DP-304A, Rev. 091615
Warner Instruments
A Harvard Apparatus Company
8
output will return to baseline in the presence of a constant potential difference at the
headstage inputs.
The amplifier is placed in AC mode by selecting a cut off frequency other than DC (e.g., 0.1,
1.0, 10, 100, or 300 Hz)using the HIGH PASS FILTER control. AC mode is useful for recording
biopotential signals such as EEG, EMG, and ECG.
DC mode
In DC mode, the internal amplifiers are direct coupled (DC coupled). As a result, a
constant potential difference at the headstage inputs will be passed to the amplifier output.
DC mode is useful for making measurements through high impedance fluid filled
microelectrodes. Warner Instruments manufactures a complete line of microelectrode holders
useful in connecting microelectrodes to the DP-304A inputs.
The following electrode holders are recommended for use with DP-304A:
Holder Model Order #
for 1.0 mm OD glass E45P-F10NH 64-1023
for 1.2 mm OD glass E45P-F12NH 64-1024
for 1.5 mm OD glass E45P-F15NH 64-1025
for 2.0 mm OD glass E45P-F20NH 64-1026
Input Connections
The BNC’s on the front panel represent the positive and negative inputs of a differential
amplifier and the outer shell of these BNC’s are connected to the system ground.
For differential recordings, use both the (+) and (-) inputs and one or both of the BNC outer
shells for ground. Set the input toggle switch to the DIFF position.
For single-ended recordings, use the (+) input and one of the BNC outer shells for ground.
Set the input toggle switch to the center position, this automatically grounds the (-) input,
leaving the (-) input BNC open.
Output Connection
The OUTPUT BNC connector on the front panel is the output of the amplifier. It is used to tie
the DP-304A to an oscilloscope or recording device. If a data acquisition system is used, it must
be capable of resolving a ± 10 V signal.
When the OUTPUT BNC of the DP-304A is connected to an oscilloscope (or recording device), the
ground of the oscilloscope will be carried through to the input via the common ground.
Consequently, any part of the experiment that is tied also to the input ground will be
connected to the oscilloscope ground.
NOTE: Under these conditions, any additional grounds connected to the input will
create a ground loop in the system.
