Basler BE1-49, Инструкция по эксплуатации

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3-2 BE1-49 Functional Description
Relay operating power is developed by the wide-range, isolated, low burden, fly-back switching power supply.
Nominal ±12 Vdc is delivered to the relay internal circuitry. Input (source voltage) for the power supply is not
polarity sensitive. A red LED lights to indicate that the power supply is functioning properly.
Power Supply Status Output (Option 2-S)
The power supply status output relay is energized and its NC output contact is opened when power is applied to
the relay. Normal internal relay operating voltage maintains the power supply status output relay continuously
energized with its output contact open. If the power supply output voltage falls below the requirements of proper
operation, the power supply output relay is de-energized, closing the NC output contact.
Constant Current Source
The constant current source provides a regulated 40 mA to the external RTD. This circuit is relatively unaffected
by changes in the ambient temperature. Since resistance of the RTD varies directly with temperature, 40 mA
through the RTD develops a voltage which is proportional to RTD temperature. See Section 5 for a graphical
representation.
Amplifier
The amplifier monitors the voltage across the RTD and provides a voltage level signal to both the upper and lower
temperature limit comparator stages.
Reference Voltage Supply
The reference voltage supply provides a regulated voltage to the UPPER TEMPERATURE LIMIT and LOWER
TEMPERATURE LIMIT front panel controls. Each of these controls is a potentiometer and functions as a variable
voltage divider. The position of the potentiometer wiper determines a reference voltage for one input of the
corresponding comparator circuit.
Upper And Lower Temperature Comparators
Two similar comparators in the relay each compare the amplified voltage across the RTD with a dedicated
reference voltage established by the setting of a front panel control. The upper temperature comparator provides
an output current to its associated driver circuit when the RTD voltage exceeds the reference voltage from the
UPPER TEMPERATURE LIMIT potentiometer. The lower temperature comparator provides an output current to
its associated driver circuit when the RTD voltage is less than the reference voltage from the LOWER
TEMPERATURE LIMIT potentiometer.
Latch (Optional)
A latching function is optionally available for the upper temperature output. When this latch is selected, the upper
temperature output will latch in its energized condition when the upper temperature limit is exceeded. The output
will then remain latched until the RTD temperature falls below its lower limit (as determined by the lower
temperature comparator).
NOTE
If a relay has an older power supply (as indicated above), the RTD measuring
circuit is not isolated from relay input power terminals 3 and 4. If the RTDs are
grounded and the relay power supply is the old style, only a Type E power supply
may be used. Old style Type E power supplies included an isolation transformer
that permitted the RTDs to be grounded. Old style power supplies accepted only
ac input power; new style power supplies accept both ac and dc input power.