DFM Digital Mass Flowmeter

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Design Features

  • Multi-drop Capability of up to 256 units (for RS-485 option)
  • Stores calibration data for up to 10 different gases
  • Supports 10 different engineering units including user defined
  • Programmable 12 digits totalizer indicates total gas volume
  • Flow alarm limits for high and low gas flow with relay output
  • Pressure alarm limits for high and low gas pressure with relay output
  • Temperature alarm limits for high and low gas temperature with relay output
  • Four button keypad and large 128×64 graphical LCD with back light
  • Digital (RS-232 or RS-485) and analog outputs operate simultaneously
  • Internal conversion factors for up to 32 gases
  • Automatic zero adjustment
  • Self diagnostic tests

Description

DFM digital mass flow meter
Interface
All features of the flow meter can be accessed via the local four button keypad and LCD. The digital interface operates via RS485 (optional RS-232 available) and provides access to applicable internal data including: flow, temperature, pressure reading, auto zero, totalizer and alarms settings, gas table, conversion factors and engineering units selection, dynamic response compensation and linearization table adjustment.

The analog interface provides 0 to 5Vdc or 0 to 10Vdc or 4 to 20 mA outputs for flow, pressure and temperature (jumper selectable).

Auto Zero
The DFM supports automatic sensor zero offset adjustment which can be activated locally via keypad or remotely via digital interface. The auto zero feature requires absolutely no flow through the meter during auto zero process. Provisions are made to either start, stop or save the current auto zero value via digital commands.

Totalizer
The total volume of the gas is calculated by integrating the actual gas flow rate with respect to time. Both keypad menu and digital interface commands are provided to:
set the totalizer to ZERO
start the totalizer at a preset flow
assign action at a preset total volume
start/stop totalizing the flow
read totalizer
Totalizer conditions become true, when the totalizer reading and the “Stop at Total” volumes are equal.

Flow Alarm
High and Low gas flow ALARM limits can be preprogrammed via keypad or remotely via digital interface. ALARM conditions become true when the current flow reading is equal or higher/lower than corresponding values of high and low alarm levels. Alarm action can be assigned with preset delay interval (0-3600 seconds) to activate the contact closer (separate for High and Low alarm).

Pressure Alarm
High and Low gas pressure ALARM limits can be preprogrammed via keypad or remotely via digital interface. Pressure alarm conditions become true when the current pressure reading is equal or higher than corresponding values of high pressure alarm settings or equal or lower than corresponding values of low pressure alarm settings. Alarm action can be assigned to activate the contact closer (separate for High and Low pressure alarm).

Temperature Alarm
High and Low gas temperature ALARM limits can be preprogrammed via keypad or remotely via digital interface. Temperature alarm conditions become true when the current temperature reading is equal or higher than corresponding values of high temperature alarm settings or equal or lower than corresponding values of low temperature alarm settings. Alarm action can be assigned to activate the contact closer (separate for High and Low temperature alarm).

Engineering Units
The flow set points, measured gas flow and associated totalizer data are scaled directly in engineering units via the front panel keypad or digital interface.

The following units of measure are supported: %F.S., L/min, L/h, mL/min, mL/h, SCFH, SCFM, LbPH, LbPM, User Defined EU.

Multi-Gas Calibration
The DFM is capable of storing primary calibration data for up to 10 gases. This feature allows the same DFM to be calibrated for multiple gases while maintaining the rated accuracy on each.

Conversion Factors
Conversion factors for up to 32 gases are stored in the DFM. In addition the provision is made for a user defined conversion factor. Conversion factors may be applied to any of the ten gas calibrations via keypad or digital interface commands.

Contact Closure
Two sets of dry contact relay outputs are provided to actuate user supplied equipment. These are programmable via local keypad or digital interface such that the relays can be made to switch when a specified event occurs (e.g. when a low or high flow, pressure or temperature alarm limit is exceeded or when the totalizer reaches a specified value).

Leak Integrity
1 x 10-9 sccs of Helium maximum to the outside environment.