Digital Paddlewheel flowmeter

Principles of Operation
Fluid flowing through the unit causes the digital paddle wheel to spin. As the magnets embedded in the paddle spin past the sensor, electrical pulses are produced in which frequency is proportional to the flow rate. The number of pulses per desired time interval and the K-factor (number of pulses/Gallon) make it is possible to calculate the flow rate and volume passing through the unit.

On board CPU and signal conditioner circuitry perform accurate flow and total computation, digital communication and analog 0-5 Vdc or 4-20 mA output signals. Non-volatile memory stores all hardware specific and user programmable variables, including flow linearization table.

The flow rate can be displayed in 29 different volumetric or mass flow engineering units. Flow meter parameters and functions can be programmed locally via optional key pad and LCD† or remotely via the RS-232/RS-485 interface.
PWE flow meters support various functions including: two independently programmable flow totalizers, user programmable low, high or range flow and temperature alarm, two sets of user programmable optically isolated outputs, self diagnostic alarm, flow pulse output.

Optional local 2x16 LCD† readout with adjustable back light provides flow rate, temperature†, total volume reading in currently selected engineering units, diagnostic events indication and feature a password protected access to the process parameters to ensure against tampering or resetting.
(† - optional feature)

Totalizer
The total volume of the liquid is calculated by integrating the actual liquid flow rate with respect to time. The optional LCD/keypad 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. Main Totalizer reading
is stored in the non volatile memory (EEPROM). The pilot Totalizer reading is stored in volatile memory (SRAM) and will be lost if flow meter is powered down.

Design Features

  •  Supports up to 29 Engineering Units (including User Defined).
  •  Two programmable Totalizers (main and pilot) indicate total liquid volume.
  •  Programmable High and Low Flow Alarm limits with preset delay interval.
  •  Programmable High and Low Temperature Alarm limits with preset delay interval (optional).
  •  Two sets of user-programmable optically isolated outputs.
  •  User-selectable (via jumpers) analog 0-5 Vdc or 4-20mA flow and optional temperature outputs.
  •  Flow Pulse output (3.3Vdc CMOS).
  •  Digital Interface (RS-232 or RS-485).
  •  Multi-Drop Capability of up to 256 units (RS-485 option).
  •  Extensive Self Diagnostics with LCD (optional) indication.
  •  Local key pad and 2x16 characters LCD display with adjustable back light (optional).
  •  Enclosure weather tight to IP65 standards.
  •  Free communication software with temperature and flow data log-in capability.

Flow and Temperature Alarms
High and Low flow ALARM limits can be preprogrammed via digital interface or optional LCD/Keypad. ALARM conditions become true
when the current reading is equal or higher/lower than corresponding values of high and low alarm levels. Alarm action can be assigned with preset delay interval (0-3600seconds) to activate the optically isolated output (separate for High and Low alarm). Latch Mode control feature allows each optical output to be latched on or follow the corresponding alarm status.

Optically Isolated Outputs
Two sets of optically isolated outputs are provided to actuate user supplied equipment. These are programmable via digital interface or optional LCD/Keypad such that the outputs can be made to switch when a specified event occurs (e.g. when a low or high flow alarm limit is exceeded or when the totalizer reaches a specified value) or may be directly controlled by user.

 


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