Calibration of flow devices may be critical to the safe operation of machinery or proper operation of the end application. While in some situations the flow accuracy is not critical, it may be critical for others.  Calibration services for flow meters typically take two forms; viscosity calibration and calibration of the output signal to match a specific flow range. Calibration services for flow switches typically mean adjustment of the low flow trip signal (often known as the interlock) to a precise flow at a specific viscosity.

Proteus Industries is one of the few suppliers with its own calibration lab, and includes a standard 3-point calibration service for each and every flow meter, ensuring the integrity of end application.  The 3-point calibration provides test results in the low, mid and high end of the flow range (see example calibration sheet below). This standard calibration of flow devices occurs in water at a nominal temperature of 25 degrees Celsius.   An example of a typical 3-point calibration certificate which is provided with Proteus devices is shown below;

Custom calibration for flow devices is necessary when other coolants or water additives such as glycol, is required in the application.  In these situations, the viscosity of the fluid becomes different than the water based setpoints, and calibration is recommended to the specific viscosity of the fluid being used.  Proteus Industries can calibrate to any kinematic viscosity setpoint, by emulating the viscosity characteristics with water or water/glycerol mixtures. In cases of viscosities below 1 cSt, water is heated to achieve the desired viscosity. 

Re-calibration of flow devices for critical applications should occur on an annual basis.  With vortex style devices, re-calibration is only necessary as a result of long-term drift of the electronics, which is negligible in most applications. 

In addition to customized viscosity calibration, our microprocessor-based flow devices can be programmed such that the output of the device precisely matches the flow characteristics.  This can make programming of the control system easier, or in other cases provide better resolution of the output signal.

Three levels of additional Proteus calibration services are available in our state-of-the-art calibration lab in Mountain View, California.  The additional paid for services may include;

  1. NIST-TRACEABLE Report - see . This is the National Institute of Standards & Technology which ensures device specification tolerance with a traceability report.
  2. ISO 17025 Calibration – see . This is an International Laboratory global standard providing measurements with minimal measurement uncertainty according to the technical specifications listed in the standard.
  3. Z540.3 Calibration – see Quality Magazine description. This is the highest level of calibration, normally used by United States government agencies, municipalities and military applications.  It eliminates the risk of false acceptance in the measurement of the device.

The Proteus Industries laboratory can also support a broad range of customized testing including;

• Liquid Flow Rate (0.08 to 160 kg/min) / (0.08 to 400 LPM)
• Viscosity range from 0.2 to 150cSt
• Temperature Range (Air or Liquid), from -80C to +250C, 0.01C TPW Checks
• Pressure Range (Air or Liquid), from 0 to 1500 PSIG Calibration, Burst Test 0-10,000 PSIG

You can learn more about the science behind calibration from our published articles on the subject, at the links below.         

• Cal Lab Magazine – “Calibrating Liquid Flow Instruments Beyond +5°C to +90°C” READ MORE
• Flow Control Magazine – “A flow measurement system finds alternative applications” READ MORE
• Paper – “Comparison of two Coriolis meters from +5°C to +120°C fluid temperature” READ MORE
•Paper – “Liquid Flow Rate Automation & Uncertainty – Staying Drier” READ MORE

If you are interested in learning more about our calibration services or have a specific request, we would love to hear from you.  Contact one of our technical experts at, tell us what you are looking for, and we will gladly assist.