Seametrics AO55 Instructions

General Information
The SeaMetrics AO55 is a blind (non-indicating)
4-20 mA transmitter, designed for use with almost all
SeaMetrics flow sensors. It accepts a pulse frequency
input from the flow sensor, and converts this input into a
continuous analog output signal. Power for the transmitter
is taken from the current loop itself, so only two wires
are required. The digital design makes it possible to span
the unit in the field without tools. The frequency at which
20 mA is desired is entered on a set of rotary switches,
and an internal microcontroller automatically scales all
other values accordingly. An additional benefit of the
microcontroller is its ability to average inputs, for
smoothing of the output signal. The degree of averaging
can be selected in the field, from 2 to 16 seconds.
For maximum environmental protection, the electronic
components are encased in a special semi-flexible
urethane potting material. The housing is cast from
aluminum and fuse-coated. The clamshell housing is
connected directly to the flow sensor or, in the wall mount
version, provided with mounting feet.
The AO55 will operate on a relatively wide range of
current loop voltages, 12 to 36 VDC. However, lower
Features
Digital span setting
AO55 Blind Analog
Transmitter Instructions
voltages limit the load that can be applied to the loop
without distortion of the signal. (See chart on page 4 if
there is a question regarding voltage vs. load.) A built-in
power regulator supplies the appropriate power to the
flow sensor.
Typical applications for this transmitter are telemetry (or
SCADA), distributed control systems, programmable
controllers, data logging, and chart recording.
Specifications
Power
Temperature
Input
Minimum Frequency
Maximum Frequency
Output
Frequency Setting
Input Averaging
Response Time
0 0 0 0
Frequency
AO55
Power
12 - 36 VDC
32° - 130°F (0° - 55°C)
open-collector solid-
state
10 Hz (@20 mA)
999.9 Hz
proportional 4-20 mA
4 rotary DIP switches
2 - 16 seconds
(switch selectable)
2-60 seconds
90% of full scale
(dependent on input
averaging)
Potted module for
moisture protection
Loop indicator light
Field-set
averaging time
LT-10604-A
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