electronics - Thermocouple signal amplification using INA126P -


i'm trying interface thermocouple microcontroller. thermocouple produces low voltage, use ina126p instrumentation amplifier amplify voltage. i'm using +5v v+ , gnd v- , vref=2.5v.

but in datasheet says input common mode voltage 1.5v 3.5v (from graph). tried add offset thermocouple input. i've done in 2 ways:

  • using op-amp ,
  • using voltage divider.

here schematics (sorry, hand-drawn):

using voltage divider

using opamp

may know if circuits correct?

either circuit should work. divider 1 better error standpoint because offset voltage (from divider) common mode input amplifier, cancelled. errors 2 op-amps , associated resistors random, , not cancelled. first circuit more accurate. don't need 10k resistor on input, 1k's same function. , 1k's 10k, if want save current.

you can better parts ina part. have used ad620 chip in past results. believe has better offset specs, important spec in thermocouple amplifier.

also, pay close attention voltage levels regard rails. running single supply possible, check whole thing doesn't flake out when input and/or output signals approach limits of operation outlined in data sheet. beware output voltage not go rail rail also.


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