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#### Flying

##### New Member
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Hi, I m new. Hope u all can help me.. Currently, doing for school project. The title is human body temperature monitor by telemetry system.
I connected the circuit as in Figure 2(circuitTested.jpg) . It didn't work as i expected. At room temperature , I obtained voltage output range from around -1.2 to 1.2 V by vary R1. It supposed be 2.0-2.5V output at room temperature.I use TLE2022IP(OP-amp).
Question:
1. Does the circuit in data sheet work? How it work ? Or my own circuit is connect in wrong way?
2. How should i active the AD 592? should i supply -5V to pin(-) of AD590 and pin(+) of AD590 to ground?
3. If i want to change the voltage supply to 5V , then i modify the circuit?
4. May i use voltage divider rule ( by 2 series resistor) to supply 2.5 V from 5V?
5. How to trim the accuracy of temperature sensor as shown in data sheet? Should i test the temperature sensor at 0'C?
6. DO u hav other suggestion circuit for this AD592 circuit?
7. May u give me suggestion on my project title?

This is my first time post. This web side suggested by my fren so i try to log in here.. ^_^ Hope to get answer from u ...

#### audioguru

##### Well-Known Member
Flying said:
I use TLE2022IP(OP-amp).
Did you use a positive and a negative supply?

should i supply -5V to pin(-) of AD590
Yes.

and pin(+) of AD590 to ground?
No. Connect it to the input of the opamp and the two resistors as in the schematic.

If i want to change the voltage supply to 5V , then i modify the circuit?
With only a 5V supply, the output voltage range of the opamp is severely reduced. You can reduce the gain of the opamp to compensate, then the resolution will be much less than 100mV/degree C.

May i use voltage divider rule ( by 2 series resistor) to supply 2.5 V from 5V?
Yes, it should work fine.

Should i test the temperature sensor at 0'C?
Yes. As per the instructions.

#### Flying

##### New Member
Yes. I connected +15 and -15 To Op-AMP.
After i connected the -5V to pin(-) of AD592, then positive of power supply connected to ground?
Did u know the calculation of the op-amp gain (relationship bewteen Vo and Vin) ? Difference Amplifier?
THX

#### audioguru

##### Well-Known Member
Flying said:
I connected +15 and -15 To Op-AMP.
Good.

After i connected the -5V to pin(-) of AD592, then positive of power supply connected to ground?
Of course. Did it work?

Did u know the calculation of the op-amp gain (relationship bewteen Vo and Vin) ? Difference Amplifier?
R2 adjusts the gain so that high temperatures create the correct output voltage. The opamp is used with a difference of two currents as its input which makes a voltage output. Vin is always 0V.

#### Flying

##### New Member
audioguru said:
Good.

Of course. Did it work?

R2 adjusts the gain so that high temperatures create the correct output voltage. The opamp is used with a difference of two currents as its input which makes a voltage output. Vin is always 0V.

Do u mean tht pin(+) and pin(-) input of OP amp are always 0?
If i change the input voltage from 2.5V to 5V , wat is the suggested resistors value? or remain same?

#### audioguru

##### Well-Known Member
Flying said:
Do u mean tht pin(+) and pin(-) input of OP amp are always 0?
Yes, very close to 0V. The + input of the opamp connects directly to 0V through the 8.2k resistor. The opamp has a voltage gain of about 200,000 so the negative feedback through the 100k resistor and R2 makes the - input almost the same voltage as the + input. The voltage at the - input changes only when the output of the opamp saturates.

If i change the input voltage from 2.5V to 5V , wat is the suggested resistors value? or remain same?
I think then the 9k resistor should be 18k and R1 should be 2k so the current remains the same. The 2.5V was selected from a very accurate voltage reference. Your 5V probably won't be accurate and stable enough.

#### Flying

##### New Member
audioguru said:
Yes, very close to 0V. The + input of the opamp connects directly to 0V through the 8.2k resistor. The opamp has a voltage gain of about 200,000 so the negative feedback through the 100k resistor and R2 makes the - input almost the same voltage as the + input. The voltage at the - input changes only when the output of the opamp saturates.

I think then the 9k resistor should be 18k and R1 should be 2k so the current remains the same. The 2.5V was selected from a very accurate voltage reference. Your 5V probably won't be accurate and stable enough.

1. I didn't use AD1403 in my circuit. is it not so much effect, rite?
2. It is hard for me to trim the AD592 at 0'C. I haven't idea how to trim it bec lack of equipment. Or may i trim it at room temperature ? Should i close the AD592 to ICe at lower temperature? Will the AD592 short circuit or spoil if touching with water or ice?

#### audioguru

##### Well-Known Member
Flying said:
1. I didn't use AD1403 in my circuit. is it not so much effect, rite?
If you use a voltage divider with stable resistors and from a stable 5V supply it will work the same.

2. It is hard for me to trim the AD592 at 0'C. I haven't idea how to trim it bec lack of equipment. Or may i trim it at room temperature?
Stir ice in water to make 0 degrees C. Then adjust for 0V.

Will the AD592 short circuit or spoil if touching with water or ice?
I don't know if the plastic package is waterproof (it probably is) but the legs will corrode if wet. Moisture will upset the circuit.

#### Overclocked

##### Member
Flying said:
1. I didn't use AD1403 in my circuit. is it not so much effect, rite?
2. It is hard for me to trim the AD592 at 0'C. I haven't idea how to trim it bec lack of equipment. Or may i trim it at room temperature ? Should i close the AD592 to ICe at lower temperature? Will the AD592 short circuit or spoil if touching with water or ice?

Cover the sensor with Silicone, you know, the housing type stuff. You could also mount it on a peice of Metal (copper) and the put the metal in water so it doesnt touch the sensor. The metal is thermal conductive, so your results should be pretty accurate.

You can also Stick it in a Freezer or Fridge and calibrate the circuit there. You could also go outside, since its a known Temp and Calibrate it until you read what the outside temp is.

Or do it another way, If your sensor produces a certain voltage at a certain temp, Adjust the circuit until you get that voltage (ie, take the input of the circuit, and inject a small signal into it. Adjust the dsiplay until you get the temp reading)

#### Flying

##### New Member
thx u , guys.
i wil try it... ^_^

#### subhro_jana

##### New Member
I am also going to make a similar project. That of a temperature control of a boiler ... can any one plz... let me know that whether AD592 is emerseble in water???

#### Overclocked

##### Member
I am also going to make a similar project. That of a temperature control of a boiler ... can any one plz... let me know that whether AD592 is emerseble in water???

Pick up this months issue of Nuts and Volts (October 2008). Lots of good info for that sorta project.

#### la_viola89

##### New Member
Hi, I am also new here.

I already connected the temperature sensor as below:

+5 to + 15 volts ----------------------; +
;--------------' -
|
stamp P5 ---/\/\----|
100 |
--- 0.1uF
---
|
common ------------'

(source:OWL2 to LM34 & AD590 temperature sensors)

and this is the source code for basic stamp to read the temperature:
cal con 64020 ' calibration constant to be determined
X var word ' raw count from RCtime, 2uS resolution
kelvin var word ' kelvin temperature
degC var word ' temperature in 'C
degF var word ' degrees Fahrenheit
low 5 ' initial discharge the capacitor on p5
loop:
RCtime 5,0,X ' get charging time
low 5 ' discharge the capacitor
Kal = X*273
kelvin = cal/X
degC = kelvin-273 ' calculate temperature
degF = kelvin *9/5 - 460
debug cls,? X,? Kal,? kelvin,? degC, ? degF
' show raw count, and temperatures (positive display only)
pause 2000 ' 2 second delay for demo
goto loop

using that circuit & that program, my charging time (X) is keep changing in large range. what should i do for this case?

I hope somebody can help me ^_^

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