Calibration of flowmeters at The National Laboratory

Purpose

The national laboratories are responsible for maintaining the national reference standards for each measurement quantity and spreading metrological competence and traceability to industry and society at large. The national reference standards are the highest level of traceability in Sweden.

A calibration performed at a national laboratory fullfils all typical traceability and accreditation requirements that commonly exist in industry and society at large. 

Method

Each type of meter requires its own calibration method and equipment. The National Laboratory för Volume and Flow has about ten measurement equipments to be able to calibrate different types of flowmeters.

Calibration of the entire signal chain

When calibrating it is impotant that the output signal (for example the pulse, the flow or the current display device) that are used normally, also is the one that is being calibrated. Output signals can go through separate amplifiers or converters and they can have different time constants and different zero suppression. Because of that, it is very important that the whole signal chain is calibrated. By calibrating, the error of the flowmeter's display can be determined.

Different flowmeters requires different calibration methods

Each type of meter requires its own calibration method and equipment. Questions regarding the choice of method and equipment include the following:

• type of meter (resolution, type of output signal, integration time, etc.)
• type of liquid (density, viscosity, aggressiveness, temperature, pressure, etc)
• mode of use (continuous operation, dosing volume, installation, etc.)
• accuracy (which measurement uncertainty to be accepted)

We have about ten measurement equipments to be able to calibrate differnet types of flowmeters

To be able to meet different requirements of calibration, we have calibration resources in the form of about ten different types of measuring equipment, several of which are fully or partly self-developed. As a national laboratory, RISE is responsible for the national standards, which means that our measurements are directly traceable to these standards.

Measuring range overview

Liquid                             Min-Max. flow rate (m³/h)              Temp. (⁰C)

Water                                                    0,03-720                                  20... 90

Water                                                    0,006-24                                  10... 90

Exxsol D40 ("Gasoline")              0,00006-150                          ca 20

Exxsol D120 ("Diesel")               0,0006-300                            ca 20

Motor-/hydraulic oil                     0,03-25                                      20... 60

Oil, spirit, glycol etc.                     0,0006-1,2                             ca 20   

Note that the values in the table are approximate.

Deliveries

The calibration results are reported in a digital calibration certificate in Swedish or English which states that the calibration was performed at a national laboratory.