Datasheet

2. Basic Measuring Circuit
FIG. 4.
Vc : Circuit Voltage
Vn : Heater Voltage
RL : Load Resistance
BASIC MEASURING CIRCUIT WITH TGS SENSOR.
Fig.4 Shows the basic test circuit
for use with Sensor type 8813.
The Variation in
resistance of the TGS sensoris measuredindirectly as a Change in voltage appear-
ing across the load resistor RL. In fresh air the current passing through the
Sensor and RL in series is steady,
but when a combustible gas such as propane,
methaoe etc. Comes in contact with the Sensor surface, the Sensor resistance
decreases in accordance with the gas concentration present.
The voltage Change
across RL is the same when VC and VH are supplied from AC or DC sources.
The
circuit must conform to the values listed in Table II.
We feel that this circuit is most suitable for evaluating th.e TGS #813 per-
formante because of the ease in measuring the output signal.
However, when
measuring the output Signal (VRL) of this circuit we suggest that you convert
this value into RS (Sensor resistance) by means of the following formula:
vc x RL
RS =
- RL
VRL,
Zn this way,
the other data in this brothure will be readily available for your
use and your test results will be standardized
in-line with other engioeering
data available from FIGARO concerning TGS #813 Performance.
(4)