VT1413C - VTI Instruments
64-channel Scanning A/D Converter
Comprehensive Signal Conditioning
On Board
Flexible Scanning/Auto Sequencing
High-speed Data Transfers into
On-board Data Reduction and hi/low
Limit Checking
Signal Digitizing to 100 kHz
Sampling Rate ( * )
The VT1413C 64-channel Scanning A/D is a C-size, single slot,
register-based VXI module. It is designed for high-performance
data acquisition and computer-aided test applications. The key
requirements of these applications are high-speed scanning, 16-bit
resolution, high accuracy (0.01% of reading), 4 mV to 16 V fullscale input (60 V with VXI Technology VT1513A attenuator SCP),
64 kSample dual-ported FIFO buffer for fast data transfers, current
value table for online monitoring, and automatic self-calibration.
The available ranges are determined by the SCP used. An SCP is
required for every input. Each SCP normally supplies input signal
conditioning for eight (8) channels. See the individual SCP Data
Sheet for more information.
The unique design of the analog subsystem provides a new level of
density by combining a 16-bit A/D with a 64-channel differential FET
multiplexer. Up to eight Signal Conditioning Plug-ons (SCPs), most
with eight channels each, can be added to the VT1413C to provide
additional capabilities (i.e., direct input, 10 Hz low-pass filtering,
fixed gain/filter per channel, etc.).
Refer to the VXI Technology Website for instrument driver
availability and downloading instructions, as well as for recent
product updates, if applicable.
Multifunctional Measurement Capability
This module provides multifunction measurement capability within
individual scans without any configuration re-programming. These
include dc voltage, temperature, resistance, and strain.
Comprehensive Signal Conditioning On Board
A full range of signal conditioning is provided by optional Signal
Conditioning Plug-on daughter boards (SCPs) that mount inside
the VT1413C. Most SCPs buffer the signal to be measured and filter
or amplify it before presenting it to the VT1413C’s FET multiplexer
and A/D converter. Other available SCPs provide more advanced
functions such as sample-and-hold and strain bridge excitation and
The SCPs supported by the VT1413C are:
(* 100 kSa/s maximum sampling/scanning rate divided by the
number of channels in the scan list, which can be 1 to 64. )
Model No.
8-channel Direct Input SCP
8-channel 7 Hz Low-pass Filter SCP
8-channel Programmable Filter and
Gain SCP
8-channel Current Source SCP
8-channel 120 Ω Strain Completion &
Excitation SCP
8-channel 350 Ω Strain Completion &
Excitation SCP
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949 • 955 • 1VXI
64-channel Scanning A/D Converter
Model No.
8-channel x16 Gain & 7 Hz Low-Pass Fixed
Filter SCP
8-channel x64 Gain & 7 Hz Low-Pass Fixed
Filter SCP
4-channel Sample & Hold Input SCP
4-channel Transient Strain SCP
8-channel 25 Low-Pass Hz Fixed Filter SCP
8-channel Divide-by-16 Fixed Attenuator &
7 Hz Low-pass Filter SCP
4-wire Resistance Measurement SCP
channel number of any out-of-limit reading since the last INIT
command. The FIFO buffer can then be read to determine the
actual out-of-limit readings.
Signal Digitizing
Refer to the information on each individual SCP for more
The VT1413C is suitable for digitizing of multichannel
transient signals up to a 1 kHz sampling rate when used with
the VT1510A 4-channel Sample & Hold Input SCP anti-aliasing
filters. Digitizing higher frequency signals using the VT1501A
8-channel Direct Input SCP will require the use of external
anti-aliasing filters. The scan trigger, either internally or
externally generated, is used to initiate the channel samples
controlled by the internal sample timer. The typical scan
trigger jitter time is ±100 ps.
Flexible Scanning/Auto Sequencing
Signal Conditioning Plug-ons
Measurement scans can be made in any channel order using
any function on any channel, all at full speed, including autoranging. Up to four unique scan lists, each with up to 1,024
channel entries, can be stored in RAM and selected on the fly
with a single software command. In addition, these scan lists
can be automatically sequenced with a unique auto sequencing
scan list. Lists can be sequenced so as to simplify the scanning
of channels at different rates.
A Signal Conditioning Plug-on (SCP) is a small daughter
board that mounts on VXI Technology’s VXI scanning
measurement and control modules. These SCPs provide a
number of input and output functions. Several include gain
and filtered analog inputs for measuring electrical and sensorbased signals. Refer to the information on each individual
SCP for more details.
Other Features
High-speed Data Transfers into Controller
Data transfer speed has been greatly improved because
multiple VT1413Cs can scan in parallel at full speed and then
sequentially transfer data over the VXI backplane in D16 or
D32 format at rates that match even the fastest embedded VXI
computer. The data is transferred in computer-ready, IEEE-754,
32-bit floating-point real engineering unit format. Two on-board
DSPs facilitate overall performance. The FIFO RAM is a dualported high-speed buffer that stores up to 64,000 samples until
the controller is ready for efficient fast data transfer. For online
monitoring, the Current Value Table RAM contains the most
recently measured values for each channel in use. The CVT and
FIFO RAMs can be accessed asynchronously.
On-board Data Reduction and Hi/Low Limit Checking
Averaging can be enabled on a scan basis to provide averaging
for each channel over two to 256 samples in binary steps. The
averaged data goes to both the CVT and the FIFO buffer. The
maximum sample rate is 1.5 kSa/s per channel for 64 channels,
although higher rates are possible with fewer channels. When
averaging multiple channels in a scan list, scan list switching
and auto-ranging are not allowed. This would distort the
average. Individual high and low limits per channel can be
downloaded to the VT1413C in engineering units format. If
a limit is exceeded, an interrupt or trigger line can be pulled
and the limit register can be read to determine the out-of-limit
channel. A cumulative mode can be selected that holds the
Voltage Measurements
Use any of the following SCPs with the VT1413C to make
voltage measurements: VT1501A, VT1502A, VT1503A,
VT1508A, VT1509A, VT1512A, or VT1513A.
Temperature Measurements
Any of the input SCPs can be used to make temperature
measurements with thermocouples, thermistors, or RTDs,
but the VT1503A, VT1508A, VT1509A SCPs provide higher
accuracy with thermocouples.
Resistance Measurements
Resistance is measured using the VT1505A 8-channel
Current Source SCP and an input SCP or the VT1518A 4-wire
Resistance Measurement SCP. Measurements are made by
applying a dc current to the unknown and measuring the
voltage drop across the unknown. The current source is
provided through the VT1505A.
Static Strain Measurements
The VT1506A and VT1507A SCPs provide a convenient way
to measure a few channels of static strain. When using the
VT1506A/VT1507A for bridge completion, a second SCP is
required to make the measurement connection. You can use
the following SCPs for this type of static strain measurements:
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949 • 955 • 1VXI
64-channel Scanning A/D Converter
• VT1503A 8-channel Programmable Filter/Gain SCP
• VT1506A 8-channel 120 Ω Strain Completion &
Excitation SCP
• VT1507A 8-channel 350 Ω Strain Completion &
Excitation SCP
• VT1508A 8-channel 7 Hz Fixed Filter & x16 Gain SCP
• VT1509A 8-channel 7 Hz Fixed Filter & x64 Gain SCP
standard first calibrates the on-board calibration source. Then
built-in calibration routines use the on-board calibration source
and on-board switching to calibrate the entire signal path from
the scanning A/D’s input, through the signal conditioning plugons (SCPs) and FET MUX, to the A/D itself. Subsequent daily or
short-term calibrations of this same signal path can be quickly
and automatically done using the internal calibration source
to eliminate errors introduced by the signal path through the
SCPs and FET MUX, or by ambient temperature changes. All 64
channels can be quickly and productively calibrated to assure
continued high-accuracy measurements.
By using the latest surface mount technology in circuit
design, it has been possible to combine 48 channels of
strain conditioning into a single 19-inch rackmount enclosure
that is only 1 ¾ inches high. This includes programmability
of individual strain bridge configuration and completion,
and an on-board calibration source.
In addition to the calibration of the signal path within the
scanning A/D, the VT1413C allows you to perform a “Tare Cal”
to reduce the effects of voltage offsets and IR voltage drops in
your signal wiring that is external to the scanning A/D. The Tare
Cal uses an on-board D/A to eliminate these voltage offsets.
By placing a short circuit across the signal or transducer being
measured, the residual offset can be automatically measured
and eliminated by the D/A. Tare Cal should not be used to
eliminate the thermoelectric voltage of thermocouple wire on
thermocouple channels.
Transient Measurements
When making higher speed measurements, a vital issue
often is the time skew between channels. Ideally, in many
applications, the sampled data is needed at essentially the
same instant in time. The intrinsic design of the VT1413C
provides scanning of 64 channels with maximum skew of
640 µs between the first and last channels, far less than
most sampled data systems.
Twelve VT1413C modules may be used in a 13-slot, C-size
mainframe for a total of 768 channels. A C-size configuration
using MXIbus allows you to link together multiple mainframes
on a single backplane for larger scanning A/D systems
Note: For field wiring, the use of shielded twisted pair wiring is
highly recommended.
For applications requiring large channel counts of strain
measurement, the EX1629 provides a more cost effective
approach to static (and dynamic) strain measurements.
Transient Voltage Measurements
The VT1510A provides basic sample-and-hold capabilities
on four channels. Six-pole Bessel filters provide alias and
alias-based noise reduction while giving excellent transient
response without overshoot or ringing. The VT1510A can
be used in strain applications primarily where the bridge is
Timing Signals
Scan-to-scan timing and
sample-to-sample timing can be set
Scan triggers:
Can be derived from a software
command or a TTL level from
other VXI modules, internal timer,
or external hardware. Typical
latency 17.5 µs.
Multiple VT1413C modules can be
synchronized at the same rate
using the TTL trigger output from
one VT1413C to trigger the others.
Multiple VT1413C modules can be
synchronized at different integerrelated rates using the scan
timer/N mode and the TTL trigger
output from one VT1413C module
to trigger the others.
Transient Strain Measurements
The VT1511A and VT1521, double-wide SCPs, have all
the capabilities of the VT1510A but add on-board bridge
excitation and completion functions. The four direct input
channels are used for monitoring the bridge excitation. A
maximum of four SCPs (16 channels) can be installed on a
Automated Calibration for Better Measurements
The VT1413C offers superior calibration capabilities that
provide more accurate measurements. Periodic calibration of
the scanning A/D is accomplished by connecting an external
voltage measurement standard (such as a highly accurate
multimeter) to the inputs of the scanning A/D. This external
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949 • 955 • 1VXI
64-channel Scanning A/D Converter
Scan Triggers
100 µs to 6.5536 s
100 µs
Trigger count:
1 to 65535 or infinite
Sample Timer
10 µs to 32768 ms
0.5 µs
Measurement Specifications
Measurement Accuracy
The following specifications include the SCP and scanning
A/D performance together as a unit. Accuracy is stated for
a single sample. Averaging multiple samples will improve
accuracy by reducing noise of the signal. The basic VT1413C
scanning A/D has a full-scale range of ±16 V and five autoranging gains of x1, x4, x16, x64, and x256. An SCP must be
used with each eight channel input block to provide input
protection and signal conditioning. Refer to the information
on each individual SCP for measurement specifications.
Specifications are 90 days, 23 °C ± 1 °C, with *CAL done after
a 1 hr warm-up and CAL:ZERO done within 5 minutes. Note:
Beyond the 5 min limitation and CAL:ZERO not done, apply
the following drift error: Drift = 10 µV/°C ÷ SCP gain, per °C
change from CAL:ZERO temperature.
Measurement resolution:
16 bits (including sign)
Maximum reading rate:
100 kSa/s divided
by the number of
channels in the scan.
For example:
100k/64 = 1.56 k/Sa/s per channel
100k/16 = 6.25 k/Sa/s per channel
64 kSa
Maximum input voltage:
Normal mode plus
common mode
±16 V peak
±42 V peak
Damage level:
Maximum common mode voltage:
Damage level:
±16 V peak
±42 V peak
SCP input impedance:
100 mΩ differential
Maximum tare cal offset:
Phase jitter scan-to-scan:
Phase jitter card-to-card:
62.5 mV range ±75% of
full-scale other ranges
±25% of full-scale
Accuracy Data
Measurement accuracy is dependent upon the SCP module
used. Refer to the accuracy tables and graphs for the
individual SCP to determine the overall measurement
Many definitions of accuracy are possible. Here we use singleshot with 3 sigma noise. To calculate accuracy assuming
temperature is held constant within ±1°C of the temperature
at calibration, the following formula applies:
Single Shot 3σ = ±(√((GainError)2 + (OffsetError)2+
Correcting for Temperature
To calculate accuracy over temperature range outside the
±1 °C range, results after *CAL are given by replacing each of
the above error terms as follows:
(GainError)2 + (GainTempco)2
(OffsetError)2 + (OffsetTempco)2
Power Available for SCPs
80 ps rms
41 ns peak 12 ns rms
±24 V:
5 V:
3.5 A
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949 • 955 • 1VXI
64-channel Scanning A/D Converter, C-Size
VXI Characteristics
VXI device type:
Register based
Data transfer bus:
Shared memory:
VXI buses:
TTL Trigger bus
VXIplug&play with
Source Code
Instrument Drivers - See the VXI Technology Website
www.vxitech.com for driver availability and downloading.
73-0024-002, Option 011 Screw Terminal Connector Block
73-0024-003, Option 013 Spring Clamp Terminal Connector
73-0024-004, Option A3F Interface to Rackmount Terminal
Ordering Information
Scanning A/D Converter, includes spring clamp terminal block
Scanning A/D Converter, includes screw connector terminal block
Interface to rackmount terminal panel
8-channel Direct Input SCP
8-channel 7 Hz Low-pass Filter SCP
8-channel Programmable Filter/Gain SCP
8-channel Current Source SCP
8-channel 120 Ω Strain Completion & Excitation SCP
8-channel 350 Ω Strain Completion & Excitation SCP
8-channel x16 Gain & 7 Hz Fixed Filter SCP
8-channel x64 Gain & 7 Hz Fixed Filter SCP
4-channel Sample & Hold Input SCP
4-channel Transient Strain SCP
8-channel 25 Hz Fixed Filter SCP
8-channel ÷ 16 Fixed Attenuator & 7 Hz Low-pass Filter SCP
4-wire Resistance Measurement SCP
4-channel High-Speed Bridge SCP
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