Alicat V Series Volumetric Flow Meter User Manual

Page 20

In Polling Mode, the screen should be blank except the blinking cursor. In order to get the data streaming

to the screen, hit the “Enter” key several times to clear any extraneous information. Type “*@=@”

followed by “Enter” (or using the RS-232 communcation select menu, select @ as identifier and exit the

screen). If data still does not appear, check all the connections and com port assignments.

Changing From Streaming to Polling Mode:

When the meter is in the 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:

Type *@=A followed by “Enter” (or using the RS-232 communcation 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.
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.
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 RS232 line as all of the addresses will be

reassigned. Instead, each should be individually attached to the RS-232 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.

Tare –Tareing (or zeroing) the flow meter provides it with a reference point for zero flow. This is a simple

but important step in obtaining accurate measurements. It is good practice to “zero” the flow meter each

time it is powered up. A unit may be Tared by following the instructions on page 10 or it may be Tared

via RS-232 input.
To send a Tare command via RS-232, enter the following strings:
In Streaming Mode: $$V
In Polling Mode:

Address$$V (e.g. B$$V)