Table of Contents
Advertisement
5.4 "Filter" and "Oversampling"
A first order low-pass filter in the hardware limits the fre-
quency range at the input of the analog digital converter
(ADC). The filtered signal is present at the analog digital con-
verter.
Depending on the setting of the value "Oversampling factor"
in the object "Device settings" (F800:01), the Oversampling
of the ADC can be set. If Oversampling is switched on, the
ADC samples multiple values and transmits the average of
the measured values. A ratio of 0 disables the Oversampling.
2 means for example that two Samples can be read in per
transferred process date. Thus, the effective useful signal fre-
quency can be restricted.
5.5 Limit value check of the upper and lower
range limit
The ADC input data is used to check whether the values are
above or below the valid range. The status bits "Overrange"
and "Underrange" or "Wire break" are set accordingly in the
process data. There are different values at which the diagnos-
tics is set and reset.
For the limits, go to the chapter "Distinctive values and data
formats".
5.6 User Scale: Gains and offset adjustment
The "User Scale" functionality allows an individual correction
of the gain (User Gain) and the offset (User Offset) for each
channel.
User gain
Fig. 4: User Gain and Offset
Enable the functionality "User Scale" to apply the correction.
Therefore, set the parameter "80x0:05 User scale enable" to 1.
Enable the "User Scale" functionality to apply the correction.
You have to set the parameter "80x0:05 User scale enable" to
1.
Output values to calculate the gain and the offset:
Value_Range:
Scaled_Value_Range:
Lower_Range_End_Value:
Scaled_Lower_Range_End_Value: The desired value at the lower end of the
The values for gain and offset are calculated as follows:
= Scaled_Value_Range ÷ Value_Range
Gain_Factor
= (Gain_Factor × 10000) − 10000
User_gain
Enter the value "User_gain" into the parameter "80x0:01 User
gain".
= (Scaled_Lower_Range_End_Value) −
Offset
(Lower_Range_End_Value × Gain_Factor)
= Offset × 1000
User_offset
Enter the value "User_offset" into the parameter "80x0:02 User
offset".
Note that possible limitations of the value range also remain
after the "User scale" limitation. For more detailed informa-
tion, refer to .
The settings can only be made in the "Pre-Op" state and
should be written upon each start of the EtherCAT bus via the
start parameter.
User offset
User scale
enable
The value range at the input of the "User
Scale" calculation
The desired value range at the output of
the User Scale calculation
The value at the lower end of the input
value range
output value range
Example 1:
Module is XI422204, analog output with ±10 V.
The target is to reduce the value range to values between
-3V and +8V. The values of the application still uses the
value range from −10 V to +10 V.
Input signal to User Scale calculation
Signal after Gain calculation
Output signal after offset calulation
-10
-8
Fig. 5: Value range offset from -10 V...+10 V to -3 V...+8V
Value_Range
Scaled_Value_Range
Lower_Range_End_Value
Scaled_Lower_Range_End_Value
Gain_Factor
User_gain
Offset
User_offset
Example 2
Module is XI342204, analog input from 4 to 20 mA.
The connected system specified 4.5 mA as minimum value
and 18.5 mA as maximum value. The values should be
mapped to a value range from 4 to 20 mA.
Input signal to User Scale calculation
Signal after Gain calculation
-1,143 mA
Output signal after offset calulation
0
2
Fig. 6: Value range offset from 4.5 mA to 18.5 mA to from 4
mA to 20 mA
Value_Range
Scaled_Value_Range
Lower_Range_End_Value
Scaled_Lower_Range_End_Value
Gain_Factor
User_gain
Offset
User_offset
5.7 Limit 1/2 Threshold Check
There are two individual and independent limit value checks
per channel specifying whether the process data value is
lower, equal to or higher than the limit value set.
The limit value to be checked in set in the parameter "Limit
1" or in the parameter "Limit 2" of the object "Channel x set-
tings". The format is identical to the value in the process data,
a standardized value.
Each individual limit check is enabled using the parameter
"Limit y enable" in the object "Channel x settings".
The result of the check is output in the process data "Ch.
x Limit y". Alternatively, it can be retrieved either via the
CoE object 60x0:04 ("Channel x Limit 1") or the CoE object
60x0:06 ("Channel x Limit 2"). Meaning of the bits:
Bit
Meaning
0
1 if the value is lower than or equal to the set date.
1
1 if the value is higher than or equal to the set date.
x 0,55
+2,5 V
-6
-4
-2
0
2
4
6
= 10 V − (−10 V) = 20 V
= 8 V − (−3 V) = 11 V
= −10 V
= −3 V
= 11 V ÷ 20 V = 0.55
= (0.55 × 10000) − 10000 = −4500
= (−3 V) − (−10 V × 0.55) = 2.5 V
= 2.5 × 1000 = 2500
x 1,1429
4
6
8
10
12
14
16
18
= 18.5 mA − (−4.5 mA) = 14 mA
= 20 mA − (−4 mA) = 16 mA
= 4.5 mA
= 4 mA
= 16 mA ÷ 14 mA = 1.1429
= (1.1429 × 10000) − 10000 = 1429
= 4 mA − (4 mA × 1.1429) = −1.143
= −1.143 × 1000 = −1143
R911418827, Edition 01, 3 / 8
8
10
U/V
I/mA
20
Advertisement
Table of Contents
