Seametrics iMAG Instructions Manual Download

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INPUTS/OUTPUTS and OPERATION

Battery Power.

The iMAG 4600 meter can come configured

with  two  replaceable  3.6V  lithium  ‘D’  batteries.    In  this
configuration,  the  only  option/output  is  the  scaled  pulse
output which comes standard.  The scaled output for the
battery powered option has a maximum frequency of 10Hz,
with a fixed pulse width of 10ms.  Be sure to set your P value
such that the meter will function properly over the flow range
in your application.

See the tech bulletin on this topic for

more details.

The sample rate of the meter is user selectable

through the SAMP tab in the meter’s sub-menu.  Sample
periods of  0.2, 0.33, 1, 3, 5, 15, 30, and 60 seconds can
be selected.  Larger sample periods will yield longer battery
life but slower response time.  Care must be taken to select
a sample period that us suitable for your application.  See
the table on the next page for the expected battery life as a
function of sample period.

Pulse Output Connection.

When the second OID code

character is “P”, refer to the “

Digital Output Application”

diagrams  on  page  12  for  recommended  pulse  output
connections to external equipment. 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).  A pull-up
or pull-down resistor may be needed if not included in the
user equipment as shown in the diagrams. 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. Pulse output rate in volume
units/pulse is user-settable via the SET P tab on the meter’s
setup menus.

Analog Output (4-20mA) Connection.

When the second or

third OID code character is “L” or “H”, refer to the “

Analog

Output Application”

diagram on page 12 for 4-20mA current

loop output connections to external analog input devices.
Since the meter’s analog output is isolated and passive, loop
power must be supplied externally as shown. (In addition, an
external resistor R

will be needed to convert the loop current

to voltage for voltage-only input devices.) The meter’s loop
transmitter minimum voltage drop is 6Vdc (8Vdc with HART)
which, with wiring resistance and loop power supply voltage,
will determine the maximum resistance for R

. The flow rates

corresponding to 4 and 20mA are user-settable via the SET
4 and SET20 tabs on the meter’s setup menus.

(Optional) Setup and Connection to a HART Network.

The

HART protocol, rev.7.5, allows for a Polling address of 0-63.
The default value in the iMAG is 0. To change the Polling
address, use iMAG menu HPOLL to set the Polling address.

To get to this menu, move to the EXIT tab and tap the

Hold

Tap

4 times. This will bring up another menu page
containing the tab HPOLL. Use the

Hold

Tap

to select the

Polling address.

A minimum of 250 ohms of loop resisitance must be present
in order for the HART modem to correctly and reliably
demodulate FSK voltage. With this in mind, the maximum loop
resistance* for the iMAG HART interface cannot be exceeded
in order to assure correct operation.

Use of HART Communicator.

The iMAG HART interface is

HART compatible.  All the commands have been implemented
in accordance with the HART Protocol Specification published
by HART Foundation.  A HART Communicator can be used with
the iMAG, even in the absence of DD files, by taking advantage
of the Generic Online Menu capability of a Communicator.
This means that a generic menu is automatically available
when DD files are not present.

The following information from the iMAG HART can be
displayed on the Communicator using the generic menu:

Flowrate in units selected for iMAG

PV Loop Current

Loop current in mA

PV LRV

Lower range value of PV in units

selected for iMAG

PV URV

Upper range of PV in units selected for

iMAG

*4-20 mA loop has maximum loop resistance of 650ohms
and requires a 24Vdc power supply.

Battery Life/Sample Period