Yamatake Corporation
5-8
ST3000 Smart Transmitter Series 900 Electronic Differential Pressure/Pressure Transmitter
Sealed liquid temperature correction function
When the liquid level of a tank is measured using a remote sealing type differential
pressure transmitter, the density of the sealed liquid in the capillary tube changes as
the ambient temperature changes. This ordinarily causes about 4~5% zero shifting.
The STR/STE has a composite semiconductor sensor with a function for correcting
sealed liquid temperature by means of temperature measurement and arithmetic opera-
tion with a microprocessor. This assures accurate level measurements. (The zero shift
is reduced to 1/5 from the previous level.)
Example of zero shift
L (Difference between flanges): 2500 mm (2.5 m)
R (Measurement span): 2500 mm (2.5 m)
A (Temperature coefficient of sealed liquid):0.001/
°C
T (Ambient temperature change): 55°C
Zero shift
...
(1)
From (1)
Zero shift of a model without temperature correction:
%
(Conventional transmitter)
Zero shift of a model with temperature correction
function DSTJ3000: 1%
A T L
×
×
R
---------------------- 100
×
=
0.001 55 2500
×
×
2500
-------------------------------------------- 100
×
5.5
=
