Good morning,
I have casually visited your site, I wonder if you kindly, can point out me a site from which I can to draw electronics circuits for the treatment of the analogical signals with transducer of temperature thermocopule type J (Iron - Costantan) for a range of interest 0-250 °Cs . It will be an interface for a digital converter 0-5Vdc.
The motive for which I need a survey of such temperature (255° degs C) it is due to the impossibility to find in the various hobby electronics sites some information about it. Are there simple circuits of measure of the temperature with a range from 0 to +150 degs C, and more?

1)
I am going to use a microcontroller as MC 68HC11F1(Motorola) or a PIC for the elaboration of the temperature in digital form.
The input voltage of the micro (0 to 5 vdcs) will be converted by an ADC (8 Bits Analog-to-Digital) existing on chip MC 68HC11F1 .

2)
The precision will be compatible with used devices and it must be the smallest possible. It is ideal to have +-2 degs C at the maximum, but I already know that the probe has a tolerance of +-1,5 degs C and that AD596 (Analog Devices) has a maximum error of 4 degs C around 175 degs C. The AD596 is an monolithic temperature setpoint controller that has been optimized for use it at elevated temperatures . It can be configured to provide a voltage output (10 mV/°C) directly from a type J thermocopule signal. You must only use thermocopule J and not thermoresistor!
I would have thought about to correct all by software. Is it possible ?

3)
I hypothesize a distance of 10 meters (32.808 feet) between the transducer (J thermocopule ) and the circuit in examination, on the worst possible hypothesis (environment with electromagnetic noise). The output voltage of the AD596 will have a voltage of 54mV to 2,55V for a range of temperature from 0 to 255 degs C.
I am going to limit the noise between sensor and circuit using an shielded cable .The output signal of AD596 will be the input signal for AD620, a differential amplifier with programmable gain. In out of the AD620 I will have a signal that will be the entry of an IL300F Siemens optocupler an linear amplifier useful in hostile environments.The output signal of IL300F will be the entry of the converter ADC on MC 68HC11F1.To isolate an analog low level signals from a noisy digital environment, many data-acqusisition components have separate analog and digital ground pins. For this, it would be convenient to use IL300F.

4) To facilitate calculations, I am going to use as maximum value of temperature of 255 degs C, but if I have 240 degs C it is OK too.
200 degs C will be the temperature for calibrate the circuit .


These are Information . I hope you can understand .
What do you think about this my possible solution?
Would you like to point out me some technical books or magazine that treat this kind of problem ?

Do you have some other solution ? Do you think that everything is wrong?

I thank you in advance for the time devoted to me and yours suggestions.

Thanks .