E126-P-EL
User Manual
FW_E126-P-EL_M_v0301-01_EN
Page 29
6
FORMULA
6.2 THERMAL EXP.
COEFFICIENT
Enter the thermal expansion coefficient
α
(in 10
-6
/ K) for the liquid used.
The decimal position is fixed.
The default value of 0000.000 disables the volume correction.
Examples: Calculation of the thermal expansion coefficient
:
●
α
for water is 0.00031 per K. Enter: 0310.000
●
α
for petrol is 0.00110 per K. Enter: 1100.000
6.3 T-NORMAL
(TEMPERATURE)
Enter the reference temperature T
normal
with two decimals in Kelvin (K).
In most applications, the volume is calculated at 0°C, which is 273.15 K.
The temperature compensation is disabled with value zero (0).
5.5.8
MENU 7: ANALOG OUTPUT
An analog 4-20 mA signal is generated according to the flowrate with a 12 bits resolution. The
settings for Flowrate influence the analog output directly and should be configured first. The
relationship between rate and analog output is set with the following functions.
7
ANALOG OUTPUT
7.1 OUTPUT
If the analog output is not used, it can be disabled to minimize power
consumption and save battery life. When the output is disabled, a current of
about 2 mA is generated and the unit can still be supplied from this signal
(provided a power supply is connected).
While powering-up the loop, the initial current is approximately 2 mA.
When the output is enabled, it can take a few seconds before the correct
current is generated.
7.2 RATE MIN (4MA)
Enter the flowrate at which the output should generate the minimum signal
(4 mA) – in most applications at flowrate “0”.
The number of decimals displayed depends on the settings in
2.3: FLOWRATE > DECIMALS
.
The measuring units and the time (L/min for example) depend on the
settings in
2.1: FLOWRATE > UNIT
and
2.2: FLOWRATE > TIME
and are displayed
during editing.
If required, you can program the analog output 'up-side-down'. The 4 mA
then represents the maximum flowrate.
For example, enter 800 L/min.
7.3 RATE MAX (20MA)
Enter the flowrate at which the output should generate the maximum signal
(20 mA) – in most applications at maximum flow.
The number of decimals displayed depends on the settings in
2.3: FLOWRATE > DECIMALS
.
The measuring units and the time (L/min for example) depend on the
settings in
2.1: FLOWRATE > UNIT
and
2.2: FLOWRATE > TIME
and are displayed
during editing.
If required, you can program the analog output 'up-side-down'. The 20 mA
then represents the minimum flowrate.
For example, enter 0 L/min.
7.4 CUT-OFF
A low flow cut-off can be set as a percentage of the full range of 16 mA, for
example, to ignore leakage.
When the flow is less than the required rate, the current will be the
minimum signal (4 mA, or 20mA when the analog output is programmed
‘up-side-down’).
CUT-OFF CALCULATION EXAMPLES
Cut-off
Rate-min
4 mA
Rate-max
20 mA
Required rate
before reading
Output
at required rate
2.0%
0 L/min
100 L/min (100-0)*2.0% + 0 = 2.0 L/min
4 + (16*2.0%) = 4.32 mA
3.5%
20 L/min
800 L/min (800-20)*3.5% + 20 = 27.3 L/min 4 + (16*3.5%) = 4.56 mA
3.5% up-side-down
800 L/min 20 L/min
(800-20)*3.5% + 20 = 27.3 L/min 20 - (16*3.5%) = 19.44 mA
