triggering
of the unit, depending on the MODE Setting (above). A logic Low
Signal is from 0V to +2V, and a High is from +2V to +15V. Damage
will not occur for any signal between 50V and +50V.
The SYNCH OUTPUT BNC will issue a +5V pulse each time an
output pulse of either polarity is issued. The length of this
Synch pulse is identical to the Output Pulse Width.
The PULSE WIDTH Switch determines the length of time (100µS,
500µS, or 1mS) that the output is active during each pulse.
The Rise and Fall times of the Current Output are less than 10µS.
The PULSE PHASE Switch is used to set the output polarity
It can be set to issue only positive pulses, only negative pulses,
or pulses of alternating (positive, then negative) bi-phase polarity.
These pulses are all referenced to chassis ground.
The PPS MULTIPLIER Switch and the PPS RATE ADJUST
Potentiometer together determine how many output pulses are issued
per second. Thus, the PPS rate can be selected in three overlapping
ranges from 1 to 10 (x1 PPS MULT, Pot set from 1 to 10), 5 to
50 (x5 PPS MULT, Pot set from 1 to 10) and 20 to 200 (x20 PPS
MULT, Pot set from 1 to 10)
The CURRENT MULTIPLIER Switch and the CURRENT ADJUST
Potentiometer are similarly configured to provide output currents
from 1 milliamp to 1000 milliamps (1 Amp) in three ranges. The
unit will attempt to put out +/- 60 Volt pulses unless the loading
of the output bath is greater than the Current setpoint. When
this setpoint is reached during each pulse, the output voltage
will be adjusted to maintain that output current.
The MAIN POWER Switch applies the 110VAC line power to
the transformer-isolated internal supplies. The unit is protected
with a 2 Amp fuse at its 110VAC power connector. There is also
a spare fuse inside the fuse holder.
The POWER & PULSES LED Indicator shows Green when the
internal supplies are operating properly. This indicator also
shows Amber each time an output pulse is issued as an easy verification
of unit operation.
The OUTPUT PULSES BNC Connector is the high power output
of the unit. For safety, the outer sleeve of this connector and
the outer ground braid of the co-ax cables you connect to it are
at chassis ground.
The CURRENT MONITOR BNC allows examination of the actual
output current pulses being delivered by the unit. The output
will produce 1mV for each 1mA of output current. Note that
if the output is not connected to a load, this current monitor
will always read Zero.
ELECTRICAL SAFETY NOTE:
The Output's center conductor produces momentary hazardous potentials
above 60 Volts. Care should be taken to avoid coming in contact
with the center conductor when the unit is operating.
REV 8/2001