Power Supply; Main Power Supply; Back-Up Batteries - SARAD Smart Radon Sensor Manual

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Power supply

Main power supply

The smart Radon Sensor requires an external power supply in range from 12V up to 24V. The
maximal current consumption does not exceed 50mA (including 20mA of current loop's maximal
signal and active LEDs, but without usage of the CO2 sensor).
The connection ports for a power supply are shown in figure 1 and defined in table 2. Two ports of
the terminal block with the description „DC-„ and „DC+", at the device`s front panel, are ground and
positive potential respectively. It is recommended to use the power supply unit with a galvanic
isolation for supplying the Smart Radon Sensor. The galvanic isolation is of importance in case the
analogue output is utilized AND the 0..20mA inputs of the data log system are referenced to the
ground potential (e.g.: the current signal is transformed into the voltage value through a defined
resist).

Back-up batteries

The device is equipped with an internal backup power supply (UPS) consisting of two LR3 (AAA)
batteries. This feature allows one to continue the measurement seamlessly if main power supply
failure occurs.
Without DC connection the backup will supply the device for approximately two weeks. In such
circumstances the current loop as well as (if present) CO2 sensor will be deactivated, and the LEDs
functionality will be reduced. If the cell voltage drops below 1,0V, then the current measurement will
be interrupted and the instrument enters the standby mode. Once the main powers supply recovers
or new batteries are placed, the stored measurement data will be accessible immediately.
The instrument accepts alkaline as well as NiCd or NiMH batteries. Attention! Do not use lithium-ion
batteries because their cell voltage is 3V or 3,6V. For maximum operational period we recommend
the usage of alkaline batteries which are optimized for low loads.
It is also recommended to insert the batteries prior to mounting the device and connecting the
terminal block. The placement of the batteries is described more in detail in the next chapter.
Important: The real time clock of the instrument must be set by software after inserting the
batteries. The rechargeable batteries cannot be charged once placed in the instrument. For
stationary operation alkaline batteries are recommended. In contrary to rechargeable batteries, the
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