Have you ever seen such a collection circuit? ADC signal collection

小太阳yy

Have you ever seen such a collection circuit? ADC signal collection [Copy link]

 

Why does it feel so strange? I have never seen such a design. Does anyone know about it? Can you explain the functions of each component?

maychang

I've never seen a circuit like this.

If a diode is connected in series with the 5V power supply voltage, won't the voltage across R3 or the voltage across NTC, R1, and R2 be stabilized to the power supply voltage minus a PN junction voltage drop? No matter how the NTC changes, the voltage across R3 remains basically unchanged.

maychang

If the voltage across R3 remains essentially unchanged regardless of how the NTC changes, what is the point of such a circuit?

仙猫

Could it be that the surveying was wrong?

The position of the diode should be a resistor, and the position of R3 is more like a protective voltage regulator (or TVS diode).

dcexpert

I think the above comments are correct, or the power supply is drawn wrong.

hqli126

Slow motion signal detection

Gen_X

This is a simple temperature measurement circuit, and the measuring element is NTC.

The 5V power supply and the GND of R3 may be drawn reversely.

Otherwise the MCU will be useless!

chunyang

The circuit must be wrong. Take a good look at the original circuit again.

小太阳yy

chunyang posted on 2021-8-22 20:51 The circuit must be wrong, please check the original circuit again.

Okay sir, I don't feel right either.

小太阳yy

Gen_X posted on 2021-8-22 10:48 This is a simple temperature measurement circuit, the measuring element is NTC. It should be that the 5V power supply and the GND of R3 are drawn inversely. Otherwise, the MCU will not work! ...

It is similar to the NTC measurement circuit, but it still feels like there is a problem

小太阳yy

maychang posted on 2021-8-13 16:14 I have never seen such a circuit. A diode is connected in series to the 5V power supply voltage. The voltage across R3 or the voltage across NTC, R1, and R2 is not stabilized to the power supply...

There is indeed a problem. I am also confused. The measurement results are very confusing.

qwqwqw2088

The circuit is not right.

What does it mean? I am confused

sfcsdc

The resistor is not marked on the picture

1. Using NTC, when the temperature rises, the resistance will decrease, the current flowing through the diode will increase, and according to the volt-ampere characteristics of the diode, the forward conduction voltage drop of the diode will increase;

2. When the temperature rises, according to the temperature characteristics of the diode, the forward voltage drop will decrease under the same current.

If you choose the right resistor, the voltage sampled by the MCU will change with temperature.
If the circuit is correct, it is possible to use the temperature characteristics of the diode to compensate for the temperature drift of some components, making the value sampled by the NTC more accurate.