3-2 Connectors, Indicators, and Cables
989490
652u & 655u Users Manual
Current Source (IEPE) with Transducer Fault Detection
Note
: IEPE current source can only be enabled when AC Coupling is selected.
If IEPE is selected in software, a constant current is supplied to bias IEPE transducers. The bias current is sourced
through the center conductor of the input channel BNC connector and returns to the conditioning circuit by the outer
conductor. The current source features a voltage operating compliance and is short-circuit and over-voltage
protected as stated in the specifications. Operating compliance refers to the highest voltage that can be sourced
without change of the current source value. In the absence of a transducer, the current source will output a higher
open circuit voltage.
For unused channels and for other applications that do not require bias, the current
source should be disabled from the input via software control, on a per channel basis
.
When the current source is enabled, the input voltage is continuously monitored with level detection circuitry for
indicating an open transducer (high voltage) or a transducer short (low voltage). Existence of either condition
triggers a transducer fault for the associated channel. This error is communicated to the user on the monitor via
software and is also available through a software status request at the end of an acquisition. Faults are detected and
communicated when present. Detection of a fault does not alter the acquisition process or its data.
Input Coupling
The analog input channels can be independently set in software to AC Coupling or to DC Coupling. When AC
Coupling is selected, the input signal passes through a high pass filter. When DC Coupling is selected the high-pass
filter is bypassed.
Anti-Aliasing
The 652u and 655u analyzers each include three-pole anti-aliasing filters and 24-bit sigma/delta analog-to-digital
converters (ADC). The converters exhibit an alias frequency band between 1.69MHz and 6.75MHz, which eases
the requirements of the anti-aliasing filters. Transducers seldom have significant energy at these high frequencies.
However, should there happen to be such energy, the filters will attenuate it. Refer to the specifications chapter for
details, including a response chart.
Analog Triggers
The IOtech 652u and 655u signal analyzers can be triggered per software configuration relevant to the 10 analog
input channels. Refer to the associated software documentation regarding the various types of triggers and how to
set them.
Reference Notes:
For detailed information, refer to the applicable software document, i.e., eZ-TOMAS or eZ-Analyst.
PDF versions of the documents can be accessed via the <View PDFs> button on the Dynamic Signal
Analysis (DSA) CD’s opening screen.
In addition to software documentation, information regarding aliasing, anti-aliasing, sensors,
accelerometers, sound and vibration, and transducers may prove useful to your application. The
internet is a great source for this material.
In regard to TEDS (Transducer Electronic Data Sheet), you may find the IEEE 1451 standard to be of
interest.
