VTI Instruments EX1629, Руководство пользователя

Страница: 16 / 346

VTI Instruments Corp.
16 EX1629 Introduction
Excitation Source
The EX1629 features bridge excitation, programmable and regulated on a per channel basis. The
positive and negative excitation voltages are independently programmed from 0 V to +8 V and
0 V to -8 V, respectively, with current capability of 50 mA per channel. This programming
independence provides the flexibility of balanced or imbalanced excitation. Finally, remote sense
lines on each input connector can be employed for improved half-bridge and full-bridge
performance.
Programmable Bridge Configurations
Complete bridge configuration support is selectable under program control on a per channel basis.
Options include full, half, quarter120, quarter350, and quarterUser bridges. Moreover, a high
impedance voltage mode provides direct voltage measurements up to ±15 V.
Self-calibration
In order to deliver high measurement accuracy over a wide ambient operating temperature range,
the EX1629 provides the ability to perform an instrument self-calibration. During self-calibration,
the input signal conditioning paths are disconnected from the input jacks and connected instead to
a calibration bus that is driven by an internal calibration source. Through measurement of the
conditioning paths at multiple calibration source points, software compensation for circuitry drift
since the last full calibration is conducted. This provides a significant accuracy improvement
without the burden of connecting external equipment. Moreover, the self-calibration process
completes quickly and does not require removal of the actual input connections, making it
convenient to run often.
Confidence Measurement System
In addition to the main bridge measurement path, the EX1629 provides a unique, secondary
measurement system that operates in parallel. This “confidence” measurement system provides the
key bridge parameters of excitation voltage, excitation current, and common mode voltage and can
provide verification of the integrity of the bridge and cable connections. Because the confidence
system employs its own ADC, it has no effect on the sampling characteristics of the main bridge
input.
Shunt Calibration
The traditional shunt calibration process is supported to ensure correct bridge performance. Each
input channel provides a unique, precision 55 kΩ resistor that can be programmatically connected
locally for quarter-bridge shunting or remotely for full- or half-bridge shunting. Moreover, an
external resistor may be connected into each of three front panel connectors, one for each group of
16 input channels. Similarly, this front panel resistor may be programmatically connected locally
or remotely.
Wideband Output
Each channel of the EX1629 has a high-performance analog wideband buffered output that can be
connected to a high-speed digitizer for measuring structural vibration levels. The wideband
outputs are accessible on the rear panel of the instrument via three 44-pin D-Sub connectors.
Multiple Gain Ranges
Each channel is independently programmable with a signal conditioning gain of 1, 10, or 100.
This provides application flexibility to make high resolution strain measurements as well as direct
voltage measurements.