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ITC-18: 16-bit data acquisition interface
- All synchronous analog and digital channels are
optically isolated
- Eight simultaneously sampling differential analog
input channels
- Eight 18-bit 200kHz A/D converters
- 200kHz to 12Hz sampling in 1.25µS steps (200kHz max
aggregate)
- Programmable input gain: 1x, 2x, 5x, 10x
- Analog input range: + 10.24Volts
- Four pseudo differential analog output channels
- Four 18-bit instrumentation grade D/A converters
- Analog output range: + 10.24Volts
- Sixteen synchronous digital input channels
- Thirty-two synchronous digital output channels,
fourteen with current sink
- Sixteen asynchronous digital output channels
- Large 1024 kilosample FIFO now included at no
additional cost
- PCI, and USB 2.0 host interfaces available
- Easy installation, no IRQ or DMA channel settings
- Compatible with Windows9x, ME, NT, 2000, XP, MacOS
classic, MacOS X (PPC and intel), LabView for Windows, MatLab and
Linux
ITC-18, the second generation low-noise 16-bit data
acquisition interface from InstruTECH Corporation. The ITC-18 offers unsurpassed capability
while retaining all of the exceptional features of its predecessor, the
ITC-16. The ITC-18 provides a major
improvement in the quality of acquired data, making measurements that would
otherwise not be possible.
Hardware Configuration
The
ITC-18 is an external rack-mountable data acquisition unit that is attached
to the computer using a dedicated host interface. This configuration offers major advantages over traditional
data acquisition designs. One
advantage is noise performance.
Most data acquisition devices are printed circuit boards installed
directly into the computer. The
interior of a computer is an electrically noisy environment that will
dramatically affect the noise performance of high speed D/A and A/D
converters. Mounting all of the
analog electronic components in an external box provides the most effective
means of shielding the analog signal from this noise.
Another advantage is the
capability to use the analog front end (ITC-18 rack unit) with a variety of
host interfaces. Moving the ITC-18
from one computer platform to another is a simple matter of using the
appropriate host interface, and installing compatible software. Utilizing the same hardware when
changing computer platforms provides a cost effective upgrade path to newer
computer technologies without sacrificing your initial investment. Since
the ITC-18’s initial inception we have designed host adapters to interface
to various computer bus architectures (i.e. ISA, NUBUS, PCI, and USB 2.0).
Optical Isolation
The analog
electronics of the ITC-18 are optically isolated from the digital circuitry
of the computer. This provides
complete electrical isolation between the computer and the measuring
equipment. Computers contain
digital electronics that switch at high speed, producing large electrical
transients. The computer ground
functions as the return path for these transients, resulting in substantial
high-frequency ground noise. The
ITC-18 has a completely separate analog ground that is isolated from the
computer ground. With the ITC-18
computer ground noise is not coupled into the measurement.
Optical Isolation is essential
if low-noise analog outputs are desired.
The optical isolation of the ITC-18 brings with it another
benefit that simplifies complex measurement systems. Since the analog
inputs and outputs of the ITC-18 float with respect to power ground, the ITC-18
and the computer are not a source of ground loop problems.
Analog I/O
A unique design
characteristic of the ITC-18 is the synchronization of all analog and
digital signals. All inputs and
outputs are updated simultaneously.
Most data acquisition devices on the market do not do this. They sample multiple channels by using a
multiplexer. This means that there
is a time delay between the samples from each channel. This makes timing correlation
measurements difficult.
The ITC-18 provides
eight analog input channels. Each
input channel uses an 18-bit A/D converter preceded by a programmable gain
stage. Each A/D input can be
programmed with a full scale range of +1, +2, +5, or +10
Volts. This gain stage reduces the need for external signal amplifiers
before the ITC-18. Using separate
A/D converters for each analog input channel also has other
advantages. One benefit gained by
using separate A/D converters is reduced crosstalk between channels. The same multiplexer mentioned in the
previous paragraph, is the source of another disadvantage. It is a single point where all of the
analog input signals connect. This
point, where the analog signals come together, can introduce cross coupling
between the signals. The amount of
crosstalk will vary based on frequency and amplitude. High-frequency signals show the greatest
coupling into other channels while large amplitude signals will also couple
into smaller signals. The ITC-18
has no measurable cross talk between channels.
The ITC-18 provides
four 18-bit instrumentation grade D/A converters featuring high accuracy
with less than 1 bit (~300 µV) of noise. This extremely low noise allows for the
observation of least significant bit transitions. The D/A circuitry used in
the ITC-18 is temperature stabilized and “De-glitched” for ideal
performance. A typical D/A circuit
will have a large glitch energy around zero and major bit transitions, the
ITC-18's D/A converters are free from this artifact.
The ITC-18 uses a
“sequence RAM” to control the sampling order of both the analog and digital
channels. This provides the ability
to update individual channels at different rates. This arrangement optimizes the acquisition of signals with
dissimilar bandwidth.
This architecture
makes the ITC-18 particularly important when making measurements using
high-frequency signal sources, multiple signal sources with large
differences in amplitude between them or when analyzing multiple signals
for timing correlation.
Digital I/O
The ITC-18 provides sixteen digital inputs,
thirty-two digital outputs, seven sequence RAM trigger outputs and fourteen
asynchronous non-isolated digital outputs.
The digital input channels feature level sensitive or latched
modes. For maximum versatility the
inputs can be inverted, allowing rising or falling edge triggering. Thirty-two digital output channels in
two banks of sixteen, with fourteen channels paralleled with current sink
circuitry for driving perfusion valves or other devices directly. Seven programmable trigger outputs for
triggering from any location in the scanning sequence RAM and fourteen
asynchronous auxiliary digital outputs that can be updated at any time
regardless of the ITC-18's acquisition state. ITC-18’s that use a USB-18 host interface have an additional
sixteen asynchronous non-isolated digital inputs and outputs.
FIFO Memory
The ITC-18 is
supplied with a large 1024 kilosample FIFO memory for input and output
data. The ITC-18 allows data
acquisition to be performed independent of the activity of the host
computer. A large FIFO memory
allows uninterrupted continuous hi-speed acquisition with today’s
multitasking operating systems.
Specialized
Applications
The ITC-18 uses programmable
gate arrays that allow the internal hardware to be altered for specialized
applications. One available application is the Artificial Synapse
Dynamic Clamp. The clamped cell
is connected to an A/D input via a Voltage Clamp amplifier. The stimulus is computed, based on
voltage measured from the cell, lookup tables for excitation, inhibition
and conductance values and other parameters. This stimulus is applied to the cell via the current input of
the Voltage Clamp amplifier.
Available Host Interfaces
PCI-18
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The PCI-18
host interface card is a short form factor, 32-bit, 33 MHz 5Volt PCI bus
plug in card. The PCI-18 is
compatible with Apple, PC, and other computer systems that feature a
5Volt PCI Bus. Please note that the
PCI-18 can only be physically connected to a 5Volt or Universal PCI bus
connector.
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PCI-18V3
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The PCI-18V3 host
interface card is a short form factor, 32-bit, 33 MHz 3.3Volt PCI bus
plug in card. The PCI-18V3 is compatible
with Apple G5, PC, and other computer systems that feature a 3.3Volt PCI
Bus. Please note that the
PCI-18V3 can only be physically connected to a 3.3Volt or Universal PCI
bus connector.
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USB-18
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The USB-18 host interface is a USB v2.0 high-speed (480Mbps)
interface for Apple, PC, and other computer systems that feature USB v2.0
high-speed ports.
An extra feature of the USB-18 is the addition of sixteen
asynchronous digital input and output lines.
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Technical Specifications
Analog Input:
Number of channels 8, differential, optically isolated
Type
of
ADC
successive approximation
Input connector BNC
Resolution
18-bit converter,
16-bit data (1 in 65536)
Acquisition rate 200kHz aggregate
Input
range
-10.24 to +10.239Volts
Aperture delay 10 ns
Aperture jitter 50 ps rms
Conversion speed software selectable, 5µS min
Differential nonlinearity +0.002% of FSR
Drift
+50
ppm/ °C
Input impedance 1MΩ
Signal-to-noise ratio +90dB
Crosstalk
<1 LSB
Programmable Gain:
Gain
software selectable, 1, 2, 5,or 10V/V
Settling
time
3.5µS to 0.01% all gains
Nonlinearity
+0.0003%
of FSR
Max. input voltage +40 Volts
Input
CMRR
100dB
Digital Inputs:
Digital
inputs
16, logic level, optically isolated
Input
type
CMOS logic compatible
Operational mode software
selectable,
level sense / latching
active high / active low
Minimum pulse width 150
ns
Input connectors bits
(0 to3) on front panel BNC
16 bits on rear panel connector
Max. input voltage +40
Volts
Trigger Input:
Number
1, hardware selectable
isolated / non-isolated
Input
type
CMOS logic compatible
Operational mode software selectable,
edge mode and invert sense
Minimum pulse width 150 ns
Input connector BNC on front panel
Max. input voltage +40Volts
Analog Output:
Number of channels 4,pseduo-differential,
optically isolated
Type of DAC double
buffered, multiplying
Output connector BNC
Resolution
18-bit converter,
16-bit data (1 in 65536)
Output Range -10.24
to +10.239Volts
Conversion speed software selectable,
5µS max
Gain
error
0.2% of FSR
Gain
linearity
<2dB
Gain
drift
+25
ppm of FSR/ °C
Signal-to-noise ratio 116dB
Output impedance 200Ω(for output
overload protection)
Short circuit to ground indefinite
Output load current +8mA typical
Digital Outputs:
Standard
Number
32, optically isolated
Output driver AC, HCT, ACT, HCT, VCT, or
8 TTL loads
Output connectors bits (0 to 3) on front panel BNC
32 bits on dual 50 pin connector
High current drive
Number
14, optically isolated
Output driver AC, HCT, ACT, HCT, VCT, or
8 TTL loads
Output connector 14 bits on DB-25 pin connector
Output sink current 350mA maximum
Asynchronous outputs
Number
16, non-isolated
Output driver HC logic compatible
Output connector 34 pin connector
Sequencer outputs
Number
7, optically isolated
Output driver AC, HCT, ACT, HCT, VCT, or
8 TTL loads
Output connector 7 bits on dual 50 pin connector
Trigger Output:
Number
1, selectable isolated / non-isolated
Output
driver
AC, HCT, ACT, HCT, VCT, or 8 TTL loads
Output connector BNC on front panel
Max. output current 6mA
Software and Drivers:
* MacOS classic C/C++ Metrowerks libraries
Carbon Driver and Framework library
Wavemetrics IGOR Pro XOP’s
Heka PatchMaster, Pulse,
X-Chart
AxoGraph
InstruTECH AcquireT
PulseControl XOP’s
MacOS
X
(PPC)
Carbon Driver and Framework library
Wavemetrics IGOR Pro Carbon XOP’s
Heka PatchMaster
AxoGraphX
InstruTECH AcquireT
MacOS X (Intel) Framework library
Wavemetrics IGOR Pro Carbon XOP’s
Heka PatchMaster
AxoGraphX
InstruTECH AcquireT
* Windows 9x, ME, NT, 32 bit C/C++ library, DLL and driver
2000, XP, Vista Wavemetrics IGOR Pro XOP’s
National Instruments LabView
Heka PatchMaster, Pulse,
X-Chart, TIDA
InstruTECH AcquireT and Ecell
Strathclyde WinWCP
AxoGraphX
Linux
Driver and C/C++ library
* No longer
supported but still available upon request.
All drivers are available for download.
A note about Macintosh G5 computers
Apple has once again changed the PCI bus on their Power Mac G5
desktop computers. The latest
release, as of November 2005, use’s a PCI Express bus architecture, this is
also true for the Intel based Mac computers. The PCIexpress bus IS NOT compatible with either the PCI-18
or PCI-18V3. For these new systems
the USB-18 host interface is available.
Power Mac G5 computers before November 2005, used a 3.3 Volt
PCI /PCI-X bus architecture. These
systems are compatible with the PCI-18V3 host interface.
FIFO Memory:
Standard:
1024 kilosample FIFO
Model Numbers:
ITC-18/PCI:
ITC-18 with 5Volt PCI bus host interface
ITC-18/PCIV3: ITC-18
with 3.3Volt PCI bus host interface
ITC-18/USB:
ITC-18 with USB 2.0 host interface
OEM version also available. Please contact us with your requirements
Power Requirements:
85-264VAC, 47-440
Hz, 15 Watts
Dimensions:
Width: 19"
Height: 1.75"
Depth: 10.5"
Weight: 8 pounds
Warranty:
Two years parts and labor
Specifications are typical at 25oC
unless otherwise noted.
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