How many thermocouples can I connect to the ADuC7060/61 ?
In CN0214, an RTD is used for cold-junction compensation - this is measured via the ADC.
The reference source used by the ADuC7060 ADC is the internal 1.2V reference for the thermocouple measurement.
For the RTD, the internal reference or an external reference can be used (external ratiometric reference resistor is described in CN0214).
You should be able to purchase a thermocouple from any electronic catalog company (Farnell or Radionics for example)
2x thermocouples can be connected to ADC0 via the following differential channels:
ADC0/ADC1 and ADC2/ADC3
These channels have full Programmable Gain Amplifier support
3x more thermocouples can be connected to ADC1 via the following channels:
ADC4/ADC5, ADC6/ADC7, ADC8/ADC9
These differential inputs require an external differential amplifier as ADC1 does not have a PGA - see this link for options:
If I use a diff amp, why do I need 2 ADC inputs -ADC4/5, ADC6/7, ADC8/9 for 3x more thermocouples?
The ADuC7060 already has internal reference, so no need to provide additional cold junction compensation.
I was thinking of using AD595.
To clarify, ADC0 can directly support 2x thermocouples.
ADC1 can support up to 5x thermocouple inputs if an external amplifier/external differential amplifiers are used with these 5x thermocouples. ADC channels, ADC4, 6,7,8,9 can be measured in single-ended mode
For the thermocouple connected directly to ADC0, the PGA gain is set to 32. Let's say if a thermocouple has 40uV/deg C, with gain of 32, this is 1.28mV/deg C ?
Cold junction compensation is done by RTD, not the internal voltage ref?
Where can I buy thermocouples.
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