OTT PLS 500, Operating Instructions Manual

Page: 33 / 56

Command Response
▶
Set/read local gravitational acceleration
aXXG<value>!
aXXG! a<value><CR><LF>
a<value><CR><LF>
Description
Set local gravitational acceleration
Read local gravitational acceleration
a
– sensor address
<value> – b.eeeeee
Value range: 9.780360 … 9.832080 m/s 2
Factory setting = 9.806650 m/s 2
The gravitational acceleration at the earth’s surface varies
between 9.78036 m/s
2
at the equator and 9.83208 m/s
2
at
the poles. Also, it decreases by 0.003086 m/s 2 for each
kilometer of elevation above sea level.
Formula for the local gravitational acceleration "g" in m/s
2
:
g = 9.780356 (1 + 0.0052885 sin
2
α
– 0.0000059
sin
2
2
α –
0.003086 h
α
latitude; h height above sea level in km
(Reference: Jursa, A.S., Ed., Handbook of Geophysics and
the Space Environment, 4th ed., Air Force Geophysics
Labora tory, 1985, pp. 14-17).
Example
Local gravitational acceleration in Kempten (Germany): At a
height above sea level of 669 m and a latitude of 47.71° ,
a local gravitational acceleration of 9.80659 m/s
2
results.
Note
The OTT PLS 500 is preset to an average value for Germany
(Kassel). The measured value deviation caused by gravitation-
al acceleration is ±3 mm in Germany (Flensburg – Oberst-
dorf). This measurement error is compensated by inputting the
local gravitational acceleration.
▶
Set/read salinity
aXXS<value>!
aXXS! a<value><CR><LF>
a<value><CR><LF>
Set salinity
Read salinity
a
– sensor address
<value>
–
bbbb.eee
Value range: 0 … 500000 g/l
Factory setting = 0 g/l
Using this command, you can set the salinity at your station
during the level/depth measurement. This is useful, for
example, for stations with increased salinity. Alternatively, it
is also possible to set the average water density.
▶
Set/read average water density
aXXR<value>!
aXXR! a<value><CR><LF>
a<value><CR><LF>
Set average water density
Read average water density
a
– sensor address
<value>
–
b.eeeeee
Value range: 0.500000 … 2.000000 kg/dm
3
Factory setting = 0.999975 kg/dm 3 (at 0 °C)
Using this command, you can set the actual water density at
your station during level/depth measurement. This is useful,
for example, at stations with brackish water. Alternatively, it
is also possible to set the salinity.
33