Analog input - voltage ranges

Hello everyone !
I need the voltage ranges that are used as inputs to Analog input modules for thermocouple support ( Type B,E,J for example) . Are those standard ranges? Also what voltage ranges should the analog input module support for RTDs (e.g PT100) ?
I am asking because some of the AI modules declare explicitly the thermocouple , RTD support and some of them do not . I wouldn't like to go to specific examples , but to a more general rule if any.

Thank you in advance

BobB - answered your question

RTD is not a voltage input but is a resistance measurement across a resistor and also the return wire so the resistance of the wire can be deducted. Thermocouples are millivolts and dependent on the type of thermocouple - they are also not generally linear and calculations are done in the card. Here is a link to thermocouple charts http://www.thermibel.be/documents/th...es.xml?lang=en and an RTD chart http://www.omega.com/temperature/z/pdf/z252-254.pdf - Mr Google is wonderful.
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Regards,
Garry
http://www.accautomation.ca

Many devices that handle thermocouples (T/C) state that they can also handle millivolts, because a thermocouple is always in the mV range. The spec sheet will tell you whether such is the case.

Likewise, many devices that handle RTDs state that they also handle resistance (like a slidewire or potentiometer) and specify the resistance range that they handle. The spec sheet will tell you whether such is the case.

FYI, RTD circuits typically drive 1mA (or less) of excitation current through the RTD. It takes some digging to discover the excitation current value; most often it is not published. But 1mA through 120 ohms is still in the mV range. Although the internal measurement is a voltage measurement, the excitation current required for a resistance measurement limits its use to resistance measurement, not a a raw voltage measurement.

If a device with a T/C input does not state that it can be configured to handle mV, then you're likely to have an error using it for mV because
- T/Cs are not linear so the temperature is calculated with a polynomial from the mV signal. Most mV outputs are linear. Putting linear data into a polynomial distorts it.
- the cold junction temperature is added to the T/C measured temperature, creating a huge error (offset).

Thank you both !
I accidentally posted the same thread twice , and started replying to the other one(http://www.plctalk.net/qanda/showthread.php?t=93848 ) . Please feel free to join the conversation there, as I don't want this to be considered as spamming!
Thank you