Why would the rollers need to be geared? Or are you talking about something else?

The motor is DC brushed usually so attempting to run the pump down to a typical 3rpm is tricky, plus the motor torque is magnified by the ratio of reduction, so a small motor suffices.
Max.

 

Maybe we are talking about different things...sorry. Here is what I was referring to. In the two images, one you'll notice the shaft is straight, and the rollers just kind of wrap around the motor shaft. The other, the drive shaft has a flat side to it that the roller assembly latches on to.

 

Is that direct drive and 5krpm?
It is not the best example of a peristaltic pump construction I have seen.
Max.

 

Yeah the one on top is direct drive 5krpm, the second one is a 12v gear-boxed motor that runs at 200rpm.

 

Is that direct drive and 5krpm?
It is not the best example of a peristaltic pump construction I have seen.
Max.

The first pic is the cheap head and motor that comes with these Jebao dosing units.. Its just friction attaching the shaft to the pump head.. Thats where my comments about it could be mechanical issues came from.
The second is the other motors/heads he was planning on using.. (or maybe already has)

I didn't catch it or didn't notice if the OP already swapped out to a more reliable dosing pump/motor and was still having accuracy issues.

 

Yeah, I switched them out with a pump that's made in Japan, not the one in the picture. Here is a visual of the one I'm using.

 

So I have an inexpensive dosing pump system I purchased, its an inexpensive chinese product. The software is OK, and the pumps were mediocre at best. I had four welco pumps here at home which are very well made japanese peristaltic pumps so I thought I'd swap those into this unit. The pumps run great but even with the calibration in the software, they aren't as accurate as I'd like. So my question is, is it possible to put a very fine tuning potentiometer between the board connection and the motor so I can fine tune the speed of the motor for more accurate dosing?

Here is the doser: I Paid $60
http://www.fish-street.com/jebao_auto_dosing_pump_dp-4

Here are the pumps I put in place of the stock pumps: I have the WPM1-P2BA-WP
www.welco.net/dcms_media/other/WPM_selectguid.pdf

Any assistance would be awesome...thanks again.

Something that can actually MEASURE the flow and provide feedback to the pump mechanism would be best. A positive displacement flow meter is what you want to look for.

 

I've looked into those, they are a bit overkill for this application. Plus then I'd have to redesign the electronics, and I'm not really into that at the moment.

 

I've looked into those, they are a bit overkill for this application. Plus then I'd have to redesign the electronics, and I'm not really into that at the moment.

You can add something to change the speed of the motor as already discussed here/suggested by you .. BUT thats not doing anything different than just changing the calibration time..
So just run the calibration again and either stop it just before or just after the 100mL has been moved from container to container and you have effectively just fixed your issue.

 

You can add something to change the speed of the motor as already discussed here/suggested by you .. BUT thats not doing anything different than just changing the calibration time..
So just run the calibration again and either stop it just before or just after the 100mL has been moved from container to container and you have effectively just fixed your issue.

That's actually what I'm doing now. It does work quite well. Maybe that will be an easier fix.

 

I ran numerous tests and it seems to be good. I have each pump set to measure out 3mL, and each one pumped out 3.2-3.3mL each time. I ran the test four times on each pump and it was very consistent. I have smaller diameter tubing coming tomorrow, tubing that matches the tubing inside the pumps themselves. Hopefully that will help things out as well.

 

Isn´t 3ml quite a low amount for such size of pump? I mean, how much liquid is trapped between the two rollers - I would think that this sets the lowest possible difference in pumped volume?

 

The datasheet by Welco explains how flow rate is measured and the many variables that could change it along time.

They do not seem too worried about measuring any speed or RPM.