User manual - FLOW METER SPI-638
6.
PRINCIPLE OF OPERATION
After turning the power supply on, device ID and software version are showed on the
display, next the controller goes to the measurement mode.
6.1.
MEASUREMENT MODE
In the measure mode, device displays instantaneous measurement (flow value or time
per one unit of flow, depending on „
F or P
” parameter value) equivalent to quantity of input
pulses, total flow or batcher counter value.
Displayed value presentation is defined by parameters
“F unit”
,
“t unit”
and
“b unit”
with resolution defined by parameters
“F PrEc”
,
“t PrEc”
and
“b PrEc”
.
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“F unit” “F PrEc”
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“F unit” “F PrEc”
Instantaneous flow (flow rate) is displayed in units defined by parameter
“F unit”
and
“Ftunit”
(min., sec. or h), with resolution defined by
“F PrEc”
(max. 5 digits after decimal
point). Pulses delivered to device's input (Figure 4.13) are recalculated according with
procedure showed below:
•
if duration of low or high level (between pulses) is lower than time defined by parameter
“FrEq”
(see Tab.7.1 page 33), these pulses are recognized as noise (or bouncing) and will
be ignored
•
if duration of both levels are in acceptable range, but input frequency is higher than defined
by parameter
“FrEq”
, device goes to alarming state - relays and current output are
switched to their alarm states defined by parameters
“ALArmS”
of particular menus. In
alarm state flow counter displays
”-Hi-”
message, in place of flow result.
•
In all other cases (while frequency and pulses duty cycle gets acceptable values) input
pulses are delivered to internal prescaler. The prescaler (see description of parameter
“PULSEL”
) should be set to value equal to the quantity of pulses per one unit.
Frequency after prescaler is recalculated accordingly to user defined unit (parameters
“F unit”
and
“Ftunit”
), and after that final flow value in units or thousands of units (e.g.
litres or cubic meters) per hour, minute or second is obtained. This result is displayed on
the display and is used to determine states of relays and current output, additionally the
result is accessible via RS 485 interface as a set of holding registers.
–
If input frequency is in acceptable range but result is longer than 6 digits, warning
message
“-Ov-”
is displayed in place of the result. In that case parameters
“
F unit
”
,
“Ftunit”
and
“F PrEc”
should be corrected to obtain proper result.
–
While
time per one unit of flow is displayed
(parameter
“F or P”
= “
PEriod
”):
•
If flow value equals 0, then 0 value is displayed.
•
If value of period is to high to be fitted on 6 digits, message
“-OvLd-”
(Overload) is displayed instead of the result.
•
If flow value is different than 0 but value of period is to small to be fitted on
6 digits, message
“-UnLd-”
(Underload) is displayed instead of the result.
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