Span Data - Siemens SITRANS F Instruction Manual

Section 2

2.7.1 SPAN DATA

The Span Data menu allows you to set 0% and 100% output limits for energy rate (Ve), volumetric flow
(Vfo), absolute flow (Vfab) and sonic velocity (Vs). Each menu cell shows appropriate rate units and
time base. If you change flow rate units after spanning the system, the computer automatically updates
the output data setup to reflect the change. Span limits apply to both the analog outputs and the on-
screen stripchart. The flow outputs operate as follows:
Ve
Spanned Energy Rate:
Ts, Tr, Td
Spanned Supply,
Return Delta
Temperature:
Vfo
Spanned Volumetric
Flow Rate:
Vfab
Spanned Absolute
Volumetric Flow
Rate:
Vs
Spanned Liquid
Sonic Velocity:
Maximum span values represent:
100% of span
Current output of 20 mA
Voltage output of 10 Vdc
Pulse output of 5000 Hz
These entries establish the Ve span. The [Max Energy Flow] menu cell
sets 100% of span while the [Min Energy Flow] menu cell sets 0% of
span. Use signed numbers for bi-directional spanning. Note that negative
(reverse) energy is always lower than positive energy, whatever its abso-
lute magnitude. For example, for a flow measurement range of -30 KBTU
to +10 KBTU, the 4 mA span will be -30 KBTU, and the 20 mA span will be
+10 KBTU.
Use these cells to span the two temperatures, Ts and Tr, and the com-
puted temperature difference, Td. Use signed numbers for bidirectional
spanning.
The minimum and maximum flow rate entries establish the Vfo span. The
[Max Flow] menu cell sets 100% of span. The [Min Flow] menu cell sets
0% of span. Use signed numbers for bi-directional spanning. Note that
negative (reverse) flow always is lower than positive flow, whatever its
absolute magnitude. For example, for a flow measurement range of -30
GPM to +10 GPM, the 4 mA span will be -30 GPM, and the 20 mA span
will be +10 GPM.
Vfab is the absolute magnitude of the volumetric flow rate (Vfo). There
are no menu cells provided to span this output. Vfab shares the Vfo span
entries. The Vfab minimum span is always zero. The maximum span for
Vfab is the largest absolute value of either the min. or the max. flow rate
(Vfo) entries. For example, a span between +10 GPM and -30 GPM, spans
the Vfab output from 0 GPM to 30 GPM.
Vs is the sonic velocity in meters-per-second (m/s) of the flowing liquid.
The min. and max. Vs entries establish the Vs span. Max Vs (m/s) de-
fines 100% of span. The Min Vs (m/s) defines 0% of span.
2-46
Minimum span values represent:
0% of span
Current output of 4 mA
Voltage output of 0 Vdc
Pulse output of 0 Hz
1010ENFM-3B