 Multi-cage / multi-channel EEG, EMG and
activity monitor
ActiveRat
is an elegant solution for collecting multi-channel EEG, EMG and activity
(infrared detector) data
from multiple freely-moving small animals. The system architecture
incorporates amplification and 24-bit analog-to-digital conversion in a
single, compact unit located inside or immediately adjacent to the animal
housing. Up to 32 A/D boxes are synchronized but remain galvanically
isolated from each other by means of a fiber-optic data daisy chain.
Systems with more than 32 A/D boxes connected to a single host PC are also
possible on a custom basis, with a proportional reduction in channels per
cage and/or sample rate. |
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|
The fiber-optic daisy chain
permits many meters distance between cages and between the last A/D box and
the data acquisition PC (user-supplied), where data from all animals are
displayed and stored. Each A/D box has an integrated low-capacitance
DC-DC converter. So, all A/D boxes can be powered from a single un-isolated
power supply. The galvanic isolation of each separate animal is still
ensured by the internal DC-DC converter. The 2 input channels for IR
detectors and extra logic input for a timing switch are coupled to the ADC
circuitry via integrated low-capacitance optocoupler ensuring the galvanic
isolation of each animal.
The
RatView data acquisition software provided with the system manages the
complex task of storing long-term records from multiple animals. The
RatView software is a LabVIEW application, and it is provided as an
executable that requires only the free LabVIEW runtime engine (provided) to
operate. You do not need to have a LabVIEW programmer to operate the
system. However, RatView is open-source software, meaning that the
LabVIEW virtual instrument source code is provide with the system, and users
are free to modify it to suit their own needs. A typical RatView
software configuration will handle a total of 32*16+1=513 channels (last channel is sync
channel). The switch data and the CMS in range data are encoded in the LSBs
of channel 15 and 16 of each cage, so no channels are wasted for these extra
bits.
Features
- 16 monopolar channels (referencing in software, for
example to 7 differential leads)
- 24-bit A/D per channel, simultaneously sampled
- +-262 mV input range
- 2048 Hz maximum sample rate
- USB 2.0 interface to a single Windows XP SP2 host PC
(user-provided)
- Remote acquisition review and control of acquisition
via TCP/IP link
- Up to 32 cages per daisy chain. Systems with more
cages are possible, and have been supplied on a custom basis. The
maximum throughput total is 1 MSample/s, which is equivalent to 32
cages * 16 channels/cage * 2048 Sample/s or 64 cages *
16 channels/cage * 1024 Sample/s. Please inquire for more
details.
A/D box Controls, Inputs, Outputs and Indicators
 Front panel:
- 25-pole DIN input connector to rotor: channels 1-14,
CMS, DRL, 5VDC
- 4 LED indicators: power (green), CMS in range (blue),
sync (green), trigger (red)
- 5 pole DIN connector: PIR channel 1, PIR channel 2,
ground, 5 VDC, trigger
Rear panel:
- Optic fiber input and optic fiber output
- Control to set the cage number (two digit up/down
controls with number indication)
- Power Input: 13-15 VDC, 200 mA per AD-box
Infrared motion detector signals are handled by channel 15
and 16, so channels 1-14 remain available for animal electrodes. The
Trigger input can be used for an external switch. This switch can be used to
add timing pulses to the EDF/BDF file (extra channel added in software).
Additional Notes
-
 ActiveRat supports up to 7 differential EEG / EMG leads per
animal.
- The minimal ActiveRat system configuration incorporates
8 A/D boxes with 16 channels each.
- PIR are channels for infrared motion detectors used in
most labs to log activity of the animals. The PIR detectors are mains
powered. Therefore, the two PIR inputs are coupled to the the amplifier
via analog optocouplers.
- The trigger switch (to log injection time of medicines)
is also coupled via an optocoupler.
- Power input is coupled to amplifier/ADC circuitry via a
DC-DC converter. Electrode inputs are galvanically floating
(isolated from power input, and from PIR/Switch inputs).
- AD-box can interface directly with (implanted) passive
electrodes (user-supplied). Alternatively, a miniature preamp can be used
in the cable from rat to rotor.
- Video monitoring is currently not implemented.
ActiveRat Specifications
|
Sample-rate per channel: |
2048 Hz (lower sample
rates possible on a custom basis) |
| Max.
number of channels @ selected sample rate: |
512 |
| Bandwidth
(-3dB): |
DC - 400 Hz |
| Low-pass
response |
5th order sinc
digital filter |
| High-pass
response |
fully DC coupled |
| Digitization: |
24 bit, 4th
order Delta-Sigma modulator with 64x over sampling, one converter per channel |
| Sampling
skew: |
< 10 ps |
| Absolute
sample rate accuracy (over temp range: 0-70 C) |
0.1 Hz |
| Relative
sample rate accuracy (jitter) |
< 200 ps |
| Quantization-resolution |
LSB = 31.25 nV,
guaranteed no missing codes |
| Gain
accuracy: |
1 % |
| Anti
aliasing filter |
fixed first order analog
filter, -3dB at 3.6 kHz |
| Total
input noise (Ze < 10 kOhm):, full bandwidth |
0.8 uVRMS (5 uVpk-pk) |
| 1/f noise
(Ze < 1 MOhm): |
1 uVpk-pk @
0.1..10Hz |
| Amplifier
current noise: |
< 30 fArms |
| Input
bias current: |
< 1 nA per channel |
| Input
impedance |
300 MOhm @ 50 Hz (1012
Ohm // 11 pF) |
| DC
offset: |
< 0.5 mV |
| DC drift |
< 0.5 uV per degree
Celsius |
| Input
range |
+262 mV to -262 mV |
| Distortion |
< 0.1 % |
| Channel
separation |
> 100 dB |
| Common
Mode Rejection Ratio |
> 80 dB @ 50 Hz |
| Isolation
Mode Rejection Ratio |
> 160 dB @ 50 Hz |
| Power
Consumption |
2.5 Watt per AD-box with 16 channels (12.5 VDC, 200 mA) |
| Leakage
current, normal operation: |
< 1 uA rms. |
| Leakage
current, single fault |
< 50 uArms |
| Trigger
inputs: |
1 input on A/D box, TTL level |
| PC
interface: |
USB 2.0 |
| Size of
A/D box (H x W x D) |
190*140*46 mm |
| Weight of
A/D box |
< 0.5 kg |
| Warranty |
3 years |
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