VEGA VEGABAR 82 4 … 20 mA_HART - Operating Instructions - Manual (Page 61)

61
9 Diagnosis, asset management and service
VEGABAR 82 • 4 … 20 mA/HART
45028-EN-131010
•
F
T
: Thermal change of zero signal and output span
•
F
Kl
: Deviation
•
F
a
: Thermal change of the current output
You can find the specifications in chapter "Technical data".
Pressure measurement in the pipeline 8 bar (800 KPa)
Product temperature up to 50 °C
VEGABAR 82 with measuring range 10 bar, deviation < 0.075 %
Calculation of the turn down: TD = 10 bar/8 bar, TD = 1.25
1. step: Calculation of the basic accuracy
F
perf
= √((F
T
) 2 + (F
Kl
) 2 )
F
T
= (0.15 %) x (0.5 + 0.5 x TD)
F
Kl
= 0.075 %
F
perf
= √((0.15 %) x (0.5 + 0.5 x TD) 2 + (0.075 %) 2 )
F
perf
= 0.19 %
Step 2: Calculation of the total deviation
F
total
= F
perf
+ F
stab
F
stab
= (0.05 % x TD)
F
stab
= (0.05 % x 1.25)
F
stab
= 0.06 %
F
total
= 0.19 % + 0.063 % = 0.25 %
1. step: Calculation of the basic accuracy
F
perf
= √((F
T
) 2 + (F
Kl
) 2 + (F
a
) 2 )
F
T
= (0.15 %) x (0.5 + 0.5 x TD)
F
Kl
= 0.075 %
F
a
= 0.15 %
F
perf
= √((0.15 %) x (0.5 + 0.5 x TD) 2 + (0.075 %) 2 ) + (0.15 %) 2 )
F
perf
= 0.24 %
Step 2: Calculation of the total deviation
F
total
= F
perf
+ F
stab
F
stab
= (0.05 % x TD)
F
stab
= (0.05 % x 1.25)
F
stab
= 0.06 %
F
total
= 0.24 % + 0.06 % = 0.30 %
9.6 Exchange process assembly with version
IP 68 (25 bar)
With version IP 68 (25 bar), the user can exchange the process as-
sembly on site. Connection cable and external housing can be kept.
Required tools:
•
Hexagon socket wrench, size 2
Practical example
Calculation - Digital out-
put signal
Calculation - Analogue
output signal