System 3
7-71
PZ3 Low Impedance Amplifier
Clip Warnings
Analog clipping occurs when the input signal is too large. If analog clipping occurs,
TDT recommends switching the PZ3 into high input range mode. For more
information see “Modifying the Input Voltage Range on the PZ3 ” on page 7-71.
While the amplifier is recording, the front panel LEDs can act as clip warning
indicators (according to configuration settings set using the PZ3_Control macro). If
an analog signal approaches the PZ3s clipping range, the PZ3 LEDs for the
corresponding channel are lit red.
Note:
The LED Indicators are also mirrored on the RZ2 LCD display.
When recording, the status LED located below the Display Mode button indicates the
status of the Clip Indicators. Solid green indicates that clip warning is disabled and
orange indicates the clip warning is enabled.
To enable clip warning, press the
Display Mode
button on the PZ3 front panel.
Alternatively the PZ3_Control macro can be used to enable or disable the clip
warning indicators. For more information on the PZ3_Control macro see“PZ3 Software
External Ground
The external ground is optional and should only be used in cases where the subject
must occasionally make contact with a metal surface that isn’t tied to the animal
ground, such as a lever press. When contact is made, a ground loop is formed that
temporarily adds extra noise to the system. Grounding this metal surface directly to
the TDT hardware removes this ground loop at the cost of raising the overall noise
floor a small amount.
A banana jack located on the back of the PZ3 (directly to the right of the charger
input) provides connections to common ground for the first bank of channels (1-
16). A cable kit is also provided to ensure cables used with the external ground are
suitable for this use. Each kit includes: one male banana plug to male banana plug
pass through and one male banana plug to alligator clip pass through. These cables
also include ferrite beads to remove any potential RF noise that might travel through
the cable. For best results position the ferrite bead close to the source of the RF
noise.
Modifying the Input Voltage Range on the PZ3
In the default mode, the PZ3 has an effective differential input range of +/- 3mV,
which TDT recommends for EEG, LFP, and ECOG. If recordings demand a higher
input range such as EMGs, the alternate High Input Range mode allows the input
range to increase to +/- 20 mV.
Important!
The PZ3 automatically detects the gain setting and voltage range and scales the
signal output accordingly.
Note:
The signal to noise performance is better while operating in the +/- 3mV input
range.
