Pump noise, how to deal with it?

Hi!

I get noise interference from the aquarium pump (or timer?) I use to circulate water through the system. See the screen capture below from the PT-1000 sensor (red line). The spikes/noise is aligned with the timer for the pump. Any ideas how to deal with this behavior? would adding a ferrite to the pump cable help? My electrical and circuit knowledge is limited. Any ideas or recommendations are highly appreciated!! Thanks!!
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What you are showing on your graph does NOT look like EMI “noise”… it looks like actual temperature spikes.
The graph spans 10 hours, those spikes are occurring at intervals of about 3-4 per hour. EMI would show up as a small 60Hz “jitter” on the graph when you zoom into a one minute or less time span, not as a small temperature spike every 15-20 minutes.
It looks like what is actually happening is that your water temperature rises (or falls) temporarily whenever your circulation pump is running. This is either being caused by waste-heat from the pump itself heating up the water, or the water picking up (or losing) thermal energy as it is circulating through your system.
Not much you can really do about it other than have better control over the ambient temp in the room where your water tank is (air conditioning). Or run a water chiller (noisy and expensive).
If those little temp spikes are only a degree or 2, I wouldn’t even worry about it given the overall large temperature swing you are seeing over a 24-hour period… and large temp swings like that can throw off your pH readings just so you know :wink:

Just out of curiosity, are you running an air pump and aerating stones in your tank? Running an air pump can help maintain more stable water temps (and pH levels), especially if you are running an air conditioner in the room where your water tank is.

Thanks for the reply. I did not consider it to be an actual temperature swing because the reservoir is a fairly large one (15 gallons), water has a high heat capacity, and the swing is a full degree C. Besides, I was using a DS18B20 sensors without seeing this behavior. Two sensors stopped working, so I changed to the PT-1000 in the I2C line. The EC is following the same spike behavior (maybe due to the temperature compensation ?). The res is outside in a shaded location so the temperature is expected to fluctuate through day and night.

Given the previous temperature sensors were not showing that behavior I am not sure it is an actual temp variation, but will investigate further to see if that’s the case.

I do run an air pump and an ozone generator in the tank constantly to help DO levels and keep bad guys at bay given the outdoor nature of the setup.

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The fact that your setup is outdoors is yet another indicator that what you are seeing on the graph is most likely actual temp fluctuations… when the pump runs, it is pumping water through your system, and if it is outside, the water is then running through pipes and other parts of the system that are warmer than the water in the tank, thus you will see a small, yet sharp, temporary increase in temperature while the pump is running, and then the temp drops back down again when the pump is off. This could be more exaggerated/noticeable if your temp sensor is near the water return line in your tank or near the top of the tank where the warmer water rises to.
The fact that you are seeing this with the Atlas sensor means that sensor is probably more sensitive to rapid temp fluctuations then the other sensors you used previously.
The fact that your EC is also fluctuating in correlation to the water temp is another indicator that what you are seeing is actual temp fluctuations when the pump is running (water temp does change EC measurements).
Like I said, if this was EMI, you would be seeing a MUCH higher frequency of “jitter” in the graph (about 60Hz)… if the graph even showed it at all… depends on the intervals between measurements.

You’re also cutting off the Y axis, so we don’t have the ability to make an informed reply about measurement changes, because we have no idea what we’re looking at, value-wise. Do you have any redundancy in any measurement to compare different sensing devices?

I moved the sensor to a different position (further from the water return) and the measurement is stable now. Interestingly enough, the temperature followed the “peak” of the previous behavior instead of the bottom. Thanks for the tip!!

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