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I am currently using a KE-25 oxygen sensor which is galvano microcell type oxygen sensor which doesn't require a power supply to sense oxygen level in the environment. Depending on the concentration of oxygen % in the air it gives an equivalent voltage output.

I have to interface this sensor with PLC, but the PLC doesn't sense such mV output so I am trying to convert 0.5-75 mV to 0-10 V which can be read by my PLC.

So please help me to find out which amplifier I should use to boost mV to V.

Niteesh Shanbog
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jalath
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  • Have you tried a normal opamp? – winny Oct 15 '18 at 09:31
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    Since you are talking about a PLC, I'm going to assume this is in an industrial setting, look at just purchasing a signal conditioner from someone like Phoenix. In industrial settings, try to resist at all costs "Rolling your Own". Phoenix does have several conditioners (as do other manufacturers) that convert 0-75 mV to 0-10 V. – R Drast Oct 15 '18 at 09:57

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I suggest using a low-Vos op-amp with low input bias current, in a non-inverting configuration. The sensitivity is not well controlled on that type of sensor so you may either wish to add a trimpot or adjust the sensitivity digitally.

Input impedance must be higher than 1M ohm, which is a low bar to achieve. For example, you could use a 12V supply and an OPA189 There are cheaper amplifiers too, but since you have a PLC just about anything will look relatively reasonable.

Spehro Pefhany
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