Calculating The Resistance Value - Beckhoff EL3692 Manual

Commissioning
5.8.4

Calculating the resistance value

The terminal calculates the value of the ADC (filtered, X
(Offset ) and the manufacturer gain Gain (Gain
Vendor
are also taken into account.
The two calculations can be activated or deactivated via CoE object 0x80n0:01 [} 168] and 0x80n0:02
[} 168].
X = (X - Offset
Vendor adc Vendor
X = X (object 0x80n0:01 [} 168] deactivated)
Vendor adc
PDO = (X - Offset
Vendor User
PDO = X (object 0x80n0:02 [} 168] deactivated)
Vendor
This is followed by scaling for the INT value and the REAL value.
Note: the unit of X, Offset, Gain depends on the resolution (see chapter Resolution [} 156]).
Extended measuring range
All measuring ranges have an option to extend the range by 10% beyond the upper limit. This range is used
to allow for the hysteresis of the Autorange function.
If the measured value is within extended measuring range, the Extended Range bit is set to TRUE.
Left-aligned presentation
The extended measuring range cannot be used in left-aligned mode.
In this case the Autorange function operates without the 10% measuring range extension. This
combination is not permitted.
INT value
The measured value is displayed based on the set presentation.
Presentation Meaning
0: left-aligned 31 bit+sign, end value:0x7FFFFF00 (extended
measuring range cannot be used)
1: right aligned 24 bit+sign, end value:0x7FFFFF
2: scaled 1 bit / µΩ Measured value in µΩ (upper limit at 2.147 kΩ)
3: scaled 1 bit / mΩ Measured value in mΩ (upper limit at 2.147 MΩ, not
recommended for measuring ranges below 10 Ω)
4: scaled 1 bit / Ω Measured value in Ω (not recommended for
measuring ranges below 10 kΩ)
5: as REAL value The calculated REAL value is entered instead of the
INT value.
Table 3: Presentation
Only the REAL representation covers the whole measuring range including the measuring range with
uniform accuracy.
REAL value
The following equation is used for calculating the REAL value from the value that has already been offset
against the manufacturer and user values (F
1 kΩ, 10 kΩ, 100 kΩ, 1 MΩ and 10 MΩ):
-23
Y =Y * F * 2
real A scal
154
) * Gain / 0x10000 (object 0x80n0:01 [} 168] activated)
Vendor
) * Gain / 0x10000 (object 0x80n0:02 [} 168] activated)
User
the respective full scale value (100 mΩ, 1 Ω, 10 Ω, 100 Ω,
scal
Version: 3.1
) with the manufacturer calibration offset
adc
). The user offset (Offset
Vendor
) and user gain (Gain
User
Example
1,000,000,000 ~4.7 kΩ (range
dec
4)
5,000,000 ~6 kΩ (range 4)
dec
1,000,000 =1 Ω
dec
1,000,000 =1 kΩ
dec
1,000,000 =1 MΩ
dec
-
)
User
EL3692