EGT/CHT gauge "thermocouple error"

[Shack 25PS]

Researching EGT/CHT combo gauges and the Westach units look nice, but Westach mentions that their gauges are calibrated to 75deg. If I read their manual correctly, when current OAT deviates from 75, their gauges are in error. So on a 90 deg day, the indication is off by 15deg. On a cold 30deg day, the error would be 45deg!

Is this commonplace with all simple, non-powered CHT/EGT gauges?

Or do other manufacturers correct indications using current OAT?

 

[TFF1]

 

[crankyklingon]

 

[Shack 25PS]

 

[Dana]

 

[Shack 25PS]

 

[larryM]

 

[Shack 25PS]

 

[PittsDriver68]