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1N4148 as temperature sensor...

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davorin

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diode temperature sensor

Does someone has a simple schematic to use 1N4148 diode as temperature sensor?

According to datasheet it should work up to 200 degrees celcius and above...
Just need to verify some temperature profile for BGA soldering (o;
 

davorin

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diode as temperature sensor

Hmm...not really any 1N4148 applications in there...

Only one sensor application using normal NPN transistor...though probably I can replace Vbe used with 1N4148...


I just recall using a 1N4148 in the feedback path on an operational amplifier....not sure though (o;
 

jorgito

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diode temperature sensor circuit

Hello,
I think the simplest way to do it is just a temperature compensated current source driving the 1N4148, you get a 2.2 mV/K slope. Small signal transistor (usually metalic case) temperature probes allow lower thermal constants but are replaceable by diodes.
Best regards.
 

RegUser_2

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2n2222 transistor temperature sensor

Just apply about 100 uA constant current trough the diode and measure the voltage drop across it. The thermal coefficient depends of the technology and is about -2.2 mV/K for a silicon diode. Your readout needs to remove offset (adjust zero), and be able to adjust the gain of your amplifier(adjust the sensitivity). The calibration is done by deeping the diode probe intoa melting ice for 0C (zero adjust) and some other object with knownt high temperature in the range of interest (sensitivity adjust)
 

ME

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1n4148 temperature coefficient

I made a temperature monitor once, using a 1N4148 as sensor, I connected the diode to an opamp in a special way to make sure a constant current runs through the diode at the same time as the OPAMP measured the voltage across the diode.
If the current through the didode is constant regardless of temperature, the temperature reading will be more linear.
I will try to look for my old schematics.
 

djolestojic

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1n4148 sensor

Maybe you can use LM334 temerature dependent current source.

(1N4148 is used to compensate the LM334's drift caused by the temperature variations)
 

sinatra

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use diode as temperature sensor

HEllo all.
I think you cannot use a single diode to measure a certain temperature.
You need 2 diodes, one will be used as a reference.
Let's supose that you have both diodes fed by identical current sources I0.
One of the diodes, D1, is the measuring device and is in physical contact with the body you want to measure the temperature. The other diode, D2, the reference is inside of a box (electronic termometer that you are building) measuring the ambient temperature.
Vd1=Vt1 * ln (I0/Is1)
Vd2=Vt2 * ln (I0/Is2)
Is1=Is2 if the diodes are identical.
So,
Vd1*q/(K * T1) = Vd2*q/(K*T2) , T2= ambient temperature, T1= temperature to measure.
Then we find easily the temperature T1
T1= (T2/Vd2)*Vd1
You just need to measure Vd1 and you have T1. Since T2/Vd2 is constant and can be measured only once during the calibration.......2 diodes in the same temperaute, etc...
I hope it can help.
greetings to all
S.
PS: The diodes can also be replaced by bipolar transistors with metalic case like 2N2222.
 

ME

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temperature sensor schematic

I have made a temeperature probe using only one diode and it was very accurate in the tested range from 0 deg. celcius to 70 deg. celcius. The biggests deviation in the whole range was 0.3 deg.

All measurements was made at the same ambient temperature approx 20 deg. celcius, so I'm not sure if changes in the ambient temperature will affect the accurancy of the readings or not. I probably should have tested that too.
I will try to post the schematics later.


I have heard that it is better to use a transistor with the collector and the base short-circuited as sensor instead of a diode, even if it is a plastic transistor.
You can read about it in section three of this data sheet:
**broken link removed**

Here's also some useful reading from Maxim:

Temperature Monitoring Using the MAX1253/54 and MAX1153/54
**broken link removed**

Compensating for Ideality Factor and Series Resistance Differences between Thermal Sense Diodes:
**broken link removed**



It's important to keep the diode current low to avoid self-heating, but not too low to get accurate readings.
 

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1n4148 as a temperature sensor

hi

may be this will help you 1n4148 based thermometer a value of res reading as 2002k where as it is 2.2k
 

Fragrance

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1n4148 temp sensor

hi

this is best themostat based on 1N4148 with great accuracy and range from -10 135 degree centigrate
 

Mazi3

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temperature sensor diode

it is too hot to measure temperature with ordinary diode.

use high temperature sensor like pt100....
 

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temperature sensor 2n2222

1N4148 can stand how many degree?
 
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arun_123

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diode temperature sensors schematic

how to sense to the temperature using 1N4148 can you plz sugest ckt of site relate to 1N4148
 

Fragrance

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1n4148 thermometer

arun_123 said:
how to sense to the temperature using 1N4148 can you plz sugest ckt of site relate to 1N4148

hi just two post above i have posted working circuit for this open your eyes man:D
 

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1n4148 temperatur sensor

Since the soldering temperatures are above 200C, I think you should use a thermocouple. Why did you want to use the diode for the job? Is it a requirement?
 

toffi

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diode temperature sensor 1n4148

Thank fom long time I'm search abut this information
 

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