Measuring Operations - Ahlborn ALMEMO 2490-1A Operating Instructions Manual

5. Introduction
Sensor locking
All sensor data stored in the connector EEPROM can be protected by means of
a graduated locking function against undesired access.

5.1.2 Measuring operations

For each transducer up to 4 measuring channels are available; i.e. it is also
possible to evaluate double sensors, individually scaled sensors, and sensors
with function channels. You can move forwards or backwards from one meas-
uring channel to the next using the keypad. The selected measuring point is by
default assigned preferred status and is scanned at half the measuring rate; all
other active channels are also scanned but in the background (semi-continuous
mode). The data is output on the display and, 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 autozero and, as and when necessary, with measured value correction.
With most sensors, sensor breakage is detected automatically (except for con-
nectors 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 ther-
mocouples; temperature compensation is provided for dynamic pressure, pH, and
conductivity probes; and atmospheric pressure compensation is provided for humid-
ity sensors, dynamic pressure sensors, and O sensors.
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Measured value smoothing
Measured values of an unstable or strongly fluctuating nature can be smoothed
by means of a sliding average over a number of values programmable from 2 to
99.
Maximum and minimum values
For each measuring operation the maximum value and minimum value are ac-
quired and saved to memory. These values can then be displayed, output, or
deleted from memory.
Measured value memory
Up to 100 measured values can be saved manually. This data can then be
shown on the display or output via the interface.
Differential measurement
It is possible, by setting the measured value to zero, to perform relative meas-
uring operations with respect to a reference value; with 2 sensors and the same
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