Configuration; Cable Shield; Pulse Output - Seametrics AG90 Series Manual

CONFIGURATION

Cable Shield. In general, the cable shield and its bare drain
wire should be left unconnected at the user equipment end
of the cable to minimize "ground loop" problems.
Pulse Output Configuration. A pulse output is standard
on all models. Since this is an isolated output, the external
equipment must include a DC power source to regenerate
the pulse from the open-collector output (transistor
equivalent of a contact closure).
down resistor may be needed if not included in the user
equipment. Both the power source and resistor may be
supplied internally in some types of control and monitoring
devices. If not, as for most PLC discrete input modules, they
must be added externally at the module input terminals.
The pulse output rate in volume units/pulse can be set by
the user via the SETP tab on the meter's setup menus.
Because the pulse output of an AG90 meter is set by the
user, care must be taken to assure the output pulses do not
exceed the maximum frequency of the meter while also
ensuring a reasonable resolution.
K-factor: Remember that SETP is expressed in units totaled
per output pulse (G/P if using gallons) while K-factors
are expressed in pulses per gallon (P/G.) To determine
K-factor from SETP, divide 1 by SETP (if SETP is expressed in
gallons.) Conversely, 1 divided by the K-factor equals SETP
AG90 battery powered units have a maximum output
frequency of 150 Hz.
Pulse Units. The units of measure of SETP are independently
selectable and are not tied to rate or total. Upon change of the
SETP unit, the pulse output may take up to 10 seconds, or the
duration of one pulse (whichever is longer) to take effect.
If Pulse Output is Inconsistent. The DAMP filter may need
to be increased.
Pulse Width Timing. The unit and value of SETP must be
chosen to keep the duration between meter pulse outputs to
less than 500 seconds.
Pulse Timing in Battery Powered Units. The output pulse
width in battery powered units is short and varies with pulse
frequency. (See table)
Seametrics • 253.872.0284
Because all pulse outputs (SETP) are configured in (rate)
units totaled per pulse, all sizes of meters can be configured
with the same SETP values
For example, if your rate is chosen as gallons per minute
(GPM) the table below applies. If your rate is different,
simply use your rate label in place of (GPM.) The numerical
values will remain the same.
A pull-up or pull-
Lower frequency output pulses (1 pulse for some particular
number of gallons) can also be set.
Any output frequency can be determined by:
Output Pulse Frequency
Example: If frequency = 20 Hz then the pulse period = 50 milliseconds and pulse
width = (.05 x 50 milliseconds) = 2.5 ms
Page 12
AG90 - SERIES INSTRUCTIONS
Flow Rate at 1 Hz
SETP (GPM)
0.1 6
0.2 12
0.3 18
0.4 24
0.5 30
0.6 36
0.7 42
0.8 48
0.9 54
1.0 60
Rate (units/minute) ÷ SETP (units/pulse) = pulse/minute
Hz = pulse/minute ÷ 60 seconds / minutes
Output Pulse Width of Battery Powered Units
Output Pulse Width as a Percentage of
(Pulse period = 1000 milliseconds/fre-
Multiply the pulse
Zero to 1 Hz
period by 0.01
Multiply the pulse
>1 to 20 Hz
period by 0.05
Multiply the pulse
>20 to 100 Hz
period by 0.1
Multiply the pulse
>100 to 150 Hz
period by 0.15
Flow Rate at 150 Hz
(GPM) Battery Powered
Meters
900
1800
2700
3600
4500
5400
6300
7200
8100
9000
the Pulse Period
quency)
= Output Pulse
Width (ms)
= Output Pulse
Width (ms)
= Output Pulse
Width (ms)
= Output Pulse
Width (ms)
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