Different Kinds Of Measuring; Water Depth / Level Measurement; Sea-Level Correction For Absolute Pressure Sensors - GREISINGER GMH 5155 Betriebsanleitung

H82.0.03.6C-08

7.2 Different kinds of measuring

Three different kinds of pressure measuring are supported. Two of them (P.dEt and FASt) are working with
high measuring frequency of more than 1000 measurings per second.
7.2.1 Standard measuring (slow)
Measuring rate 4 Hz, averaging and filter functions are active.
Application: Measuring of slowly changing or static pressures, e.g. measuring of leakproofness,
atmospheric pressure...
Highest accuracy, high noise immunity, low power consumption.
7.2.2 Peak detection (Peak detection)
Measuring rate >1000 Hz, the value is displayed unfiltered.
Application with logger function: Measuring of short pressure peaks or fast changing pressures with
a resolution of <1 ms. The cyclic logger function records the arithmetic mean value, the highest and
the lowest peak of the referring time interval.
Attention: higher power consumption, measuring is sensitive to noise (EMI, ...).
Measuring is sensitive to noise (EMI, ...)
and higher power consumption.
7.2.3 Fast filtered measuring (fast)
Measuring rate >1000 Hz, but the value is filtered (higher noise immunity than P.dEt, small peaks
will be filtered out), apart from that identical behavior like rAtE-P.dEt.

7.3 Water depth / level measurement


Water-proof sensors have to be used for water depth / level measurement.
Select the unit [m] for meters water column (selection mH2O) in menu "Unit".10 m water column (=water
depth) corresponds roughly 1 bar overpressure.
Measurings can be made e.g. like described below:
With one abs. pressure sensor: Press „Tara‟ when sensor is at ambient air and then bring sensor to the
depth to be measured. The display shows now the depth in [m].
With two abs. pressure sensors: Sensor 2 at ambient air (does not have to be waterproof), waterproof
sensor 1 at water depth to be measured. Don‟t press „Tara‟, the depth can already read from the DIF-
display and is compensated for pressure changes in ambient air.
With one rel. pressure sensor: bring tube connection for lower press. in contact to ambient air by means
of a tube (no water contact!) and bring the sensor with its open pressure connection for higher pressure
to water depth to be measured (display and is compensated for pressure changes in ambient air).

7.4 Sea-level correction for absolute pressure sensors

The device displays the absolute pressure. This is not necessarily the same like the values given by weather
stations! The weather stations are displaying the pressure at sea level. Usually the sensor is placed above
sea level and therefore the pressure loss resulting from the actual level above sea level has to be
considered, if the value at sea level (zero) should be measured! To correct the measuring display, activate
the "Sea-Level-Function" (SL, p.r.t. chapter 6, setting is only possible, if an abs. pressure sensor is
connected to sensor connection 1). Then enter the altitude above sea level of the sensor‟s location in meters
(Alti, p.r.t. chapter 6). When activated, the display shows the SL-arrow and the device displays the pressure
value at sea level.
When two absolute pressure sensors are connected, the sea level function for both corresponds to
the setting of sensor 1.
Operating Manual GMH 5155
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(for abs. pressure sensors SL has to be deactivated)
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