Instructions for Use
– SCHMIDT
®
Flow Sensor SS 20.500
Page 29
7 Information concerning operation
Ambient condition temperature
The
SCHMIDT
®
Flow Sensor SS 20.500
monitors the temperature of both
medium and electronics. As soon as one limit of the specified temperature
ranges is exceeded, the sensor switches off one or both measuring func-
tions associated with the medium depending on the situation and report
the corresponding error. As soon as proper operational conditions are re-
stored, the sensor resumes normal function.
Even a short-term overshooting of the safety limit values can lead to per-
manent damage of the sensor which must be avoided by all means. On
the other hand, falling below is less critical but leads to an increased brit-
tleness of sensitive components, for example of the sensor tip or connect-
ing cable.
Even short-term overshooting of operating temperatures can
cause irreversible damage to the sensor.
Ambient condition pressure
The flow sensor
SS 20.500
exhibits a minor dependency on overpressure
p
op
close to zero flow. At w
N
= 0 m/s the sensor signals with increasing
overpressure an increasing flow w
N,Sensor,0,Op
> 0 m/s in a proportional way.
This deviation decreases rapidly with increasing flow and diminishes at
w
N,Sensor,C
showing correct measurements with no further influence from
pressure (see Table 8).
The residual dependence of the pressure can be calculated to:
𝑤
𝑁,𝑆𝑒𝑛𝑠𝑜𝑟,0,𝑂𝑝
= 0.04
𝑚
𝑠
⁄
𝑏𝑎𝑟
∙ 𝑝
𝑂𝑃
𝑤
𝑁,𝑆𝑒𝑛𝑠𝑜𝑟,𝐶
= 2 ∙ 𝑤
𝑁,𝑆𝑒𝑛𝑠𝑜𝑟,0,𝑂𝑝
Table 8 Dependence of sensor signal near zero flow
!
p
Op
[bar]
0,0
0,1
0,2
0,3
0,4
0,6
0,8
1,0
0
0,00
0,00
0,20
0,30
0,40
0,60
0,8
1,0
2
0,08
0,09
0,20
0,30
0,40
0,60
0,8
1,0
4
0,16
0,18
0,26
0,31
0,40
0,60
0,8
1,0
6
0,24
0,26
0,34
0,39
0,44
0,60
0,8
1,0
8
0,32
0,35
0,42
0,47
0,52
0,62
0,8
1,0
10
0,40
0,44
0,50
0,55
0,60
0,70
0,8
1,0
Sensor signal: w
N,Sensor
[m/s]
@ w
N
[m/s]
