Rockwell Automation EK-44750C Enwatch Unit - Manual (Page 5)

Rockwell Automation Publication GMSI10-IN001A-EN-P - May 2013
Enwatch Unit 5
The circuit board is a completely self-contained, 16-channel analog input to
Ethernet interface, including power regulation and local communication
facilities. Each block of the diagram in
Figure 1 on page 4 is described below.
Table 1 - Electrical Block Descriptions
Block Description
ICP interface Each of the 16 channels has its own ICP interface that is capable of powering a typical
two-wire ICP transducer. The nominal voltage is 24 V with a constant current of 3.6
mA. A typical transducer has a bias voltage value of around 11 V, so that the system
can accommodate a full ±10V input range. The ICP interface can be disabled for AC
and DC coupling of voltage signals.
Multiplexer The multiplexer circuit selects one of the 16 input channels under software control.
All inputs are over-voltage and ESD protected.
High-pass filters Four software-programmable high-pass filters (0.36 Hz, 2.67 Hz, 5.3 Hz, and 23.8
Hz) are available to remove unwanted low frequency signals.
Integrator An on-board hardware integrator is available for getting a velocity measurement
from an accelerometer, as well as displacement from a velocity sensor. The host
software can perform a second level of integration if required.
Spike Energy™ function (gSE™) gSE provides a conditioned signal suitable for measurement of bearing condition.
Anti-aliasing filter This filter removes high-frequency components from the incoming analog signal
that can alias back into the sampled signal, resulting in incorrect data in the
spectrum. The filter has a very high roll-off and removes all alias effects in standard
sampling/spectral analysis applications.
Analog-to-digital converter
(ADC) The ADC samples up to 51.2 kHz and has 16-bit resolution, providing a theoretical
dynamic range of 96 dB.
Clock generator The timer varies the sampling rate under microprocessor control. Sampling can be
synchronized to one of 4 external triggers (typically a once-per-rev TTL signal from a
rotating shaft). This system can also take a preprogrammed number of samples per
revolution. The external trigger acts as a tachometer to determine shaft speed. Pre
and post-trigger functions are available.
Gain amplifier The Enwatch unit automatically sets the input gain in auto-range mode as each
channel is selected by the multiplexer.
Microprocessor subsystem This contains the microprocessor, flash memory, and SRAM memory. The
microprocessor controls the Enwatch unit under instructions stored in the flash
memory. The SRAM memory acts as a temporary data storage area if buffering is
required before data is transferred over the network.
Watchdog The microprocessor subsystem incorporates a watchdog that, if a power glitch or
other external effect interrupts the system, automatically resets without the need for
user intervention.
Ethernet controller/buffer
memory/10Base-T These functions control data transfer over the Ethernet network. The system uses the
UDP/IP standard protocol and implements 10 Base-T as the physical network layer.
Power regulation Input DC power is derived from an AC to DC converter and the Power Regulation
function provides the secondary DC voltages as required.