87
12 Supplement
VEGADIF 85 • Profibus PA
53569-EN-230814
F
T
= 0.25 %
3. Determination of deviation and long-term stability
Deviation
Measuring range
TD 1 : 1 up to 5 : 1 TD > 5 : 1
TD > 10 : 1
10 mbar (1 kPa)/0.145 psi
< ±0.1 %
< ±0.02 % x TD
30 mbar (3 kPa)/0.44 psi
100 mbar (10 kPa)/1.5 psi
< ±0.065 %
< ±(0.035 % + 0.01 %) x TD
500 mbar (50 kPa)/7.3 psi
3 bar (300 kPa)/43.51 psi
< ±(0.015 % + 0.005 %) x TD
16 bar (1600 kPa)/232.1 psi
< ±(0.035 % + 0.01 %) x TD
Long-term stability
Measured variable
Time range
1 year
5 years
10 years
Differential pressure
21)
< 0.065 % x TD
< 0.1 % x TD
< 0.15 % x TD
Static pressure
22)
< ±0.065 %
< ±0.1 %
< ±0.15 %
4. Calculation of the total deviation - digital output signal
- 1. step: Basic accuracy F
perf
F
perf
= √((F
T
)
2
+ (F
Kl
)
2
)
F
T
= 0.25 %
F
Kl
= 0.065 %
F
perf
= √(0.25 %)
2
+ (0.065 %)
2
)
F
perf
= 0.26 %
- 2. step: Total deviation F
total
F
total
= F
perf
+ F
stab
F
perf
= 0.26 % (result of step 1)
F
stab
= 0.065 % x TD
F
stab
= 0.065 % x 2
F
stab
= 0.13 %
F
total
= 0.26 % + 0.13 % = 0.39 %
The total percentage deviation of the measurement is thus 0. 39%. The absolute total deviation is
0. 39% of 250 mbar = 1 mbar
The example shows that in practice the error of use can be significantly higher than the actual
measurement error. The causes are temperature influence and turn down.
12.5 Dimensions, versions process component
The following dimensional drawings represent only an extract of the possible versions. Detailed
21)
Relating to the adjusted span.
22)
Relating to the measuring range end value.