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My background is in electrical engineering so I am something of a novice when it comes to pneumatic systems, but I have been tasked with designing a sampling system that draws an extremely low flow at low pressure with a diaphragm pump (0.25 lpm) which is then read by a flow meter (0..1 lpm) before passing through an oxygen sensor. The trouble is that the pressure pulsations from the pump cause a very inaccurate reading at the flow meter. We have since discovered that implementing a makeshift latex reservoir between the pump and flow meter almost eliminates the problem completely, however this is not a very industrial solution. After further research I found that a similar solution in hydraulic systems is known as a hydraulic accumulator, but I can't seem to find an equivalent product for pneumatic systems. Is there some obvious solution that I am missing or does no such product exist?

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  • $\begingroup$ Try a diffuser. A roll of toilet paper would probably work fine, as would a few coffee filters. But you can buy them if you want. Try a HEPA or HE vacuum filter. If you have nasties in the gas, try stainless steel wool, rock wool, or a Supertrap exhaust kit for motorcycles. A can of sand also works pretty well. $\endgroup$
    – Phil Sweet
    Mar 5 '20 at 2:16
  • $\begingroup$ I should probably have asked about the diaphragm pump. I'm assuming it is a tiny one like a fuel pump off an outboard. Or is it a bigger one running real slow? $\endgroup$
    – Phil Sweet
    Mar 5 '20 at 2:25
  • $\begingroup$ Phil, it is a tiny 5V pump. I will try adding a vacuum filter inline, thanks. $\endgroup$
    – user108223
    Mar 9 '20 at 1:00
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There are pneumatic accumulators, but they introduce the following problem:

If you are doing a chemical assay on the material being sampled by your apparatus, adding compliance to eliminate pulsate flow usually means adding a fairly large reservoir into the flow path, so that the pulses get absorbed by the compliance of the gas inside that reservoir. This will also delay the measurements, in that the reservoir must become fully charged with the sampled gas flow before it flows to your measurement device.

I would recommend a peristaltic pump to pull your samples out of the process flow instead of a diaphragm pump. They introduce less pulsation into the sample flow.

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you can add a very flexible blader with a light ballast weight pushing it down.

You just have to change your zero datum to the new level.

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