The collapse of the I-35 bridge in Minneapolis on August 1 was a catastrophe.
But it should provoke a greater effort to monitor the movement and stresses
of buildings, bridges, and rail tracks using strain gauges, piezo sensors, and
other inputs receiving vibration sensor data. For designers, that means a need
for low-frequency and ultra-low-frequency filters.
The eponymously named AnadigmFilter1 chip set is available as a circuit-board
module as well. It combines Anadigm's dynamically programmable Analog Signal
Processor (dpASP) technology and a state machine to enable designers to quickly
create a dynamically programmable filter for frequencies from dc to 600 kHz.
Filter types comprise sixth-order, low-pass, band-pass, high-pass, or band-stop
circuits with Butterworth, Bessel, Chebyshev, or inverse Chebyshev characteristics.
The band-pass and band-stop filters provide two pass/stop bandwidths and the
ability to configure the circuit to bypass mode.
Designers can choose either of two fixed input stages and set them up for gain
or attenuation, level shifting, single-ended to differential conversion, or
first-order low-pass or high-pass filtering by means of external resistors and
capacitors. Inside the dpASP chip, a sixth-order filter is programmed either
by using the DIP switches, by hardwiring, or, if one wants to sweep the frequency
response, dynamically from a controller.
Adjusting the internal clock dividers or changing the external reference clock
permits larger, discrete changes in filter frequency. The accuracy of filter
gain and corner frequency is typically better than 1%.Typical operating power
is 200 mW, with a low-current standby mode.
Structural monitoring is a hot topic.
But using the AnadigmFilter1 as a board
or in a custom configuration also could
benefit applications with ultrasonic,
acoustic, or other low-frequency signals
that require filtering.
In quantities of 1000 units, the
AN231E04 dpASP and AN236C04 state
machine are priced at $11.28 each. The
AN236K04-EVAL2 evaluation board
costs $199. All three products are available directly from Anadigm or from
NuHorizons.
Anadigm
www.anadigmcom
NuHorizons
www.nuhorizons.com