= 154.42
Frequency Setting Example
An IP 81 with AO55M is installed in a 2" PVC line.
The maximum flow for this installation is estimated
to be about 150 GPM.To be on the safe side, a flow
rate of 170 GPM is selected as the full-scale
maximum, the flow at which the current loop will
register 20 mA.
The model/serial label on the SeaMetrics fitting
reads "k = 54.50"
2 of 4
Installation
Mounting.The wall mount style (AO55W) is the only
housing which needs to be mounted, since the meter
mount (AO55M) is already physically connected to the
flowsensor.The AO55W comeswithmounting feet and
requires four screws to attach it to any stable surface.
Connection. On either style of housing, the upper
portion must be removed to make connections.Use a
standard hex wrench (5/32" or 4 mm) to loosen the
screws, then remove the upper half.The connections
are made to terminal blocks in this upper half, which
contains the potted electronics.Note that the terminal
blocks are a removable style, and can be unplugged
and plugged back in for convenience.
Look at the connections diagram before connecting to
the current loop.The only connections required on an
AO55Marethe positiveandnegative loop connections.
On an AO55W, the sensor must also be connected,
since it is remote from the transmitter.Be careful to
follow the color coding of the three flow sensor wires in
order to establish the correct polarity.Incorrect polarity
can damage the sensor.
Settings
Setting Frequency.The AO55 converts a train of off/
on pulses from the flow sensor into a continuous
milliamp signal.This signal ranges from 4 milliamps at
zero flow to 20 milliamps at the desired maximum flow.
This desired maximum is determined by the user, and
then entered as a frequency.
Todetermine the frequency setting, follow these steps:
1) Decide what flow rate should represent the top of
thescale.This isordinarilythe maximumexpected flow
or a value just above it, in gallons per minute.
2) Determine the k-factor of the flow sensor.This will
be on the model/serial label of the fitting in the case of
anyTX or IP 80-series (81 or 82).For an IP or TX 100/
200 series (101, 201, 115, 215) it will be on a chart in
the instruction manual.For any S-series flow sensor
(SPX, SPT, SEB) it will be on the model/serial label.
The k-factor is simply the number of pulses the flow
sensor produces per gallon of flow.It is determined by
a flow test, except in the case of the 100/200 series,
which are adjustable for a wide range of pipe sizes.
3) Calculate frequency, using this formula:
K-FACTOR X TOP FLOW (GPM)
60
Enter this frequency,using the four rotary switches
marked frequency.Note the decimal point between the
third and fourth switches.
Example: 154.4
Turn rotary switch pointer to the desired digit.
0
9
8
7
6
5
4
3
2
1
0
9
8
7
6
5
4
3
2
1
0
9
8
7
6
5
4
3
2
1
0
9
8
7
6
5
4
3
2
1
AO55
Frequency
Power
Sensor
4-20 mA
154.4
Rounding to one decimal point, 154.4 is entered on
the rotary switches (154.4).
54.50 x 170
60
