MCP3426 datasheet(32/56 Pages) MICROCHIP

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MCP3426/7/8

DS22226A-page 32

Figure 6-6, shows an example of using the MCP3428

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 MCP3426/7/8 device with 16 bits and PGA = 8

settings. With this configuration, the MCP3428 can

detect the input signal level as low as approximately

7.8 µV. By setting the internal PGA option to x8, the

40 µV/°C input from the thermocouple is amplified

internally to 320 µV/°C before the conversion takes

place. This results in about 5 LSB output codes per

1°C of change in temperature, with 16-bit conversion

mode.

EQUATION 6-1:

VDD

CH2-

VSS

CH3+

CH2+

CH3-

CH1-

CH4+

CH1+

CH4-

SDA

SCL

VDD

MCP3428

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

Input Signal Level after gain of 8:

Where:

1 LSB

62.5 µV with 16 bit configuration

Detectable Input Signal Level

62.5

μV/PGA

7.8125

μV for PGA

μV/°C

() 8

320

μV/°C

•

No. of LSB/°C

320

μV/°C

62.5

μV

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

5.12 Codes/°C

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