UNISENSE N2O-50, Руководство пользователя

Страница: 9 / 23

9
GETTING STARTED
U
NPACKING AND CONNECTING A NEW SENSOR
When receiving a new microsensor, first remove the
shock-absorbing grey plastic net. Then secure the sensor
in a safe position (e.g. micromanipulator or calibration
chamber) before connecting it to the measuring meter.
The signal from the nitrous oxide sensor is generated in
picoamperes. Therefore the nitrous oxide sensor must
be connected to a picoammeter amplifier unit during
measurements.
P
RE
-
ACTIVATION AND
P
OLARIZATION
Please see procedure below.
Pre-activation period : Nitrous oxide sensors have a metal
cathode which during normal exposure to oxygen over
time will acquire an oxidized surface layer. If the sensor
is new or has not been used recently, this layer must be
“pre-activated” in order for the sensor to work. This is
done by applying a voltage of -1.3 V for 30 minutes
prior
to the period of polarization which is required for most
electrochemical sensors.
Stabilization period : The electrolyte inside the sensor can contain
large amounts of oxygen which must always be removed before the
sensor is stable. This is done by the guard cathode inside the sensor
whenever the sensor is polarized, i.e., connected to an amplifier.
This process requires some time, depending on the dimensions and
exact proportions of the individual sensor.
IMPORTANT:
If the sensor is new or has been disconnedcted for > 4 hours, follow
the PRE-ACTIVATION PROCEDURE below. For recently used N
2
O
sensors, follow the POLARIZATION PROCEDURE below.
Please read both sections before starting the relevant procedure.
WARNING
Do not remove
the seal and
protective
plastic tube
before these
steps and
calibration are
successfully
completed.
WARNING
Incorrect
polarization
may destroy the
sensor.