Measuring Operation - Ahlborn ALMEMO 2470-1S Operating Instruction

Functions
Limit values and alarm
Per measuring channel two limit values can be set (1 maximum and 1 minim-
um). In the event of one of these limit values being exceeded the beeper
sounds and the display backlighting changes from white to red. This alarm
status can be cancelled at the touch of a button. The type of measured value
error is now shown by its color; red means a limit value overshoot, blue means
a limit value undershoot. Various alarm outputs are supported - even in sleep
mode. Relay output modules provide the associated alarm contacts; these can
be allocated individually to specific limit values. Hysteresis is set by default to
10 digits; however, this can be adjusted to any value between 0 and 99 digits.
The exceeding of a limit value can also be used to automatically start or stop
measured value recording.
Sensor locking
All sensor data stored in the EEPROM in the plug can be protected - by means
of a graduated locking function - against undesired access.

5.1.2 Measuring operation

Up to 4 measuring channels are available per transducer; i.e. it is also possible
to evaluate double sensors, individually scaled sensors, and sensors with func-
tion channels. The user can move forwards or backwards from one measuring
channel to the next using the keypad. The selected measuring point is by de-
fault assigned preferred status and is scanned at half the measuring rate; all
other active channels are also scanned but in the background (semi-continu-
ous mode). Data is output on the display and also, if available, to an analog
output. To shorten the response time when there are several measuring points
the measuring rate can be set to continuous and increased accordingly.
Measured values
The measured value for the selected measuring point is shown continuously
with zero-point correction and, as and when necessary, with measured value
correction.
With most sensors, sensor breakage is detected automatically (except for
plugs with shunt, dividers, or additional electronics).
Analog output and scaling
Each measuring point can be scaled by means of analog start and analog end
in such a way that the measuring range thus defined covers the full range of
the analog output (2 V, 10 V, or 20 mA). At the analog output the device can
output the measured value from any measuring point or a programmed value.
Measuring functions
With some sensors, to achieve optimal measured value acquisition, certain
special measuring functions are required. Cold junction compensation is
provided for thermocouples; temperature compensation is provided for dynam-
ic pressure, pH, and conductivity probes.
Atmospheric pressure compensation is provided for humidity sensors, dynamic
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