Conversion of the temperature value from lm35

[ings]

hello plz i m connect lm35 to sensor 2 pin of rn 171 (16bits) and i m receiving this data from the lm35:
3D1Z (HExa)
so the value is 15642 (decim)
so to do the conversion i m doing this step but i can't find a true value of temperature :
the value of voltage output of sensor is :
U=114*15642/(2^16-1)
the value of temperature is :
T=aU+b--> from datasheet of lm35 a=0.9 and b= -40
so i find that the value of temperature is 62°C which is false
so can you help me please
thanks in advance

 

[D.A.(Tony)Stewart]

Are we assuming 10mV?'C and what is the LSB value?

 

[Warpspeed]

Recorded value 15,642
Full scale value 65,535

Assuming 65,535 full scale equals 5.00 volts (?)
Output from LM35 will be 15,642/65,535 x 5.00v = 1.193 volts

Output of LM35 is 10mV per degree Celsius
1.193v = 119.3 degrees Celsius

 

[hobbyckts]

hello plz i m connect lm35 to sensor 2 pin of rn 171 (16bits) and i m receiving this data from the lm35:
3D1Z (HExa)
so the value is 15642 (decim)
so to do the conversion i m doing this step but i can't find a true value of temperature :
the value of voltage output of sensor is :
U=114*15642/(2^16-1)
the value of temperature is :
T=aU+b--> from datasheet of lm35 a=0.9 and b= -40
so i find that the value of temperature is 62°C which is false
so can you help me please
thanks in advance

How come the Hexa decimal Value for you it shows 3D1Z. It is worng

I guess it should be 3D15. Then you will get the decimal value of 15637

15637*5 /65535 = 1V

So if Vout is 1V , then, Temperature = 100 degree C


Provide correct Hexa decimal value..

 

[ings]

the power supply to the sensor is 3.5V
and the data in hexa come from my rn171 EK

- - - Updated - - -

the value hex is obtained with this command:
set q sensor 0x08 (pin2)

 

[hobbyckts]

What is the value which you are getting? Provide it correctly...

Do you know the temperature at which your IC has been placed? May be you might have read through someother sensor for cross verification.


You only need the method to calculate the temperature value right?

 

[ings]

the temperature of the room is between 25°C and 30°C
but i think that the hex value is false because with this line
set q sensor 0x08
i have the value
1D110000000000003D0C0000000000000000
THE pin of sensor is pin 2
and with rn 171 ek i have this pin
9 8 7 6 5 4 3 2 1
9GND
8 SENSIR 3(1.2v)
7 SENSOR 6
6 SENSOR 4
5 SENSOR 5
4 SENSOR 7(1.2v)
3 SENSOR 5(3.3v)
2 SENSOR 4(3.3v)
1 SENSOR power

- - - Updated - - -

when i write
set q sensor 0xff
i find this value:
*HELLO*1D11CF29CF2907EF3D10156907FC308930A6 HTTP/1.0
Host: dns1
i can't understand the value of my received frame

 

[betwixt]

Now I'm really confused. That looks like part of a web page header, not a temperature measurment. I'm not famililar with the evaluation kit but the LM35 provides an analog voltage output so something on does a conversion to a different format already. It isn't producing a web page with the temperature displayed on it by chance?

Brian.

 

[hobbyckts]

**broken link removed**

Go thru this document carefully. You will get what is needed

 

[ings]

in this doc i have
2 Bytes
GPIO
Channel 0 Channel 1 Channel 2 Channel 3 Channel 4 Channel 5 Channel 6 Channel 7
0F30 0000 1111 2222 3333 4444 5555 6666 7777

so pin 2 is the channel 2??

 

[hobbyckts]

Seriously the explanations you are providing is not quite clear to me understand. Provide clear explanations people are there to help you out

 

[ings]

First, i'm sorry for my bad english.
for my problem is in conversion of the hex value obtanined from my RN171-EK
i m doing this step :
1. i connect the RN171 EK to the lm35 via sensir 3
2. i hope to post sensor data automatically from lm35 in my pc

set q sensor 0xff
set sys auto 30  
set option format 7

so i obtained this frame
*HELLO*05170807080307F03DE407ED0801309330A5 HTTP/1.0
Host: dns1
so from the datasheet of rn171-ek page 77
**broken link removed**

The analog-to-digital converter is 14 bits on a 400 mV signal, which translates to about 24 microvolts (0x61A80 in hex). When you use the show q command in Command mode, the module displays the raw readings. However, for HTTP web posting and UDP broadcast packets, the module shifts the reading by 4 bits (which is a divide by 16) resulting in a 16-bit number. Therefore, if you want the actual voltage sampled, you must take the 16-bit number and shift it left by 4 bits to get the number of microvolts. If you the value in millivolts (and do not need high accuracy), right shift by another 6 bits, which is the same as dividing by about 1K.

so for my sensor lm35 the hexa velue is
3DE4
and the value of temperature is betwen 20 and 30°C
Can you help me please

 

[FvM]

The analog-to-digital converter is 14 bits on a 400 mV signal, which translates to about 24 microvolts (0x61A80 in hex).

The statement sounds confused and doesn't make much sense. It sounds like the author has problems to phrase clear sentences. If he had e.g. stated "the 14-bit ADC has a full-scale range of 400 mV which translates to an LSB resolution of about 24 µV", everybody would understand it. The relation to hex number of 0x61A80 needs explanation too, apparently there's a nominal scaling of 1V = 2^24.

- - - Updated - - -

so for my sensor lm35 the hexa velue is
3DE4
and the value of temperature is betwen 20 and 30°C

3DE4/2^16*100°C = 24.2°C

 

[ings]

thanks for your response but please can you explain me why you have multiple *100°C and why you have choose 16bits and not 14bits

 

[FvM]

There's a physical ADC range (400 mV) with 14 bit resolution (24 µV LSB) and a virtual output range of 1V with 24 respectively 16 bit resolution, 16 bit is used in the wireless frame. LM35 has 10 mV/K, 0 to 100 degree is giving 0 to 1V output.