How to Dispense a Fixed Volume with a Basic Speed-Control Peristaltic Pump

A basic speed-control peristaltic pump usually does not have a built-in dosing function. In many cases, you can only set the pump speed and control how long the pump runs.

However, you can still dispense a fixed volume by calculating the required RPM based on the pump head, tubing size, target volume, and running time.

Information You Need Before Calculation

Before calculating the speed, you need to know the following:

• Target volume per run — for example, 120 mL.
• Speed range of the pump drive — such as 0.1–600 rpm or 0.1–350 rpm, depending on the model.
• Pump head specifications — including supported tubing sizes and the volume delivered per revolution (mL/r).
• Expected running time — for example, 10 seconds per dispensing cycle.

The Calculation Formula

The key parameter is mL/r — how many milliliters the pump delivers per one full revolution.

If your running time is in seconds, convert it to minutes first:

Example: Dispensing 120 mL in 10 Seconds

Let’s say we are using a BT300N drive with an EasyPump I pump head, 17# tubing, targeting 120 mL per cycle in 10 seconds.

According to the pump head specification, 17# tubing delivers approximately:

Convert 10 seconds to minutes:

Calculate the required RPM:

Set the pump to 216 rpm and run it for 10 seconds to dispense approximately 120 mL.

Prime the Tubing Before Dispensing

Before starting the actual dispensing process, make sure the liquid has completely filled the tubing.

When the pump is used for the first time, or after changing tubing or liquid, there may be air inside the tube. If you start timing immediately, the pump may spend the first few seconds pushing air instead of liquid, causing the first dispensed volume to be lower than expected.

Manually run the pump until liquid flows steadily from the outlet with no visible air bubbles, then begin the timed dispensing cycle.

Check Whether the RPM Is Within the Pump’s Range

After calculating the required RPM, always verify it falls within the speed range supported by your pump drive.

If the calculated RPM exceeds the drive’s maximum speed, increase the running time to reduce the required RPM. For example, extending the run from 10 seconds to 20 seconds for the same 120 mL target reduces the required speed from ~216 rpm to ~108 rpm.

Why Calibration Is Important

Manufacturer flow rate and mL/r data is typically measured using water under standard test conditions. If you are pumping a different liquid, actual output may vary.

Factors that affect dispensing accuracy include liquid viscosity, tubing material, tubing wear, suction height, outlet pressure, and back pressure.

For better accuracy, measure the actual output and calculate your own mL/r value:

Alternatively, run the pump at a fixed RPM for a fixed time, measure the output, then calculate:

Summary

A basic speed-control peristaltic pump can be used for fixed-volume dispensing as long as you know the tubing output per revolution, set the correct RPM, and control the running time accurately.

For best results: prime the tubing before dispensing, confirm the calculated RPM is within the drive’s speed range, and calibrate the actual mL/r value when pumping liquids other than water.