37
TROUBLESHOOTING
Display does not come on or is weak.
Check power and ground connections. Please reference the technical specifications
(pages 41-44) to assure you have the proper power for your model.
Flow reading is approximately fixed either near zero or near full scale regardless
of actual line flow.
Differential pressure sensor may be damaged. Avoid installations that can subject
the sensor to excessive pressure differentials (see page 7). A common cause of this
problem is instantaneous application of high-pressure gas as
from a snap acting solenoid valve upstream of the meter. If you suspect that your
pressure sensor is damaged please discontinue use of the meter and contact
MATHESON.
Displayed mass flow, volumetric flow, pressure or temperature is flashing and
message MOV, VOV, POV or TOV is displayed:
Our flow meters and controllers display an error message (MOV = mass overrange,
VOV = volumetric overrange, POV = pressure overrange, TOV = temperature
overrange) when a measured parameter exceeds the range of the sensors in the
device. When any item flashes on the display, neither the flashing parameter nor
the mass flow measurement is accurate. Reducing the value of the flashing
parameter to within specified limits will return the unit to normal operation and
accuracy. If the unit does not return to normal contact MATHESON.
Meter reads negative flow when there is a confirmed no flow condition.
This is an indication of an improper tare. If the meter is tared while there is flow,
that flow is accepted as zero flow. When an actual zero flow condition exists, the
meter will read a negative flow. Simply re-tare at the confirmed zero flow
condition. Also note that while the meter is intended for positive flow, it will read
negative flow with reasonable accuracy, but not to the full scale flow rate and no
damage will result.
Meter does not agree with another meter I have in line.
Volumetric meters are affected by pressure drops. Volumetric flow meters should
not be compared to mass flow meters. Mass flow meters can be compared against
one another provided there are no leaks between the two meters and they are set
to the same standard temperature and pressure. Both meters must also be
calibrated (or set) for the gas being measured. 819-Series mass flow meters are
normally set to Standard Temperature and Pressure conditions of 25° C and 14.696
psia. Note: it is possible to special order meters with a customer specified set of
standard conditions. The calibration sheet provided with each meter lists its
standard conditions.
When performing this comparison it is best to use the smallest transition possible
between the two devices. Using small transitions will minimize lag and dead
volume.
Summary of Contents for 819 Series
Page 46: ...46 Notes...
Page 47: ...Notes 47...
