Process Control - Ahlborn ALMEMO 710 Operating Instructions Manual

Functions of the ALMEMO 710
menus as measured value list, single display, bar chart, or line graph. Mea-
sured values are acquired automatically with auto-zero and self-calibration;
however, they can also be corrected and scaled as and whenever required.
With most sensors a sensor breakage is detected automatically.
Analog output and scaling
Each measuring channel 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 channel or a programmed
value.
Measuring functions
To achieve optimal measured value acquisition some sensors require certain
special measuring functions. 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 humidity, dynamic pressure, and O2 sensors. With digital D6 and D7 sen-
sors these various compensation measures are performed in the sensors
themselves.
Measured value smoothing
With standard sensors measured values of an unstable, fluctuating nature can
be smoothed by taking a sliding average over a number of values program -
mable from 2 to 99. The averaging period will depend on the conversion rate
and the number of active channels. However, D7 sensors are assigned their
own averaging period for all primary channels; this can be set via the sensor
menu.
Maximum and minimum values
Each measuring operation acquires and stores the maximum and minimum
values with date and time-of-day. These values can then be displayed, printed
out, or deleted from memory.
Average value
Measured values can be expressed as a continuously smoothed sliding aver-
age or as the average obtained over a particular period or cycle or over a se-
ries of specified measuring operations.

5.1.3 Process control

In order to record the measured values from all connected sensors in digital
form measuring channel scanning must be performed continuously with mea-
sured value output according to a time-based process control. The measuring
operation can be started and stopped by means of the keypad, the interface,
an external trigger signal, the real-time clock, or by a specified limit value in-
fringement. The standard cycle, settable from 1 second up, ensures even,
cyclic output. If a higher speed is required, standard sensor values can be out-
put at the conversion rate; however, all sensors can now use the new scan cy-
cle, which obtains measured values from each channel individually according
to its own actual measuring duration.
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