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Installation
4.4 Basic Model
The standard model is available for °C or °F. It
provides a 2 pin screw-jumper terminal for
connecting the 4 to 20 mA current loop. The polarity
is indicated on the panel.
Above the screw-jumper terminal there are two
rotary switches for emissivity setting. Emissivity is
preset at the factory at 0.95 (see figure). The appendix
Figure 6: Back panel of basic model
lists typical emissivity values for common materials,
see appendix see section 9.2
Typical Emissivity
Values, page 42.
4.4.1 Installation with a Controller
Basic model
Shield
Controller
Figure 7: Typical installation of basic model
4.5 Smart Model
The Smart model has a 3 pin screw-jumper terminal
for connecting the 4 to 20 mA current loop and the
alarm output. The terminal assignment is marked on
the panel. To allow clip leads from a HART adapter to
attach directly to the sensor for setting sensor
parameters, raise the removable terminal strip about
4 mm (0.2 inches) from the rear panel board and
connect across the exposed (+) and (-) pins. For
Figure 8: Back panel of basic model
example, via line terminals, a lap-top with a HART
adapter can be used for programming the sensor.
4.5.1 HART Protocol
Originally, transmission of information was in one direction only, from sensing head to process control.
The parameters monitored for the production of a product were not changed. In order to use the same
technological equipment to manufacture a multitude of differing products, it must be possible to
quickly alter many process parameters. This has an effect on the sensing head. Measuring range,
accuracy and alarm values must be redefined. It would be extremely inconvenient if it were necessary
to reprogram the sensing head at the unit every time. The HART protocol arose from this requirement.
It allows the application of "intelligent" sensors. The sensing heads can be programmed from the control
room. This means that information is transmitted in two directions. The sensing head provides analog
measured values to the control room via the 4 to 20 mA current loop. The sensing head can be
reprogrammed from the control room by means of bi-directional transmission of digital signals. The
superposition of analog and digital signals is described by the HART protocol. Sensors which are
programmable in this way are called SMART sensors. Apart from the Smart model, a HART/RS232
TX
19
info@Raytek-Direct.com
1.888.610.7664
Rev. O7 07/2017
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