Post Go back to editing

AD820 circuit

Hello,

could somebody tell me the purposes of each element in the schematic below?

This is a circuit to measure NTC resistance, but how does it work and why such a configuration, what is the role of the specific components?

Anybody saw such a circuit?

Regrds,

Adam

Parents
  • Hi Adam,

    Thank you for sending this inquiry.

    R4 is the NTC resistor, which is essentially a thermistor with a negative coefficient, i.e. resistance decreases as temperature increases. When R4 is set to 50k (the maximum value of the NTC resistor), 2.5V is at the non-inverting input, which is gained up by 2, which is divided down by the resistor divider. Therefore, 5V at the output and 2.5V across the NTC. This sets the maximum value out of the circuit – which goes into your ADC.

    As temperature increases, the resistance decreases, and the voltage across the NTC will set the voltage at the non-inverting input. The transfer function will be defined by (R4/R3)*5V.

    I hope this helps.

    Best regards,
    Franz

Reply
  • Hi Adam,

    Thank you for sending this inquiry.

    R4 is the NTC resistor, which is essentially a thermistor with a negative coefficient, i.e. resistance decreases as temperature increases. When R4 is set to 50k (the maximum value of the NTC resistor), 2.5V is at the non-inverting input, which is gained up by 2, which is divided down by the resistor divider. Therefore, 5V at the output and 2.5V across the NTC. This sets the maximum value out of the circuit – which goes into your ADC.

    As temperature increases, the resistance decreases, and the voltage across the NTC will set the voltage at the non-inverting input. The transfer function will be defined by (R4/R3)*5V.

    I hope this helps.

    Best regards,
    Franz

Children
No Data