|
FAQ
- Humidity
Measurement
Which
filter for which application ?
How
often is it necessary to recalibrate E+E humidity transmitters?
Are
the E+E sensors wettable and how do you clean them?
How
fast is the response time of humidity probes?
How
is the long term stability of the E+E sensors in normal environmental
conditions?
|
Which
filter for which application |
|
DUST
FILTER CAPS |
| To
protect the active surface of the humidity sensor from
unwanted pollution, the sensor probes can be fitted with
various dust filter caps, depending on the application. |
|
membrane
filter: for room applications, minor pollution
in HVAC environment,
order code: HA010101 |
|
| response
time: |
20 s |
| size
of pores: |
1
µm |
| suitable
up to: |
80degC |
|
 |
plastic
grid: mechanical protection in clean
atmospheres, very short response times
order code: HA010104 |
|
| response
time: |
5,5
s |
| size
of pores: |
--
µm |
| suitable
up to: |
120degC |
|
 |
sintered
stainless steel filter: for hostile industrial
environment, food applications, mechanical and thermal
stress
order code: HA010103 |
|
| response
time: |
30 s |
| size
of pores: |
10 µm |
| suitable
up to: |
180degC |
|
 |
PTFE
filter: chemical aggressive environment at high
temperatures
order code: HA010105 |
|
| response
time: |
13,5
s |
| size
of pores: |
50
µm |
| suitable
up to: |
180degC |
|
 |
metal
grid filter: high humidity applications, if
there is saturation or quick changing humidity cycles;
order code: HA010106 |
|
| response
time: |
7
s |
| size
of pores: |
100
µm |
| suitable
up to: |
120degC |
|
 |
|
How
often is it necessary to recalibrate E+E humidity
transmitters? |
|
It is
necessary to check the performance of the instruments from
time to time with reference measurements, which show the
steady changes taking place during long periods of time.
According
to work certificates confirming the calibration accuracy
and measurement reliability.
The
calibration interval depends on the
- working range of the
humidity and temperature
- particular application
- pollution
|
|
Recommended
recalibration intervals
first value
for measurement accuracy in the range of ± 2% r.H.
second value for measurement accuracy in the range of ± 5
% r.H.
|
|
Are
the E+E sensors wettable and how do you clean them? |
| E+E
capacitive humidity sensor elements are fully wettable and
cleaning is very easy. The construction of the elements is
robust and mechanically stable.
Cleaning can be done using
distilled water or pure Isopropyl alcohol, industrial
grade. (for example in an ultrasonic cleaner)
|
|
How
fast is the response time of humidity probes? |
| typical
response time t50 for different
sensor types: |
|
capacitive |
resistive |
LiCl |
Dew
point mirror |
electrolytic |
fiber |
|
<
15 s |
<
60 s |
<
5 min |
<
60 s |
<
30 min |
<
10 min |
|
| typical
response time for E+E transmitters: |
| FILTER
TYPE |
t
10/90 [s] |
FILTER
TYPE
|
t
10/90[s] |
| without
filter |
5,5 |
membrane
filter cap |
20 |
| sintered
stainless steel filter |
30 |
sintered
PTFE filter |
13.5 |
|
metal
grid |
7 |
|
|
How
is the long term stability of the E+E sensors in normal environmental
conditions?
LONG
TERM TEST 'OUTSIDE CLIMATE'
EXPERIMENT
10 humidity / temperature
transmitters are tested since 1993 at a meteorological
station near the city of Linz in Austria between two
motorways. Extremely hazardous environmental conditions.
(High air pollution, more than 70,000 cars a day)
RESULTS
The transmitters operate without any failure since 1993.
There is no deviation between transmitters. The long
term drift related to the reference humidity is
approximately 4 % RH over a period of 4 years.
Recalibration is not necessary The test will be
continued.
LONG TERM TEST 'EXTREME INDOOR CLIMATE'
EXPERIMENT
4 humidity / temperature
transmitters were installed on the loft of a residential
building. At this site there are very unstable climate
conditions, fluctuating values in the range of -10 - +50
°C and between 20 and 90 % RH.
RESULTS
After 3 years there is a maximum humidity deviation of
-3% RH. There is no need for recalibration. The test
will be continued.
LONG TERM TEST 'SWIMMING HALL'
EXPERIMENT
Operation of 10 humidity /
temperature transmitters in the climate control system
of a swimming hall with chlorine. The temperature ranges
between 20-40 °C and the relative humidity between 30
and 50 % RH
RESULTS
All transmitters are staying at the same value. The
humidity drift is less than 2%. (see standard deviation
in the charts). There is no deviation in humidity or in
temperature. The test will be continued
LONG
TERM TEST 'COW STABLE'
EXPERIMENT
After
one year of operation in a cattle stable and henhouse
with a very high ammoniac concentration the
transmitter was checked and compared with the initial
characteristics.
RESULTS
Looking at the characteristics curve in the humidity
range between 40 and 80 %rH, there is hardly no
deviation noticeable. In the high and low humidity range
the deviation is a little higher, but can be compensated
by special humidity calibration.
|
|
Long
term test OUTSIDE CLIMATE
Long term test INDOOR CLIMATE
Long term test SWIMMING HALL
Long term test COW STABLE
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