Digital HPLC Flow Meters

Flow Meter in Use

What Digital HPLC Flow Meters Do

Digital HPLC flowmeters are used to measure the accuracy of High Performance Liquid Chromatography pumping systems in order to meet FDA and other regulations regarding installation qualification (IQ), operational qualification (OQ) and performance qualification (PQ) of equipment used in the pharmaceutical and biopharmaceutical industries as well as other analytical labs.

HPLC systems used in regulated laboratories demand accurate, reproducible column retention times for analytes. Accurate retention times depend on accurate pump flow rates. HPLC pump calibration is one of the steps in HPLC qualification and verification.  Quarterly calibration of HPLC pump flow rate accuracy is recommended by analytical instrument manufacturers.

These precision instruments are not to be likened to flow meters used on process lines measuring flow rates in, for example, thousands of gallons per minute but instead in fractions of milliliters per minute.

Why Digital HPLC Flow Meters are Popular

The answer is clear when compared to two alternative methods defined as volumetric using a finely graduated cylinder and gravimetric using a precision analytical scale. In either case a stopwatch is needed along with a technician with excellent eyesight and a high degree of patience.

For volumetric measurement, technicians begin to collect HPLC eluent in the graduated cylinder and simultaneously start the watch. When sufficient volume is collected, the technician simultaneously stops the flow into the cylinder, stops the watch, then calculates and records the flow rate in milliliters per minute.

For gravimetric, the process is similar but measured by weight of eluent captured in a tared container.

This tedious, time consuming but critical process repeats over and over until a standard deviation can be calculated. Moreover, solvent evaporation collected in a graduated cylinder or on a balance can throw off readings. Operator-to-operator variability in reading the meniscus position in the graduated cylinder has a negative impact on reproducibility.

How a Digital HPLC Flow Meter Works

FlowCal 5000 Digital HPLC Flow Meter

Contrast this laborious and error-prone approach with the FlowCal 5000 digital liquid flowmeter offered by Tovatech. Compact, portable and lightweight, it operates on the volumetric method and functions by taking repeated and accurate measurements of the time it takes a solvent to fill a small diameter tube.  These digital flow meter measurements are far more reproducible than manual measurements.

The FlowCal 5000 is positioned at the end of HPLC system being tested to receive and measure solvent as it exits the system. This enables solvent to be collected in a bottle for later disposal. The procedure is simple when compared to manual methods.

Here is a sequence of operation that typically takes less than a minute for each reading:

  1. When solvent enters the inlet pipe at the base of the flow meter the meniscus passes an optical sensor that activates a timer.
  2. When the meniscus reaches a second sensor, the timer stops, a valve opens and the tube drains.
  3. Readings are displayed on the meter’s four-digit LCD panel and recorded to six-digit printer or computer.
  4. The process repeats itself.

Measurement accuracy is ±1 percent of the reading over flow rates of 0.05 to 25 mL/minute. Consistent readings mean the HPLC pump system is operating correctly. Otherwise the system requires attention.

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We Provide Recalibration

To ensure accuracy of your flow meter, annual recalibration is highly recommended. Turnaround time for recalibration is typically 2 weeks. Rush orders available!


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How the FlowCal 5000 Liquid Flow Meter Increases Productivity

This digital liquid flowmeter does not require constant supervision. Using it frees up technicians to perform other tasks.

Because it is portable, the FlowCal 5000 flow meter can be transported throughout the lab to conduct tests elsewhere. For example, at one installation a single flowmeter is being used to service 100 HPLC systems.

In another case, a contract analytical services provider to the pharmaceutical industry transports the unit between different client locations. The spokesperson noted that flow rate measurements can be completed in less than five minutes, including the all-important data output for record keeping. This works out to a 15- to 20-minute savings in time over the gravimetric method.

Metrologists who have used the FlowCal 5000 never want to go back to manual methods!

The FlowCal 5000 HPLC Liquid Flow Meter Close-up

  • Ideal for IQ OQ PQ and troubleshooting
  • Accurate to 1% of reading with guaranteed linearity from 0.05 to 25.00 ml/min
  • Supplied gravimetrically calibrated at 1.0 ml/min. Multi-point calibration available.
  • Durable and easy to use with any HPLC model
  • Usable with all standard HPLC solvents
  • Easy diagnosis of leaking piston seals or malfunctioning check valves
  • Automatic Data Transfer via RS232 or with a new optional battery powered mini printer

3 Modes of operation:

  1. Printer Mode: liquid flow readings are displayed on the LCD and output to a printer if one is connected. A running average option is available in this mode
  2. Terminal Mode: in this mode the liquid flowmeter is controlled by the terminal or PC. Extra commands for averaging any number of readings are included.
  3. Test Mode: this mode allows the user to test the display, valve and RS232 interface and also display the calibration date.

FlowCal 5000 Specifications

  • Reading Update Time
    • 15 sec @ 2 ml/min
    • 25 sec @ 1 ml/min
    • 45 sec @ 0.5 ml/min
  • Measuring Volume - 140 μl
  • Priming Volume - 250 μl
  • LCD Display - (12.7mm)- 4 digits and 3 status symbols
  • RS232 output - (6 digits) XX.XXXX ml/min
  • Size - 5.4 x 3.0 x 1.8 inches (138 x 76 x 45 mm)
  • Weight - 320g, 12 oz
0.05-25 1% 0.5%
0.25-5.0 0.5% 0.5%

Flowmeter Stack Mount Bracket

Flowmeter Stack Mount Bracket

Your Flow Cal 5000 flow meter is shipped with the following:

  • Mains ‘wall block’ power supply with a choice of 240V 3 pin UK, 230V 2 pin European or 100V 2 pin USA/Japan.
  • RS232 input/output cable: 8way mini-din plug to PC COM port 9 pin female.
  • UKAS (equivalent to NIST) traceable single point flow calibration certificate
  • Universal mounting kit: allows free standing mount, wall mounting, ‘stack system’ mounting and bottle top mount.
  • Black plastic carrying case with foam inserts, cleaning kit and mounting kit.

Optional Thermal Printer

A miniature thermal printer for the FlowCal 5000 Digital Liquid Flow Meter will print all readings and error messages output from the flowmeter via the built-in RS232 interface.

FlowCal Flow Meter Printer

Flow Meter Thermal Printer

Printer Features:

  • Compact and stylish design
  • Easily loaded with paper
  • Built-in RS232 interface
  • Strong case design
  • Supplied with re-chargeable battery
  • Supplied with power/charger lead with Print on/off switch built-in to plug directly into the flowmeter
  • No extra power supply required – unit uses the flowmeter power supply
  • Supplied ready to work with the FlowCal 5000 liquid flow meters set to the default settings
  • Readings printed to four decimal places

Flow Meter Recalibration

The FlowCal 5000 is shipped with a traceable calibration certificate valid for one year.  To ensure accuracy of your flow meter, annual recalibration is highly recommended.  Even if your flow meter is still operating within specifications, it will be cleaned and adjusted for improved accuracy.

When you’re ready to recalibrate your flow meter contact Tovatech for instructions.  We’ll provide pricing and a few easy steps to follow.  You’ll need to ship your flow meter back to us.

Recalibration must include a calibration point at 1 mL/min.  You can request any number of additional calibration points between 0.05 – 25 mL/min.  Standard 3-point recalibration is at 0.5, 1, and 2 mL/min.

Note that recalibration includes ‘as found’ data at 1 mL/min only.  If ‘as found’ data is required at additional flow rates they must be specifically requested.

Turnaround time for recalibration is typically 2 weeks.  Rush orders are usually possible for an additional fee but don’t wait till the last minute!

Frequently Asked Questions

The flow meter is accurate to ±1.0% of the reading with a standard deviation of less than ±0.5%.

The flow meter displays 4 digits (e.g. 0.050 ml/min), but when using an RS232 interface, the readings are output to 4 decimal places (e.g. 0.0500 ml/min).

Assuming you are able to set up and maintain a constant flow rate with pure water, you can verify the calibration of the flow meter. However, the firmware is locked and you cannot make adjustments. The flow meter must be returned to Tovatech for recalibration if adjustments are needed.

No, the flow meter must be used at the end of a line at atmospheric pressure.

The principle of operation is recording the time it takes to fill a 140 μL glass tube equipped with two optical sensors. When the liquid enters the flowmeter at the bottom and begins to fill the measuring tube the meniscus passes the bottom sensor which activates a timer. When the meniscus reaches the top it activates the second sensor that opens a valve and drains the tube. The valve closes and the process repeats itself. Each new measurement refreshes the reading on the flow meter display.

The flow meter is compatible with any HPLC system operating at a flow rate between 0.05 and 25 ml/min.

The flow inlet is a 1/16 inch diameter PEEK tube and can be connected with a standard fitting for HPLC tubing.


"Prior to using the FlowCal 5000 the flow rate was measured using a volumetric flask and a timer at two flow rates (0.10 & 1.00 ml/min).

Each measurement took 10 minutes to complete, as did any additional measurements, which we sometimes needed for various reasons. This added up to approximately 30 minutes to calibrate the flow rate for each pump.

With a total of approximately 70 pumps, which required calibration yearly and after any repair, I would estimate that I was spending approximately 50 hours a year calibrating flow rate. Now, I can take measurements at both flow rates in approximately 5 minutes using the FlowCal 5000, allowing me to do my work much more efficiently. "I would also mention that using the volumetric flask method for low flow rates was not very accurate. I was using a 1 ml volumetric flask at 0.10 ml/min, so it was imprecise exactly when the liquid reached volume, because it was moving very slow. This did not typically cause calibrations to fail because the acceptable range was +/- 5%, however small variations in flow rate can cause significant chromatography variations in some studies. Using the FlowCal 5000 gives you a much more accurate measurement at low flow rates, thus avoiding these problems."

David Mason Scientist II, KCAS Bioanalytical & Biomarker Services

 “We acquired our second FlowCal flow meter about two years ago to replace an earlier model than wore out after some 12 years of service.  Our cart-mounted FlowCal 5000 serves 100 HPLC systems in our facility – all I do is wheel it to the sites, connect it and then am free to do other work while the HPLC flow rate is measured.

“That’s one of the main advantages of the FlowCal 5000 – there is no need to monitor flow rates using the time consuming graduated-cylinder-and-stop-watch method.  Other benefits include ease of use, highly accurate readings and saving time.  I encourage any technician still calculating flow rates using a cylinder and stopwatch to look into the FlowCal for improved precision and resolution.  Its operation is intuitive and easy to master.”   

Amy Furreness, metrology technician at a major pharmaceutical company

 “I’m quite familiar with the FlowCal 5000 as I used it in a previous position.  At our company it is a great traveler as we take it on the road two to three times a week to check the accuracy of dozens of HPLC systems used by our customers. 

“I’m quite familiar with the gravimetric method and all of its challenges and can say without hesitation that nothing beats the FlowCal in terms of ease of use and speed of results.  We can complete a flow analysis in less than 5 minutes including the all important data output for record keeping.  This works out to a 15 to 20 minute savings in time over the gravimetric method.”

TT, service engineer at a pharmaceutical industry service supplier

“Our Chem Engineering department has 3 Tovatech FlowCal 5000 flowmeters that we find extremely accurate.  Prior to that we used the gravimetric method but found that accuracy suffered due to evaporation.  This occurred even when we covered the beaker on the scale because of the opening required for tubing.

“I guess that in a sentence we use the FlowCal 5000 for its accuracy at low volumetric flow rates, its reliability and its ease of use.” 

JT, UCLA graduate researcher, chemical engineering