TDT RZ2 Manual page 477

Low Impedance Headstages
RA4LI ‐ Four Channel Headstage
The RA4LI headstage is designed for low impedance electrodes with input impedance
between <1 kOhm and 20 kOhm. Electrode connectors are standard 1.5 mm safety
connectors making it easy to connect to standard needle and surface electrodes for
recording evoked potentials and EEG's. The headstage connects directly to the
RA4PA Medusa preamplifier's 25-pin connector. A built in impedance checker can be
used to test each channel and the reference. Additional 20x gain on the headstage
improves signal-to-noise of low voltage signals.
Impedance Checking with the Low‐Impedance Headstage
The Impedance checker on the RA4LI provides a simple check of the channel
impedance relative to ground. To check the impedance level, press the button next
to the channel indicator. The highest-level light indicates the maximum impedance
between the channel and the ground. If all impedance lights are illuminated it is
likely that one of the channels is not properly connected. The (-) impedance button
checks the impedance between the reference and the ground.
PreAmp
Connector
Headstage Voltage Range
When using a TDT preamplifier the voltage input range of the preamplifier is
typically lower than the headstage and must be considered the effective range
of the system. Check the specifications of your amplifier for voltage range. Also
keep in mind that the range of the headstage varies depending on the power supply
provided by the preamplifier. TDT preamplifiers supply +/- 1.5 V, but third party
preamplifiers may vary. TDT recommends using preamplifiers which deliver +/- 2.5
V or less. Check the preamplifier voltage input and power supply specifications and
headstage gain to determine the voltage range of the system.
11-3
Ground
Reference
Low Impedance Headstages