offset problem of AD8629 OPAMP

Dear Sir/Madam,

Our customer have met one trouble as following.

(This discuss came from another sled cause my miss understood)

On my enclosed schematic Fig-1.pdf,

step-1 power off and keep waiting around 30 sec

step-2 power on

step-3 around 90msec offset voltage appear at out-1 pin

step-4 power off and on but the 90mV offset is not cleared

Also refer to my enclosed time chart "tme chart when power off and on.pdf".

note

*1 ; 30sec is not certainly.

*3 ; in some cases, it return to expected value

After once this trouble happen, out-2 is up and dowm on offset voltage 900mV(x10 gained value)

 

When we work with above action, does your AD8629 do such a motion?or not.

If he replace the thermopile(TP) to fixed resister 175kohm, then the result was same.

Please advice us before your holiday!!

Thank you in advance Kaos

attachments.zip
Parents
  • Hello Harry – attached is the amplifier schematic.

    The amplifiers on the schematic were changed from AD8629 back to AD8552s until we resolved the problem.

    The thermopile spec is embedded in the pdf.

    It is made by Heimann: HTS E21 F3.91/4.26/180.

     

    Thanks!

     

    Bruce Cardoza

    EMERALD INSTRUMENTS

    T: (604) 937-3570

Reply
  • Hello Harry – attached is the amplifier schematic.

    The amplifiers on the schematic were changed from AD8629 back to AD8552s until we resolved the problem.

    The thermopile spec is embedded in the pdf.

    It is made by Heimann: HTS E21 F3.91/4.26/180.

     

    Thanks!

     

    Bruce Cardoza

    EMERALD INSTRUMENTS

    T: (604) 937-3570

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