Datasheet

Revised 10/12
11
TECHNICAL INFORMATION FOR TGS2620
4. Cautions
4-1 Situations which must be avoided
1) Exposure to silicone vapors
If silicone vapors adsorb onto the sensor’s surface, the
sensing material will be coated, irreversibly inhibiting
sensitivity. Avoid exposure where silicone adhesives,
hair grooming materials, or silicone rubber/putty
may be present.
2) Highly corrosive environment
High density exposure to corrosive materials such
as H2S, SOx, Cl2, HCl, etc. for extended periods may
cause corrosion or breakage of the lead wires or
heater material.
3) Contamination by alkaline metals
Sensor drift may occur when the sensor is contaminated
by alkaline metals, especially salt water spray.
4) Contact with water
Sensor drift may occur due to soaking or splashing
the sensor with water.
5) Freezing
If water freezes on the sensing surface, the sensing
material would crack, altering characteristics.
6) Application of excessive voltage
If higher than specied voltage is applied to the
sensor or the heater, lead wires and/or the heater may
be damaged or sensor characteristics may drift, even
if no physical damage or breakage occurs.
7) Operation in zero/low oxygen environment
TGS sensors require the presence of around 21%
(ambient) oxygen in their operating environment in
order to function properly and to exhibit characteristics
described in Figaro’s product literature. TGS sensors
cannot properly operate in a zero or low oxygen
content atmosphere.
8) Polarization
These sensors have polarity. Incorrect Vc connection
may cause signicant deterioration of long term stability.
Please connect Vc according to specications.
4-2 Situations to be avoided whenever possible
1) Water condensation
Light condensation under conditions of indoor usage
should not pose a problem for sensor performance.
However, if water condenses on the sensor’s
surface and remains for an extended period, sensor
characteristics may drift.
2) Usage in high density of gas
Sensor performance may be affected if exposed
to a high density of gas for a long period of time,
regardless of the powering condition.
3) Storage for extended periods
When stored without powering for a long period,
the sensor may show a reversible drift in resistance
according to the environment in which it was
stored. The sensor should be stored in a sealed bag
containing clean air; do not use silica gel. Note that
as unpowered storage becomes longer, a longer preheating
period is required to stabilize the sensor before usage.
4) Long term exposure in adverse environment
Regardless of powering condition, if the sensor
is exposed in extreme conditions such as very
high humidity, extreme temperatures, or high
contamination levels for a long period of time, sensor
performance will be adversely affected.
5) Vibration
Excessive vibration may cause the sensor or lead
wires to resonate and break. Usage of compressed
air drivers/ultrasonic welders on assembly lines
may generate such vibration, so please check this
matter.
6) Shock
Breakage of lead wires may occur if the sensor is
subjected to a strong shock.
7) Soldering
Ideally, sensors should be soldered manually.
However, wave soldering can be done under the
following conditions:
a) Suggested ux: rosin ux with minimal chlorine
b) Speed: 1-2 meters/min.
c) Preheating temperature: 100±20˚C
d) Solder temperature: 250±10˚C
e) Up to two passes through wave soldering machine allowed
Results of wave soldering cannot be guaranteed if
conducted outside the above guidelines since some
ux vapors may cause drift in sensor performance
similar to the effects of silicone vapors.