Omega CT485B-110V-G-AL, Руководство пользователя

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Technical Details
10-1
10
10.1 Sensors and Measurement
The recorder has an external plug-in temperature/humidity sensor. A six-foot
remote sensor cable is provided to allow remote sensing of both temperature and
humidity.
Unlike many circular hygrothermographs, this recorder utilizes electronic
sensors to measure both ambient temperature and relative humidity. The
temperature sensor is a low-power, semiconductor type, with a linear voltage
output proportional to temperature. The humidity sensor consists of a bulk
polymer material deposited on a ceramic substrate. The mobility of the ions in
the polymer changes with moisture content of the surrounding atmosphere. As
a result, the sensor presents an impedance which is a highly non-linear function
of the relative humidity. The sensor is driven by ac excitation and the wide
dynamic range of its output is compressed with a logarithmic amplifier.
All humidity sensors are susceptible to contamination from
outside sources that can affect accuracy and response time.
Take care to prevent excessive contamination by dirt, oil,
grease, solvents, or a corrosive air environment.
The electronically conditioned output of both sensors is fed to a microprocessor
via an analog to digital converter. The processor linearizes and temperature
compensates the output of the humidity circuit employing a “look-up table
approach”. The results of the processor calculations are then used to update the
front panel display and to position the pen arms on the chart paper.
10.2 Pen Arm Drive
This recorder utilizes a motor-driven lead screw pen arm drive located in the
door of the unit. This provides several advantages over conventional pivot arm
mechanisms. First, the recorder pens move along straight, radial lines as the
temperature and humidity change. Thus, the time scales on the chart paper are
straight lines and are much easier for the user to interpret than the swooping
arcs produced by a conventional recorder. Second, the placement of the recorder
pen arms directly opposite one another allows the pen tips to be placed very
close together. This minimizes time offset between information recorded by the
temperature and humidity pens, making the charts easier to interpret. Finally,
the location of the drive mechanism in the door provides an automatic pen lift
when changing the chart paper.
The position of the pen arms on the lead screw mechanism is controlled by
optical encoders. On power up or system reset, the pen arms move to the zero
position. This is detected by a photo interrupter, to provide absolute positional
information to the microprocessor.
NOTE