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  • The display does not come on or is weak.

    Check power and ground connections.

  • The 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 sensor to pressure drops in excess of 75 psid (15 psid for “Whisper” Series instruments). A common cause of this problem is instantaneous application of high-pressure gas as from a snap acting solenoid valve upstream of the meter. Damage due to excessive pressure differential is not covered by warranty.

  • The 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 (it is not calibrated for bidirectional flow) and no damage will result.

  • The meter does not agree with another meter I have in line.

    Volumetric meters will often not agree with one another when put in series because they 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. M Series mass flow meters are normally set to Standard Temperature and Pressure conditions of 25° C and 14.695 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.

  • The 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: Meters feature a programmable geometric running average (GRA) that can aid in allowing a rapidly fluctuating flow to be read.

  • 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.

  • My volumetric meter reading is strange, inconsistent, or incorrect.

    Make sure you use a volumetric flow meter only under low pressure (close to atmospheric) and with little to no back pressure for accurate readings. Mass meters should be used for higher pressure applications.

  • The RS-232 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.

  • The device is responding slower than specified.

    Meters feature an RS-232 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. If you require the fastest possible response time, please consult the factory for written instructions on adjusting the GRA.

  • The device jumps to zero at low flow.

    Meters feature an RS-232 programmable zero deadband. The factory setting is usually 0.5% of full scale. This can be adjusted via RS-232 programming between NONE and 6.375% of full scale. Contact the factory for more information.