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LAMBRECHT meteo
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AEM
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8121
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Description
The barometric pressure sensor type (8121) is equipped with a piezoelectric pressure gauge whose characteristics
are linearized by means of a low power microcontroller. In operational mode 0...20 mA or 4...20 mA, output signals
are buffered by a precision operational amplifier with a resolution of 12 bit.
To reduce power consumption in mode 0...2 V the signal is buffered by a separate operational amplifier with very low
quiescent current and the circuitry for current output is completely switched off, thus reducing the quiescent current
of the whole pressure sensor to less than 4 mA (at 1 k
Ω
load). Resolution is 12 bit too. This feature makes the sensor
(8121) particularly suitable for solar powered applications.
The pressure range can easily be set by jumpers to 600...1100 hPa or 800...1100 hPa. For each range the output signal can be
chosen to 0...20 mA, 4...20 mA or 0...2 V.
These settings take place after the next power up of the sensor, that is, after the power supply was switched off for
several seconds. Only at power up new settings are accepted. The sensors power supply lines are protected against
reversed polarity and overvoltage up to 50 V.
The voltage output must not be connected to an external power source. There is always a voltage present at
the voltage output. This voltage is valid only if the appropriate mode (0...2 V output, voltage output mode) is
set.
Settings for mode of operation are done by plug-in jumpers according to the following table.
In case of an error, the sensor switches to low power mode and switches the output to 0 mA and 0 V respectively. The
sensor stays in this mode until the power supply is cycled one time. If the error is fixed, the sensor will proceed with
normal operation after power on.
BLOCK DIAGRAM