Ask a question about the LM35CZ temperature sensor

StruggleMySen

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It's like this. I bought an LM35CZ temperature sensor online a few days ago, and then used simulation to make a circuit with no problems. When I used the dual power supply mode given in the sensor manual, it short-circuited as soon as I connected it to my voltage regulator. What's going on? It seems that the Vs and GND inside the sensor are connected together. What's going on? I've been working on it for several days and haven't figured it out yet. I'm about to collapse. I'd like to ask for answers from all the experts.

StruggleMySen

This is the dual power supply circuit diagram given in the manual, because a single power supply cannot measure negative temperature. . . But when I connected the circuit according to this circuit diagram, it short-circuited when I connected my power supply, and the positive power supply and ground were short-circuited. What is going on?

StruggleMySen

This is a simulation circuit diagram I built myself. It goes through an adder and then outputs. The simulation output is fine. I have ruled out the problem with my circuit. I built the simplest dual-power supply circuit myself, but it still short-circuited. . . . Is it a problem with my sensor? . . . Please help me, experts. . . . .

maychang

StruggleMySen posted on 2019-7-14 18:35 This is the dual power supply circuit diagram given in the manual, because a single power supply cannot measure negative temperature. . . But I connected the circuit according to this circuit diagram, and connected...

It is possible that the chip (sensor) is damaged.

Remove it and measure the resistance using a multimeter.

StruggleMySen

maychang posted on 2019-7-14 18:56 It is possible that the chip (sensor) has been damaged. Remove it and measure the resistance of the multimeter.

The two sensors I used were like this... They both short-circuited as soon as they were connected...

maychang

StruggleMySen posted on 2019-7-14 19:01 Both sensors I use are like this... They short-circuit as soon as they are connected...

Did you buy both sensors from the same company? If they were from the same company, then there is a high possibility that both sensors are faulty.

StruggleMySen

maychang posted on 2019-7-14 19:32 Did you buy the two sensors from the same company? If they were from the same company, then there is a high possibility that both sensors are broken.

Yes, I bought it from a company, my god... This is so unlucky... Master, is it possible that the problem is with this circuit, that is, the problem with the circuit in the data sheet... I think this possibility is relatively small...

maychang

StruggleMySen posted on 2019-7-14 19:52 Yes, I bought it from a company. Oh my god... This is too unlucky... Master, is it possible that the problem is with this circuit, that is, the data sheet...

The chances of the circuit in the manual being wrong are extremely small.

This is a fairly old chip that has been used by countless people.

It is possible that you made a welding error.

maychang

StruggleMySen posted on 2019-7-14 19:52 Yes, I bought it from a company. Oh my god... This is too unlucky... Master, is it possible that the problem is with this circuit, that is, the data sheet...

I guess your LM35 is in TO-92 package. The chip datasheet has already indicated that it is in Bottom View.

dcexpert

Analog chips like LM35 are generally not easy to damage, but the possibility of buying fakes is relatively high.

lct2000

Is it short-circuited when powered on? Is it short-circuited when not powered on?

StruggleMySen

maychang posted on 2019-7-14 19:58 I guess your LM35 is a TO-92 package. The chip datasheet has already indicated that it is a Bottom View.

The correct package is TO-92. I know the bottom view and I haven’t connected the wires wrong. . .

StruggleMySen

dcexpert posted on 2019-7-14 21:09 Analog chips like LM35 are generally not easy to damage, but the possibility of buying fakes is relatively high.

Uh... maybe I really bought a fake one. I bought another one to see if this more expensive one works...

StruggleMySen

lct2000 posted on 2019-7-14 21:12 Short circuit when powered on? Short circuit when not powered on?

After powering on, my voltage source Vs and GND are short-circuited. I suspect that these two pins are short-circuited inside the sensor.

StruggleMySen

lct2000 posted on 2019-7-14 21:12 Short circuit when powered on? Short circuit when not powered on?

There is no short circuit when there is no power. . . What is going on?

StruggleMySen

dcexpert posted on 2019-7-14 21:09 Analog chips like LM35 are generally not easy to damage, but the possibility of buying fakes is relatively high.

Great God, are you there?

dcexpert

StruggleMySen posted on 2019-7-15 15:52 Is the master here?

It is not necessarily a short circuit. It may be that the power supply and ground are connected reversely, and the internal protection diode is turned on.

StruggleMySen

dcexpert posted on 2019-7-15 15:55 It is not necessarily a short circuit. It may be that the power supply and ground are connected in reverse, and the internal protection diode is turned on.

It doesn't seem to be connected reversely... But it short-circuit when connected...

dcexpert

StruggleMySen posted on 2019-7-16 10:01 It doesn’t seem to be connected reversely. . But it short-circuit when connected. . . .

I feel like I might have bought a parallel-imported domestic chip, and its functions may not be exactly the same as the original.

You can also try a single-power supply circuit. The data sheet suggests using two diodes, so there should be no short-circuit problem.

dcexpert

StruggleMySen posted on 2019-7-16 10:01 It doesn’t seem to be connected reversely. . But it short-circuit when connected. . . .

If you just want to test negative temperatures, there are still many options, such as NTC, DS18B20, etc. Many temperature sensors have a bias voltage at 0 degrees, so a single power supply can also measure negative temperatures. LM35 may have no advantages over other sensors except for its extremely large operating voltage range.