Beckhoff KS31 2 Series Manual page 16

Product overview
Fluctuating measuring signals interfere with self-calibration
In the calibration phase, the terminal uses a stabilization check to verify that the input signal is sta-
ble. Strongly fluctuating measuring signals prevent a termination of the self-calibration, it stops with
Error=1 and Overload/Underload=1, see chapter
Basics of the function/ Calibration [} 15] and
Access from the user program/ Status byte 1 (for process data mode) [} 44].
If such a signal is expected at the system, the following can be selected
• the self-calibration via control bit CB1.1 [} 44] can be blocked in the process until a steady signal
is applied and the self-calibration runs through.
• the stabilization check can be switched off with bit R32.7 [} 50].
• the stabilization error display can be switched off with bit R32.14 [} 50].
• the tolerance window R48 [} 53] of the stabilization control can be increased.
The functionality of the calibration including all features invariably refers to both channels simultaneously!
The channels cannot be calibrated individually. For this reason, the registers R40 [} 53], R44 [} 53], R47
[} 53] and R48 [} 53] are only implemented once for both channels.
• In the first phase of the calibration, an input voltage of 0 V is applied to both analog inputs (zero
calibration). The zero points of both analog input stages can be determined in this way. For this
measurement, the respective absolute value of the channels is of interest. The value is subsequently
stored in the RAM (register R1 [} 48]).
• During the second calibration phase, an internal reference voltage of approx. 1.8 V (final calibration) is
applied to both analog inputs. In this case, it is no longer the absolute value of the measurement result
that is of interest, but only any deviation from the basic calibration value determined during production
(register R23 [} 50]). The ratio between the two values is calculated and used in the next correction
calculation [} 14]. The value is subsequently stored in the RAM (register R2 [} 48]).
Stabilization of the calibration
During the calibration, a stabilization of the offset and gain values is carried out. The calibration values are
only accepted once a certain number (specified via register R47 [} 53]) of measured values is inside a
certain tolerance range (specified via register R48 [} 53]). This further increases the precision. This function
can be deactivated via bit R32.7 [} 50] .
Limit values
The terminal offers the option of monitoring two limit values per channel. Limit value 1 can be specified via
register R35 [} 52], and limit value 2 via register R36 [} 52]. They are activated via bits in the feature
registers R32.9 [} 50]and R32.10 [} 50]. The status of the current process data value is indicated to the
controller via the status byte SB1 [} 44]. Possible states are: Process data equal limit value (3), process
data less than limit value (2), process data greater than limit value (1).
Limiting the measuring range
The terminal indicates any violation of the measuring range to the higher-level controller via the status byte.
• If the current measured value is larger than 0xFFFF or 0x7FFF, bit SB1.1 [} 44] is set.
• Is the current measured value is less than 0 or 0x8000, bit SB1.0 [} 44] is set.
In both cases, the ERROR LED of the respective channel will be on. This function can be deactivated via bit
R32.8 [} 50].
Differential measurement
With the KL3132, KL3162, KL3172, KL3182, the differential measurement can be deactivated with bit R32.6
[} 50]. Then, for channels 1 and 2, the input is internally switched to GND at terminal point 3/7, which must
then be wired externally accordingly.
16 Version: 2.6.0 KL31x2/KS31x2