AS-MLV-P2 datasheet(7/24 Pages) AMSCO

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[v1-01] 2015-Oct-12

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AS-MLV-P2 − Application Information

Due to the characteristics of the sensor, there are some issues

to be taken care of while implementing. The operation

temperature of the sensor has to be kept constant; therefore

the circuit on heater site shall have the possibility to be

regulated. The critical issue of the sensor resistance is the wide

range of values which has to be covered during operation.

All following circuits are meant to be examples which have to

be adapted carefully to the different applications.

Sensor Resistance

The sensitive layer can change its resistance over several orders

of magnitude, depending on the production and gas

exposition. The electrical power dissipated in the sensitive layer

must be limited and must not exceed 2mA. This power shall also

avoid performing high changes over short time. Because of this

issue a measuring range shifting realized with series resistors

will have an effect to the sensor signal and should be avoided.

As a suggestion we measure the sensor resistance with a simple

voltage divider as shown in Figure 8. VH determines the heater

voltage and therefore the operation temperature of the sensor.

This regulation is described in a later chapter. Here we focus on

the sensor resistance measuring. To meet the described

specification a value of 10kOhm or 100kOhm for the load

resistor (RL) and a Voltage of 5V for VS is a good starting point

for a broad range of the sensor applications. A high precision

noise free voltage source is recommended for generating VS. RS

and RL form a voltage divider, which can be used to calculate

RS (see EQ 1).

Figure 8:

A Basic Measurement Circuit for the Sensor Resistance

Application Information

(EQ1)

out

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–

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

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Vout

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