MCP3422 datasheet(34/58 Pages) MICROCHIP

34 / 58 page

MCP3422/3/4

DS22088C-page 34

Figure 6-6,

shows

example

using

the

MCP3424 for four-channel thermocouple temperature

measurement applications.

FIGURE 6-6:

Four-Channel Thermocouple Applications.

With

Type

thermocouple,

can

measure

temperature from 0°C to 1250°C degrees. The full

scale output range of the Type K thermocouple is

about 50 mV. This provides 40 µV/°C (= 50 mV/

1250°C) of measurement resolution. Equation 6-1

shows the measurement budget for sensor signal using

the

MCP3422/3/4

device

with

18 bits

and

PGA = 8 settings.

With

this

configuration,

the

MCP3424 can detect the input signal level as low as

approximately 2 µV. The internal PGA boosts the input

signal level eight times. The 40 µV/°C input from the

thermocouple is amplified internally to 320 µV/°C

before the conversion takes place. This results in

20.48 LSB/°C output codes. This means there are

about 20 LSB output codes (or about 4.32 bits) per 1°C

of change in temperature.

EQUATION 6-1:

VDD

CH2-

VSS

CH3+

CH2+

CH3-

CH1-

CH4+

CH1+

CH4-

SDA

SCL

VDD

0.1 µF

10 µF

TO MCU

(MASTER)

MCP9800

Isothermal Block

Thermocouple Sensor

Heat

SCL

SDA

SCL

SDA

SCL

VDD

SDA

SCL

SDA

SCL

Adr1

Adr0

MCP3424

Input Signal Level after gain of 8:

Where:

1 LSB

15.625 µV with 18 bit configuration

Detectable Input Signal Level

15.625

μV/PGA

1.953125

μV for PGA 8

μV/°C

() 8

320

μV/°C

•

No. of LSB/°C

320

μV/°C

15.625

μV

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

20.48 Codes/°C

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