ATI Technologies UniSens A12 Series, Руководство пользователя

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Series A12 Unisens 2-Wire Transmitter
O & M Manual - 4 -
Rev-L, 7/15
UniSens transmitters, also designated Series A12, are loop-powered devices capable of
operating from DC power supplies between 12 and 30 VDC. Normally, this transmitter will be powered
from the 24 VDC supply from a plant wide monitoring computer, a data logger, or an alarm systems that
supplies the DC voltage. The output of the transmitter is a 4-20 mA signal which is linear with respect to
concentration over the range of the sensing module.
Construction of the UniSens transmitter is modular to allow simple installation and maintenance
as shown in Figure 1 on the next page. The transmitter electronics is housed in an aluminum shell with
an 11 pin relay plug on the bottom. The outer housing is an explosion-proof and weatherproof enclosure
with a relay base mounted inside. The transmitter electronics module simply plugs into the relay base,
and all wiring connections are made to that base. Figure 1 shows an exploded view of a complete
UniSens transmitter with sensing module.
The sensing elements used in the UniSens are electrochemical sensors manufactured by ATI.
These sensors are designed for use in ambient air or in ventilation ducts at temperatures of -30° to +50°
C (some sensors rated to -40° C, oxygen sensors rated to -10° C) and at relative humidities between 20
and 98% RH. Use of these sensors in extremely dry air or in condensing gas streams is not
recommended.
Each sensing element is incorporated into a snap-in sensing module, which also contains
electronic memory that is read by the transmitter. This memory contains information on what type of gas
sensor is contained in the module, the range of that particular module, and the calibration constants for
the sensor. When the module is snapped into a transmitter, this data is read into the transmitter
electronics and information related to the module is displayed on the LCD display on the transmitter.
Because all calibration data is stored in the sensing module, these modules can be calibrated using any
spare transmitter and simply snapped into any other transmitter for operation. This unique feature
eliminates the need for field calibration.
AUTO-TEST OPTION
UniSens transmitters are available with an optional feature that eliminates much of the manual
response testing required for toxic gas detection systems. This feature is referred to as Auto-Test, and
consists of a miniature electrochemical gas generator close coupled to the sensor. The generator
produces a "puff" of gas when activated by the transmitter. The response of the sensor is monitored
during this test to be sure that it is still responding to the particular gas, and the output of the transmitter is
driven below 3.7 mA if the sensor does not respond. At the same time, the LCD display indicates that
there was an Auto-Test failure.
The Auto-Test sensor check occurs automatically every 24 hours so that the sensor response is
verified daily. In addition, the Auto-Test can be activated manually at any time using the controls on the
front of the transmitter. During the Auto-Test cycle, the 4-20 mA output is held at 4 mA so that receiving
devices do not alarm during the test. Because most users manually test toxic gas sensor response once
a week, the Auto-Test feature can pay for itself very quickly in reduced labor cost.