For CN035, why  does one of CN0359 intermediate voltage electrode needing op-amp buffer, but another without buffer?

Dear Sir/Madam,

For CN0359 four-electrode conductivity meter, why should only one of the circuit voltage electrodes using buffer, but another does not need.

In addtion, when testing, we found that voltage on the electrodes have about 1V DC offset? Why?

Thanks.

Parents
  • Thanks for your reply.

    The input impedance of AD8253 is quite high and the bias current is typically 5nA, while the ADA4000-1 has 40pA bias current. Does that means pin3 can tolerate 40pA than 5nA? And why pin2 can?

    The DC offset between P1 and P5 is about 1mV by multimeter, but the voltage between P3 (after buffer) and P5 is quite high (about  1V).

Reply
  • Thanks for your reply.

    The input impedance of AD8253 is quite high and the bias current is typically 5nA, while the ADA4000-1 has 40pA bias current. Does that means pin3 can tolerate 40pA than 5nA? And why pin2 can?

    The DC offset between P1 and P5 is about 1mV by multimeter, but the voltage between P3 (after buffer) and P5 is quite high (about  1V).

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