Calibration
Page 21
© 2016 Valeport Ltd
6.1. Adjusting Zero Offset
In the event that the zero offset requires adjusting from the factory set calibration, this can be
done by the user using the following procedure.
6.1.1. Determining the Updated Offset
6.1.1.1. Method 1 - Using Data Displayed at Zero Flow
Note the zero reading [Zr] in still water in mm/sec [note the display reading is in M/sec]. Great
care should be taken to ensure that the water is still.
From the calibration sheet, note the zero offset figure [in counts] defined for the unit [Zc1]. This
figure can also be read from the unit by the #172<cr> command [see above].
Calculate the new zero offset counts, Zc2 from the equation:
Zc2 = Zc1 - (Zr * (Counts per mm/sec))
The calibration is approximately 1mm/sec is 1 count, so the equation becomes:
Zc2
=
Zc1 – (Zr * (Counts per mm\sec))
For example:
Original zero offset in counts,
Zc1
=
- 6.45
Zero reading in still water,
Zr
=
- 0.005 m/sec
=
- 5 mm/sec
New zero offset in counts,
Zc2
=
- 6.45 – (-5)
=
- 6.45 + 5
=
- 1.45 counts
Note that it is important to use the correct signs
