MCP3426 datasheet(34/56 Pages) MICROCHIP

34 / 56 page

MCP3426/7/8

DS22226A-page 34

Figure 6-7 shows an example of measuring both

pressure and temperature. The pressure is measured

by using NPP 301 (manufactured by GE NovaSensor),

and temperature is measured by a thermistor. The

pressure sensor output is 20 mV/V. This gives 100 mV

of full scale output for VDD of 5V (sensor excitation

voltage). Equation 6-3 shows an example of calculating

the number of output code for the full scale output of the

NPP301.

EQUATION 6-3:

EXPECTED NUMBER OF

OUTPUT CODE FOR

NPP301 PRESSURE

SENSOR

The thermistor temperature sensor can measure the

temperature range from -100°C to +300°C. The

resistance of the thermistor sensor decreases as

temperature

increases

(negative

temperature

coefficient). As shown in Figure 6-7, the thermistor (R2)

forms a voltage divider with R1.

The thermistor sensor is simple to use and widely used

for the temperature measurement applications. It has

both linear and non-linear responses over temperature

range. R1 is used to adjust the linear region of interest

for measurement.

Expected

log

100 mV

62.5

μV

PGA

------------------

---------------------

⎝⎠

⎜⎟

⎛⎞

= 10.6 bits for PGA = 1

= 11.6 bits for PGA = 2

= 12.6 bits for PGA = 4

= 13.6 bits for PGA = 8

Number of Output Code =

Where:

1 LSB

62.5 µV with 16 Bit configuration.

1600

PGA

•

()

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⎝⎠

⎛⎞

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