Emerson Micro Motion SGM Series Configuration And Use Manual page 42

Purging and calibration
Example: Calculating the control pressure for natural gas
Table 5-2: Control pressure and measurement error calculations for natural gas
Gas
Specific gravity range
DTC (kg/m³/°C)
Control pressure at 20 °C
Density range at 20 °C
Measurement error (% of
full-scale
specific gravity/°C )
Total error (%)
Example: Calculating the control pressure for an N
Table 5-3: Control pressure and measurement error calculations for an N
Gas
Specific gravity range
DTC (kg/m³/°C)
Control pressure at 20 °C
Density range at 20 °C
Measurement error (% of
full-scale
specific gravity/°C )
Total error (%)
34
Natural gas
0.55 to 0.8
−0.0003
lb/in² absolute
Bar absolute
kg/m³
Temperature coefficient
Gas compressibility of sam-
ple gas
Velocity of sound in sample
gas
Reference chamber or relief
valve
N /CO mix
2 2
1.0 to 1.5
−0.0003
lb/in² absolute
Bar absolute
kg/m³
Temperature coefficient
Gas compressibility of sam-
ple gas
Velocity of sound in sample
gas
Reference chamber or relief
valve
18 30
1.2 2
0.79 to 1.15 1.32 to 1.92
−0.026 −0.016
±0.0003 ±0.0003
−0.003 −0.003
0.007 0.007
−0.022 −0.012
/CO mix
2 2
/CO
2
18 30
1.2 2
1.44 to 2.16 2.4 to 3.6
−0.014 −0.008
±0.002 ±0.004
−0.005 −0.005
0.007 0.007
−0.014 −0.006
®
Micro Motion Gas Specific Gravity Meters (SGM)
60 100
4 7
2.64 to 3.84 4.62 to 6.72
−0.008 −0.004
±0.001 ±0.002
−0.003 −0.003
0.007 0.007
−0.005 to −0.002 to
+0.003 0.000
mix
2
60 100
4 7
4.8 to 7.2 8.4 to 12.6
−0.004 −0.002
±0.008 ±0.015
−0.005 −0.005
0.007 0.007
−0.010 to −0.015 to
+0.006 +0.015