Alicat P Series Pressure Gauge User Manual
Page 37
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Changing From Streaming to Polling Mode:
When the meter is in the Streaming Mode (RS-485 units do not have a
streaming mode), the screen is updated approximately 10-60 times per second
(depending on the amount of data on each line) so that the user sees the data
essentially in real time. It is sometimes desirable, and necessary when using
more than one unit on a single RS-232 line, to be able to poll the unit.
In Polling Mode the unit measures the flow normally, but only sends a line of
data when it is “polled”. Each unit can be given its own unique identifier or
address. Unless otherwise specified each unit is shipped with a default address
of capital A. Other valid addresses are B thru Z.
Once you have established communication with the unit and have a stream of
information filling your screen:
1. Type *@=A followed by “Enter” (or using the RS-232 / RS-485
communication select menu, select A as identifier and exit the screen) to
stop the streaming mode of information. Note that the flow of information
will not stop while you are typing and you will not be able to read what you
have typed. Also, the unit does not accept a backspace or delete in the line
so it must be typed correctly. If in doubt, simply hit enter and start again. If
the unit does not get exactly what it is expecting, it will ignore it. If the line
has been typed correctly, the data will stop.
2. You may now poll the unit by typing A followed by “Enter”. This does an
instantaneous poll of unit A and returns the values once. You may type A
“Enter” as many times as you like. Alternately you could resume streaming
mode by typing *@=@ followed by “Enter”. Repeat step 1 to remove the
unit from the streaming mode.
3. To assign the unit a new address, type *@=New Address, e.g. *@=B. Care
should be taken not to assign an address to a unit if more than one unit
is on the RS-232 / RS-485 line as all of the addresses will be reassigned.
Instead, each should be individually attached to the RS-232 / RS-485 line,
given an address, and taken off. After each unit has been given a unique
address, they can all be put back on the same line and polled individually.