58
Reference Manual
00809-0100-4772, Rev FA
Transducer Block
March 2016
Transducer Block
Process temperature
Process Temperature and Temperature Units are needed for the electronics to compensate
for thermal expansion of the flowmeter as the process temperature differs from the
reference temperature. Process temperature is the temperature of the liquid or gas/steam
in the line during flowmeter operation.
Process density
Process Density and Density Units are required if you have designated mass units for your
flow rate units. For liquid and gas/steam process fluids, the process density is used for the
conversion from volumetric units to mass units. For example, if you have set flow units to
kg/sec rather than gal/sec, a density is required to convert the measured volumetric flow
into the desired mass flow.
For MTA models, Process Density and Density Units are important when measuring
temperature compensated saturated steam. The Process Density must be set to a nominal
process fluid density so that other parameters such as PV range, Sensor Limits and
Recommended Minimum Low Flow Cutoff can be accurately calculated in flow units. If the
actual process density changes frequently, it may be necessary to set the process density to
the highest expected value. This will allow for the required Sensor Limits of the meter.
Note
The user-entered process density value can also be used as a reference value for optimizing
the digital “signal processing” filters. When optimizing the filters, always select a density
value from the list of choices nearest and below the actual process density.
Damping
Damping changes the response time of the flowmeter to smooth variations in output
readings caused by rapid changes in input. The default damping is 2.0 seconds. This can be
reset to any value between 0.2 and 255 seconds.
The MTA model flowmeter has the additional capability of providing the measured process
temperature. A separate damping for this measurement is provided and can be configured
from 0.4 to 32.0 seconds.
4.4.3 Flow units
Density ratio
Density Ratio is used to convert the actual volumetric flow to standard/normal volumetric
flow rates based on the following equations:
This value must be entered if using Standard or Normal units (SCFM, SCFH, NCMM, NCMH,
NCMD). These units are configured in the AI block. The density ratio can also be calculated
by entering the process and base conditions as described below (The flowmeter electronics
will then calculate the density ratio for you.)
Conversion factor
density at actual (flowing) conditions
density at s dard (base)tan conditions
--------------------------------------------------------------------------------------------------------=
Conversion factor
T
b
P
f
× Z
b
×
T
f
P
b
× Z
f
×
-------------------------------=
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