Powerex MTSD0503 - Integrated Dew Point Monitor Maintenance; Sensor Calibration and Adjustment; Replacing the Filter; Daily Auto-Calibration

Dew Point Monitor
Powerex • 150 Producon Drive • Harrison, OH 45030 • USA
P 1.888.769.7979 • F 513.367.3125 • www.powerexinc.com
IN907800AV • 08/2018
Page 28 of 40
Integrated Dew Point Monitor Maintenance
Sensor Calibraon and Adjustment
The sensor is fully calibrated as shipped from the factory (see
calibraon sheet included in the main system manual). With the
Daily Auto-Calibraon feature (listed below) the sensor may not need
replacement for up to 10 years. The manufacturer recommended
replacement interval is 2 years from system start-up or if sensor
should malfuncon.
Replacing the Filter
The sensor is protected with a stainless steel sintered lter. The
ltering grade is 34 um.
The lter is recommended to be changed whenever it looks dirty or
as a part of the periodical maintenance procedure. The recommended
replacement interval depends heavily on the applicaon and can vary
from less than a year to several years. Dirty or corroded lter may
cause increased response mes. In case the sensor is used in a drying
system with silica gel (or other drying agent) the dust from the dryer
may collect on the sensor slowing the response but also generang a
micro climate around the sensor altering the dew point at the sensor.
This is easily corrected by changing or cleaning the lter.
Touching the sensor may damage it. Special
aenon shall be paid to avoid touching the sensor
when removing and replacing lters.
Daily Auto-Calibraon
The Daily Auto-Calibraon feature of the sensor is an automac
procedure which greatly reduces the possible dri in the dry end of
the dew point measurement. It is performed at one hour intervals, and
when the power is switched on. During auto-calibraon the sensor
is warmed for a short period (< 1 min) and the sensor capacitance
values are evaluated at the elevated temperature. The possible dry
end dri is then corrected to correspond to the calibrated values.
During the auto-calibraon the transmier outputs the Td value prior
to the procedure. Auto-calibraon is carried out only if several criteria
for the measurement environment are fullled. This ensures the
reliability of the adjustments, and maintains the excellent long term
stability that the patented technology oers. These criteria include
e.g. a suciently stable enough moisture level in the measured
atmosphere. If the condions are not fullled, the auto-calibraon
funcon is postponed unl the sased condions are reached.
Sensor Purge
Sensor purge is also an automac procedure that minimizes the
dri at the wet end readings of the dew point measurement. Sensor
purge is performed once a day or when the power is switched on.
The sensor is heated for several minutes which will then evaporate all
excess molecules out of the sensor polymer. This, together with the
auto-calibraon results in a very small dri of the sensor due to the
very linear behavior of the polymer technology.
Sensor Warming in High Humidity
Addionally the sensor has a warming feature which prevents the
sensor and lter from becoming wet in high humidity. High humidity
can be present when the dew point temperature rises close to the gas
temperature. Sensor warming is switched on automacally when the
humidity level in the measured gas increases to a level where dew
can start to form. The advantage of sensor warming is rapid response
of dew point measurement. A wet sensor and lter would otherwise
result in a dew point equal to ambient temperature (i.e. RH=100%). If
the sensor becomes soaked in any way, it will fully recover and return
back to normal operaon aer it dries out.