Example: display in hl
display for p
zero
≠ 0
Calculate the pressure in mbar acting at the sensor for the desired »empty« level and
the span (»full« - »empty«):
p
mbar
= 10 x ρ (kg/dm
3
) x g (m/s
2
) x ∆h (m)
For 0.0 m water, display = 50 hl
For 10.0 m water, display = 2000 hl
Span (50
…
2000 = 1950) = 10 m
• p
zero =
10 x 1.0 x 9.807 x 0.0 = 0.0 mbar
p
1950 =
p
span
= 10 x 1.0 x 9.807 x 10.00 = 980.7 mbar
• Offset = p
zero
= = 0.0 mbar
Sensitivity = p
span
/span = 980.7/1950 = 0.5029 mbar/hl
Sensor calibration
# Matrix Entry Remarks
1 V0H2 e.g. 2000 Full level (100%)
2 - »E« Register entry
3 V3H1 0.0 Offset in mbar
4 - »E« Register entry
5 V3H2 e.g. .5029 Sensitivity mbar/hl
6 - »E« Register entry
The Prolevel now measures 0 at 0 mbar — a
negative level offset must be entered, p. 25
7 V3H4 e.g. -50 Level offset
8 - »E« Register entry
Next step…Set analogue outputs and relays in the units used for calibration, e.g. hl, see p. 30…33.
Density correction for
hydrostatic sensor
If the product changes after calibration, the measurement can be corrected by entering
a density factor at V8H7:
Factor = old factor x new density
old density
The measured value is divided by the factor before display.
Note!
• For an automatic density correction using an additional external limit switch see
»Calibration Correction« in Chapter 5
Note!
VH
00
VH
00
50
2000
»Empty« = 0.0 m
»Full« e.g. 10 m
p
empty
= ρ x g x 0.0
e.g. = 0 mbar
span = 2000 - 50 = 1950
= e.g. 10 m
BA142_35
negative level offset
sensor zero
point
display
Fig. 4.9:
Parameters for dry calibration, display in hl
Prolevel FMC 661 Chapter 4: Level Measurement
Endress+Hauser 29
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