AS-MLV-P2 datasheet(8/24 Pages) AMSCO

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[v1-01] 2015-Oct-12

AS-MLV-P2 − Application Information

The resolution of the measurement of RS is recommended to

be better or equal to 1% of the actual reading. This allows

making use of the full performance of the sensor. The

requirements for the A/D conversion of the output voltage Vout

is described in the following section.

The input impedance of the A/D converter should be high

enough not to influence the level of the voltage divider, a ration

of at least 10 between input impedance and values of RS and/or

RL is recommended.

Averaging A/D conversion procedures are recommended in

order to suppress fast resistance changes from the sensitive

layer (resistive noise and change of the resistance due to

chemical influences).

In order to achieve 1% of precision of the read-out of RS, the

A/D conversion of Vout needs lower resolution, if sensor- and

load resistor match. A larger difference between RS and RL

requires a higher resolution of the A/D conversion. The

following figure gives a few examples for VS = 5V.

Figure 9:

Examples for Readout of RS with 1% Resolution (VS=5V)

Examples for Readout of RS with 1% Resolution: The series resistor RL has also the functionality to limit the

power dissipated to the sensitive layer.

If the A/D conversion is single ended (common ground) it might

be useful to change the sequence of load resistor and sensor

resistor in the voltage divider. This enables to increase the

resolution by using a lower reference voltage for the A/D

conversion.

RS [Ohm]

RL [Ohm]

Vout [V]

A/D Voltage Step for 1% Resolution

100

10k

4.95

0.5mV

10k

4.5454

4.1mV

10k

2.5

12.4mV

100k

10k

0.4545

4.1mV

10k

0.0495

0.5mV

100k

4.95

0.5mV

10k

100k

4.5454

4.1mV

100k

2.5

12.4mV

100k

0.4545

4.1mV

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