Alicat M Series Mass Flow Meter - Manual (Page 33)

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Flow flutters or is jumpy.
The meters are very fast and will pick up any actual flow fluctuations such as from a
diaphragm pump, etc. Also, inspect the inside of the upstream connection for debris
such a Teflon tape shreds.
Note: M-Series meters feature a programmable geometric running average (GRA) that
can aid in allowing a rapidly fluctuating flow to be read (see “Pressure Averaging” and
“Flow Averaging” page 20).
The output signal is lower than the reading at the display.
This can occur if the output signal is measured some distance from the meter,
as voltage drops in the wires increase with distance. Using heavier gauge wires,
especially in the ground wire, can reduce this effect.
RS-232 / RS-485 Serial Communications is not responding.
Check that your meter is powered and connected properly. Be sure that the
port on the computer to which the meter is connected is active. Confirm that
the port settings are correct per the RS-232 instructions in this manual (Check
the RS-232 / RS-485 communications select screen for current meter readings).
Close Hyperterminal® and reopen it. Reboot your PC. See pages 10, 11 and 22
for more information on RS-232 / RS-485 signals and communications.
Slower response than specified.
M-Series Meters feature a programmable Geometric Running Average
(GRA). Depending on the full scale range of the meter, it may have the GRA
set to enhance the stability/readability of the display, which would result in
slower perceived response time. Please see “Pressure Averaging” and “Flow
Averaging” on page 20.
Jumps to zero at low flow.
M-Series Meters feature a programmable zero deadband. The factory setting is
usually 0.5% of full scale. This can be adjusted between NONE and 3.2% of full
scale. See page 20.
Discrepancies between old and new units.
Please see “Standard Gas Data Tables” explanation on page 29.