put to provide data
streams that are matched in time for
field or laboratory use.
The 38 segment clock-time conversion
of the Delta-Sigma A/Ds is offset in soft-
ware to provide this time correlated
data. The rugged small module is self-
powered via the USB connection to a PC
laptop. BNC connections are provided
for all I/O signals for secure and easy-
to-use operation.
Type: Noise and Vibration Analysis
DT9837
BUS: USB
DT9837
High Performance USB Module for
Sound & Vibration Analysis
4 simultaneous, 24-bit Delta-Sigma A/D
channels
for high resolution measurements.
Support for four IEPE inputs,
including 4mA
current source.
Portable operation.
No external power supply
needed. Runs on USB power.
Tachometer input support
in the A/D data
stream for synchronizing measurements.
Sampling rate of over 52kHz
to meet your
application need.
Low frequency measurements
supported with a
wide pass band of 0.5Hz to 25.8kHz (0.49 x sam-
pling frequency).
Analog input ranges of +/-10V and +/-1V
with
software-selectable gains of 1 and 10.
One 24-bit Delta-Sigma D/A converter
with
single-value or ultra-smooth waveform capability.
Programmable triggers for analog input
operations
for maximum flexibility. Choose a
software trigger, TTL trigger, or analog threshold
trigger.
Figure 1. The DT9837 has 4 simultaneous IEPE
sensor inputs plus a synchronous tachometer input
and is ideal for portable noise and vibration mea-
surement applications.
DT9837 Features
Summary of Features
A/D Throughput
D/A
Tachometer
Simultaneous
Applications
Per Channel
Channels
Input
Subsystem
Operation
DT9837
52.734kHz
1 Waveform
1 Synchronous
Yes
Vibration,
4 IEPE Inputs
or
to Analog
Acoustics,
Simultaneous Single Value
Data Stream
Sonar
24-Bit
A/D
4mA
+18 V
1M
x1 / 10
1M
x1 / 10
1M
Control
Logic
Programmable
Clock
USB 2.0
High-Speed
D/A FIFO
24-Bit D/A
10kHz
Filter
1 M
x1 / 10
24-Bit
A/D
24-Bit
A/D
24-Bit
A/D
x1 / 10
USB
2.0
4mA
4mA
4mA
A/D 0
D/A Output
External Trigger
Status
A
A
A
A
A/D 1
A/D 2
A/D 3
Tachometer
Input
Compliance Voltage
Figure 2. The DT9837 is a
high performance, multifunc-
tion data acquisition module
for USB that provides A/Ds
with IEPE capability, one
waveform D/A, a tachometer
input, and simultaneous
operation of all subsystems.
Software selectable
AC or DC coupling.
Supported by all DT-Open Layers for .NET
Class Library
compliant software to meet
any application need. WWW
.
DATATRANSLATION
.
COM
US & C
ANADA
(800) 525-8528
G
ERMANY
(49) 7142 95310
UK (44) 1256 333330
2
Figure 3. An OEM, board-level version of the DT9837 is available (DT9837-OEM). The DT9837 and the
DT9837-OEM provide BNC connectors for easy signal connections.
Figure 4. The DT9837 board is encased in a rugged, metal enclosure to ensure CE-compliance and maintain
signal integrity.
4 Analog Inputs with
BNC Connections
Exploded View
4, 24-Bit Sigma-Delta A/Ds with IEPE Conditioning
Powered on High-Speed USB 2..0
Status light
24-Bit
Analog
Signal
Output
External
Trigger
Board Dimensions:
146mm x 100mm
Top Panel
Marked for easy signal connection
DT9837 Board
CE-Compliant Enclosure
Maintains signal integrity
1 Tachometer Input Channel Analog Inputs
The DT9837 module supports four ana-
log input channels and a tachometer
input. Gains of 1 and 10 are supported
for effective input ranges of +/- 10V and
+ /- 1V. The module uses 24-bit Delta-
Sigma analog-to-digital converters
(ADCs) that provide anti-aliasing filters
based on the clock rate. These filters
eliminate aliasing, which is a condition
where high frequency input components
erroneously appear as lower frequencies
after sampling.
You can read data from one or more
analog input channels using an analog
input channel list. You can enter up to
5 entries in the channel list, including
four analog input channels and the
tachometer input.
Analog Inputs with IEPE Functions
Applications requiring accelerometers,
vibration, noise, and sonar measure-
ments often use IEPE sensors. The
DT9837 module supports the following
software programmable IEPE functions
for each of its four analog inputs:
Current source - Enable or disable
the use of a 4mA current source to
drive the IEPE sensors.
AC/DC coupling - Select whether AC
coupling or DC coupling is used.
Delta-Sigma A/D Converters
These modules have built-in anti-alias-
ing filters for superior AC performance
in noise and vibration testing applica-
tions.
Internally, the DT9837 module uses a
Delta-Sigma converter for each analog
input. Delta-Sigma converters offer the
following advantages for analog input
operations, making them ideal for noise
and vibration testing applications.
Reduce noise and improve accuracy
by oversampling each input.
Eliminate errors that result from
aliasing and high frequency noise.
Provide excellent low-level signal-to-
noise performance, which improves
dynamic accuracy on low-level sig-
nals.
Provide excellent differential linearity,
which ensures consistently accurate
data conversion across the full input
range.
Group Delay and Data
Synchronization
Because of the inherent filtering algo-
rithms, Delta-Sigma converters have an
initial delay of 38 clock pulses after the
sample clock is first started and before
the first conversion is completed, due to
the group delay of converters.
The tachometer data (which does not
have the 38 sample group delay) is syn-
chronized with the analog data stream.
This is done through the firmware and
device driver by caching the tachometer
data and aligning it in time with the
analog data in the users data buffers.
Tachometer Input
The DT9837 includes support for a
tachometer input in the analog input
data stream for synchronous measure-
ments. The measurement edge for the
tachometer input is rising. The module
accepts one ±30V, 31-bit tachometer
input signal with a maximum frequency
of 380kHz and a minimum pulse width
of 1.3 microseconds. The threshold volt-
age is fixed at ±2V with 0.5V of hystere-
sis. Measurements are based on two
consecutive rising edges of the tachome-
ter input signals.
The tachometer input is treated like
any other channel in the analog input
channel list; therefore, all the clocking,
triggering, and conversion modes sup-
ported for analog input channels are
supported for the tachometer input.
Waveform Quality Analog Output
The DT9837 supports one 24-bit D/A
converter with an output range of
+/- 10V. You can output a single value
from the analog output channel, or you
can use a software trigger to start a
waveform operation. A two-pole,
10kHz Butterworth filter is applied to
remove clocking noise and smooth sig-
nal output.
A standard waveform such as a sine,
triangle, or square wave is easily pro-
duced by loading the onboard FIFO with
8,192 samples. The specific waveform is
output at a fixed rate of 46.875 kHz.
Great care has been used in design to
minimize the glitch energy for any major
or minor carry. This results in extreme-
ly smooth waveforms.
You can update the analog output
channel as you are acquiring analog
input data for gap-free simultaneous
stimulus and response. Note that since
the module uses a Delta-Sigma D/A
converter, 34 clock pulses are required
before the first D/A conversion is com-
plete.
Analog In
Analog In
Simultaneous A/D
Up to 52.734 kHz per Channel
4 Delta-Sigma
Converters
24-bit
A/D
24-bit
A/D
Tachometer
Input
Figure 5. Simultaneous Delta-
Sigma A/D converters and the
tachometer input are synchronized
through software to accommodate
for the group delay of the A/D
converters.
Wide Band Pass
0.5Hz
25.8kHz
-3dB@
.
49 x Sampling
Frequency
(Eliminate
Nyquist Aliases)
FREQUENCY
- 3dB
0dB
AMPLITUDE
- 3dB single pole
- 6dB per octave rolloff
Near 0 Ripple in Pass Band
(Linear Phase)
-100dB @.55 x
Sampling
Frequency
Built-In Digital
Filter Provides
“Brick Wall”
Roll Off
Figure 6. DT9837 provides software selectable AC and DC coupling. When
AC coupling is selected, the DT9837 provides zero ripple in the wide pass
band and excellent brick wall anti-alias filter eliminates unwanted
high frequency interference. WWW
.
DATATRANSLATION
.
COM
US & C
ANADA
(800) 525-8528
G
ERMANY
(49) 7142 95310
UK (44) 1256 333330
4
Mulitple Module Synchronization for
High Channel Count Applications
The internal clock on the DT9837 module,
which is derived from the USB clock, pro-
vides the timing for both the analog input
and analog output subsystems on the
module. You can synchronize the start of
acquisition on multiple modules by con-
necting all modules to a shared external
trigger input (Figure 7). When triggered,
the modules remain locked to within one
A/D conversion of the clock.
There are five trigger options when using
multiple modules:
Single module
Digital trigger
Analog threshold trigger
Software trigger
Multiple modules
Digital trigger
Software trigger
(uses one DAC output)
Synchronous Operation
The DT9837 supports synchronous ana-
log input, tachometer input, and analog
output operations. Data is streamed
synchronously to host memory. The
synchronous operation allows all I/O
data to be processed and correlated for
all inputs and outputs. This is very
valuable in determining the response
across a device-under-test (DUT) to
stimuli at the same exact instant.
Programmable Triggers
You can start an analog input operation
using either a software trigger, external
TTL trigger, or analog threshold trigger.
Analog output operations start using a
software trigger only. Using the internal
trigger, I/O operations start based on a
software command. Using an external
trigger, analog input operations start
when the module detects a low-to-high
transition on the EXT TRIG (TTL) input
of the module. Using an analog thresh-
old trigger, analog input operations start
when the module detects a signal on
analog input channel 0 that rises above
1.0V.
Programmable A/D Clock
Th