Xylem FM500 ULTRASONIC FLOW METERS - Manual (Page 24)

Page 24
If the Transit Time measurement mode is selected, a zero calibration should be
performed if possible.
There must be no
movement of fluid in the pipe. Do not perform zero calibration if it is not possible to
establish zero fluid flow in the pipe. If there is flow during zero calibration, then flow
measurement in Run Mode will be inaccurate. The only means provided to cancel zero
calibration or to undo its effect is to perform another zero calibration.
Zero calibration must be started while in the Startup State by holding down the SETUP
button for at least 3 seconds. The Startup State may be entered by power cycling the
flowmeter or upon exit from the Setup Mode or Transducer Positioning state. With either
the Model S3 display or the optional Communications Board and a connected Host PC,
the Setup Mode can be activated directly from the Run Mode by pressing the SETUP
button and then the pressing the ESC button.
There must be no movement of fluid in the pipe during the
calibration. It is not necessary to perform zero calibration if Doppler measurement mode
is selected, however it is harmless and will have no effect on the measurement.
In the Zero Calibration State, the flowmeter measures and records the apparent rate of
fluid flow to offset measurements in Run Mode and compensate for any zero flow error.
This information is associated and stored with the active Configuration Set and survives
power loss and restarts. If a new Configuration Set is made activate, it will have its own
zero calibration information. Therefore, the calibration must be performed after the
configuration is created and saved. Although the zero calibration is not required, positive
or negative zero offset reading error may result if the calibration is not performed.
The approximate duration of zero calibration is 15 to 20 seconds.
On completion of zero calibration, the flowmeter returns to the Startup State and will
again wait for up to 7 seconds for the Setup button to be pressed.
The flowmeter indicates that it is in the Zero Calibration State as follows:
Model 1: one yellow LED flashes at 1 Hz
Model 2: as for Model 1, plus the display
screen indicates:
Zero Calibration ...
Below this, a “progress bar” counts off the
15 to 20 second delay.
Model 3: as for Model 2.
INDICATOR LIGHTS DURING
ZERO FLOW CALIBRATION
MODEL 2 and MODEL 3
4.6
Zero
Calibration
State
Zero Calibration …
£ £ £ £ ¢ ¢ ¢ ]
Information Screen
Firmware Version, B01.00.00
¢ ¢ ¢ [£ £ £
Ultrasonic Flowmeter