GHL Doser accuracy

[janvh001]

I have 2 pieces of GHL Dosers 2.0 with 4 pumps each.

I want to use 1 doser for the KH Director and started calibrating the 3 pumps according to the manual (2 pumps at speed 3, 1 pump at speed 0)
I calibrate by using a precision weight scale (0.01g) and rodi water.
For each pump I do 3 calibrations and enter the volume/minute if the 3 calibration results are the same.

The pump at speed 0 seems to be correct.
But the 2 pumps at speed 3 have a bit of fluctuations when set to pump 80ml. There are differences of 1 to 2 ml.
Is this according to the accuracy of these pumps? Or should the pumping volume be exact 80ml?

I cannot improve much to the set up.
Suction hose length is 25cm. Pressure hose length is 15cm.

[Vinny]

What is the firmware version of both 2.0 dosers?

[janvh001]

The current version is 33.
I am just wondering what the expected accuracy would be for a speed 3 and volume of 80ml.

If you can confirm that, I can further see how to improve the set up.

[Vinny]

A tolerance of +/- 0.5ml is acceptable.

Perhaps the parts (head, tubing, rollers) are due for replacement due to age. That will certainly cause accuracy issues if the parts are worn down.

[janvh001]

Thank you Vinny.
I will order some motors and tubing as these pumps already have some years of running hours.