TDT RA16PA Application guide

RA16PA/RA4PA Medusa PreAmps
Hardware Reference
Updated 2022-10-31

© 2016-2022 Tucker-Davis Technologies, Inc. (TDT). All rights reserved.
Tucker-Davis Technologies
11930 Research Circle
Alachua, FL 32615 USA
Phone: [phone]
Fax: [phone]
Notices
The information contained in this document is provided "as is," and is subject to being changed,
without notice. TDT shall not be liable for errors or damages in connection with the furnishing, use, or
performance of this document or of any information contained herein.
The latest versions of TDT documents are always online at https://www.tdt.com/docs/
RA16PA/RA4PA Medusa PreAmps | 2

Table of Contents
RA16PA/RA4PA Medusa PreAmps
4Medusa Overview
5Medusa Features
5Analog Acquisition Channels
5Clip Warning Lights
5Power Light
6Headstage Connector
6Base Station Connector - To Base
7Power
7LEDs
7Power Requirements
8RA16PA/RA4PA Technical Specications
8Pinout Diagrams
Table of Contents | 3

RA16PA/RA4PA Medusa PreAmps
Medusa Overview
The Medusa Preampliers are low noise digital bioampliers and are available with either PCM
or Sigma-Delta ADCs. The system amplies and digitizes up to 16-channels of analog signal at
a 24.414 kHz sampling rate. The amplied digital signal is sent to the base station via a
noiseless ber optic connector.
Digitizes either four or 16 channels at acquisition rates of approximately 6, 12, or 25 kHz.
Connects to the headstage via a DB25 connector.
Powered by a Lithium-ion battery that provides 20 hours of continuous data acquisition in
16-channel mode and 30 hours of operation in 4-channel mode.
Clip warning lights indicate when any signal is -3 dB from the preamplier's maximum
voltage input.
•
•
•
•
RA16PA/RA4PA Medusa PreAmps | 4

Medusa Features
Analog Acquisition Channels
The RA16PA and RA4PA standard Medusa Preampliers acquire signals using 16-bit PCM
ADCs, which provide quality acquisition with minimal delay. The RA16SD and RA4SD use
Sigma-Delta ADCs, which have several characteristics that improve signal quality.
Oversampling of the signal before conversion removes aliasing of high frequency RF signals.
RA16SD testing indicates that signals greater than 150% of the Nyquist frequency are removed
from the signal. This allows users to acquire at lower sampling rates (6 kHz) without worry of
signicant aliasing. In addition, each converter also has a two pole anti-aliasing lter (12 dB
per Octave) at 7.5 kHz. However, the sigma-delta ADC's have a xed group delay of 20 samples
(compared to four samples for the RA16PA). When using the RA16SD this group delay must be
taken into account when the data is displayed or acquired (for example, adding a SampDelay to
the RPvdsEx circuit).
Clip Warning Lights
When the input to a channel is greater than -3 db from the preamplier's maximum voltage
input, a light on the top of the amplier is illuminated. The rst column of lights corresponds to
channels 1-8 and the second column corresponds to channels 9-16. The clip warning light
indicator can be turned off by ipping a switch on the end of the amplier.
Power Light
The power light is in the top corner of the amplier. It is illuminated when the device is on. It
ashes quickly if the battery is low. It ashes slowly while the battery is charging. Note: The
ashing LED indicator is only available when the amplier is powered on and connected to a
powered base station.
RA16PA/RA4PA Medusa PreAmps | 5

Headstage Connector
The headstage connector is a 25-pin (16-channel) connector. Information on the pin inputs is
provided with the technical specications.
Base Station Connector - To Base
Use the provided ber optic pair (white connectors) to connect the To Base port on the
preamplier to the optical input port on the base station.
The duplex ber optic cable has identical one-piece connectors at each end. There is a V-
shaped groove on one side of the connector and a raised rectangle on the other. As shown in
the image above, plug the connector into the RZ6 port with the raised rectangle side up. Plug
the connector into the preamplier with the V-shaped groove up.
RA16PA/RA4PA Medusa PreAmps | 6

Medusa PreAmp Connection Diagram
Power
A switch on the back powers up the amplier. The ber connector at the right will be
illuminated when the amplier is on.
LEDs
This switch turns the clip warning lights on top of the amplier on or off.
Power Requirements
The Lithium-ion batteries charge in four hours. Keeping the battery charger connected to the
amplier does not affect the battery life. However, the charger will signicantly increase the
noise of the system if it is plugged in while an experiment is running. A 6 volt battery charger is
included with the amplier. The charger tip is center negative. If it is necessary to replace the
charger make sure that the power supply has the correct polarity.
The Li-ion battery supplied with the system cannot be removed. If battery life longer than 30
hours is required, an external battery pack can be connected to the voltage inputs of the
charger. TDT recommends a 6 Volt (minimum) to 9 Volt (maximum) battery, such as lead acid
batteries used for motorized wheel chairs. See Tech Note #0256 for more information.
RA16PA/RA4PA Medusa PreAmps | 7

RA16PA/RA4PA Technical Specications
Includes specications for the RA4PA, RA16PA, and RA16SD Medusa Preampliers.
Pinout Diagrams
16- and 4-channel pinouts (all models built after 2002):
A/D RA4PA: 4-channels 16-bit PCM
RA16PA: 16-channels 16-bit PCM
RA16SD: 16-channels 16-bit sigma-delta
Sample Rate 6, 12, or 25 kHz
Maximum Voltage In RA4PA and RA16PA: ±4 mV
RA16SD: ±5 mV
Frequency Response 3 dB 2.2 Hz - 7.5 kHz
Highpass Filter 2.2 Hz
Anti-Aliasing Filtering RA4PA and RA16PA: 7.5 kHz (3 dB corner, 1 order, 6 dB per octave)
RA16SD: 7.5 kHz (3 dB corner, 2 order, 12 dB per octave)
S/N (typical) RA4PA and RA16PA: 60 dB
Input Referred Noise rms 3 uV bandwidth 300 - 3000 Hz
6 uV bandwidth 30 - 5000 Hz
Group Sample Delay RA4PA and RA16PA: NA
RA16SD: 20 Samples
Input Impedance 100 kOhms
Power Requirements 500 mA while charging, 60 mA once charged
Battery Li-ion Battery 1950 mAh, 20-25 hour runtime
1000 cycles of charging, not removable by user
Charger 6-9 V DC, >500 mA, center negative
Fiber Optic Cable 5 m standard, maximum cable length 12 m
st
nd
RA16PA/RA4PA Medusa PreAmps | 8

Pin Name Description Pin Name Description
1 A1 Analog Input Channels 14 V+ Positive Voltage (+1.4 V)
2 A2 15 GND Ground
3 A3 16 GND Ground
4 A4 17 V- Negative Voltage (-1.4 V)
5 Ref Reference 18 HSD Headstage Detect
6 DNC Do Not Connect 19 HSD
7 A5 Analog Input Channels 20 A6 Analog Input Channels
8 A7 21 A8
9 A9 22 A10
10 A11 23 A12
11 A13 24 A14
12 A15 25 A16
13 DNC Do Not Connect
RA16PA/RA4PA Medusa PreAmps | 9