Measuring Operations - Ahlborn ALMEMO 5690-2M Operating Instructions Manual

5. Introduction
nominal setpoint or via the scaling menu.
Limit values and alarm
Per measuring channel two limit values can be set (1 maximum and 1 mini-
mum). In the event of one of these limit values being exceeded an alarm sig-
nal is output and relay output modules actuate the associated alarm contacts;
these can be allocated individually to specific limit values. Hysteresis is set by
default to 10 digits but this can be adjusted to any number between 0 and 99.
The exceeding of a limit value can also be used to start or stop measured
value recording automatically or via macros to initiate other specified actions.
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 four 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 mea-
suring channel to the next using the keypad. By default all measuring points
are scanned continuously at a measuring rate of 10 mops and the data thus
obtained is listed on the display. However, if you want to have the measured
values for the selected channel sent to an analog output, it may be an advan-
tage to use semi-continuous mode instead; the output value will then always
be refreshed at half the measuring rate set - irrespective of the number of
measuring points involved.
Measured values
The measured values of 1 to 20 measuring points can be indicated on the dis-
play using a variety of menus, some user-configurable, in three font sizes, and
in the form of a bar chart or line graph. Measured values are acquired auto-
matically with auto-zero and self-calibration; however, they can also be cor-
rected and scaled arbitrarily as required. With most sensors a sensor break-
age is detected automatically.
Analog output and scaling
By means of analog start and analog end any measuring point can be scaled
in such a way that the resulting measuring range covers the full range of the
bar chart or line graph or of an 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 pro-
vided for thermocouples; temperature compensation is provided for dynamic
pressure, pH, and conductivity probes; and atmospheric pressure compensa-
tion is provided for humidity sensors, dynamic pressure sensors, and O sen-
2
sors. On infrared sensors the parameters for zero-point correction and gain
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