I saw this comment about floating source “So if the source is completely floating, the voltage between the ground of the instrument and the input signals may be randomly high”
What I don’t understand here how a voltage source which has no referance to ground can be randomly high. There shouldn’t be any value ?
For example thermocouple wired to differential analog input. İt is said if it nongrounded thermocouple we should be careful about common mode voltage which means voltage difference thermocouple and differential instrument ground. But I think the same with above there shouldn’t be any current from thermocouple to differential instrument since no referance exist between them. What is the point I miss here ?
What I don’t understand here how a voltage source which has no referance to ground can be randomly high. There shouldn’t be any value ?
For example thermocouple wired to differential analog input. İt is said if it nongrounded thermocouple we should be careful about common mode voltage which means voltage difference thermocouple and differential instrument ground. But I think the same with above there shouldn’t be any current from thermocouple to differential instrument since no referance exist between them. What is the point I miss here ?