Calibrating a Dosing Pump without a Calibration Feature

[jservedio]

If you have a dosing pump that does not have a calibration feature (like the Bubble Magus or Jaebo), you can still calibrate your pump with a little basic math! Even better is that it doesn't take much more effort than calibrating a pump that has the calibration feature. This is something you should do periodically - maybe once or twice a year, every time you replace the head or components, or if you change fluid types - and shouldn't take more than 10 minutes per head.  You will need to complete each step for each dosing head!

 

Step 1: The Setup

Fill a small reservoir of water (anything more than 1 cup will work) that runs to the input on your dosing pump. On the output side of your dosing pump, set up an accurate measuring cup. I'm just using a Pyrex measuring cup, but if you have something more accurate like a graduated cylinder, use it! This is what it should look like:

 

 

Step 2: Prime

Make sure your pump is fully primed. That means after you get water flowing, letting it run for a full 30 seconds. Any air bubbles caught inside are going to throw this exercise off. After it's primed, make sure your measuring cup is totally empty (just pour it back into the reservoir).

 

Step 3: Get a Baseline

Set your dosing pump to run 100ml in a single dose and run it into your measuring cup. Record this number - it's your baseline. Is your baseline exactly 100ml (or close enough)? If it is, congratulations you are done and your pump was calibrated correctly. If it isn't, we are going to start calibrating. Take the number that you just got and divide 100 by it - this is going to be your starting calibration factor. For example, if you got 73ml instead of 100, your rough calibration factor would be 1.37

 

Step 4: Refine your calibration

Now we are going to attempt to get exactly 100ml of out our dosing pump by multiplying 100ml by your rough calibration factor. Using my example above, set your doser to 137ml. Now run it three times, recording exactly how much your dosing pump dosed out. Lets say you got the following doses: 104ml, 105ml, and 103ml. Looks like the original calibration factor was off and you'll need to adjust it down slightly by a little over 4ml. Since we know that the dosing pump doses out only 70% of what you set it to, we'll pick a happy-medium of a 5ml adjustment on the doser. Using my example, that would leave us with a final calibration factor of 1.32. Write this number down on a Post It and stick it to your pump - this is what you will multiply your dose by to get the exact dose!

 

Step 5: Verify

Multiply 100ml by your final calibration factor a couple of times to ensure you get exactly 100ml (or extremely close). Make sure your math is correct!

 

Using my example, if I needed to dose exactly 9ml of an additive to my tank using pump 1, I would simply multiply that number by my calibration factor of 1.32 to get 11.88, which I would round to 12ml. This is what I would set my doser to.

[patback]

fwiw, amazon has a set graduated cylinders for real accurate measurements for about 30 bucks shipped with prime.  My doser actually ended up not being accurate in the increments I needed, so rather than dilute my solutions, I used the cylinders to dose by hand the real amount I needed.  Not at all necessary, but I thought it was a good addition to my "equipment" that I Stored under my tank.