I´m currently building a little measurement system with, among others, a LTC2983 for measuring 20 Type K thermocouples single wired.
I have the issue, that all channels seem to have a offset of about 6 to 7 deegree. I get similar results (within 0.3 degrees) for all channels.
For the cold junction reference, I´m using a 2N3904 transistor, which seems to work accurate.
The spi communication is working fine, so I guess that the offset is caused by the layout of the pcb...
As shown in the shematics, all channels have 1k resistors in serial (signal and ground) and a 0.01uf capacitors tied to ground. the com pin is connected to overall ground
of the system. In addition, is used the SP3004-04YTG diode arrays to protect each channel.
Do you have any idea what could cause my issue?
Thanks in advance!