Key points
- Conductivity, not liquid type, decides whether a magmeter works.
- Drinking water and wastewater are almost always well above 50 µS/cm.
- Demineralised, deionised and ultrapure water usually fall below the limit.
- Measure your actual liquid at process temperature.
Why conductivity matters
The meter reads a millivolt-level signal generated in the liquid. If the liquid is a poor conductor, the source impedance becomes too high for the electrodes to read the voltage reliably, and noise dominates. Electrode design and converter input impedance set the practical minimum.
Typical conductivity values
| Liquid | Typical conductivity | Magmeter? |
|---|---|---|
| Ultrapure water | ~0.055 µS/cm | No |
| Deionised / demineralised water | ~0.1–10 µS/cm | Usually no |
| Drinking water | ~50–800 µS/cm | Yes |
| Municipal wastewater | ~500–3000 µS/cm | Yes |
| Seawater | ~50,000 µS/cm | Yes |
| Hydrocarbons, oils | ≈0 | No |
| Glycol coolants | Varies with inhibitors and water | Measure first |
Values are typical ranges for orientation; always measure the actual liquid.
What to do below the limit
- Use a turbine meter for clean, low-viscosity liquids.
- Use an ultrasonic meter for non-invasive measurement.
- Use a Coriolis meter where mass accuracy matters.
- Ask Supmea about the SUP-FMC400 low-conductivity electromagnetic meter.
Related questions
Does temperature change conductivity?
Yes. Conductivity typically rises about 2% per °C for aqueous solutions, so a cold liquid may fall below the limit.
Can I measure conductivity myself?
Yes, with a handheld or online conductivity meter such as Supmea's SUP-TDS210 series.
Sources and further reading
- Electrical resistivity and conductivity (Wikipedia)
- Supmea electromagnetic flowmeter range
- Faraday's law (Wikipedia)
Product specifications quoted here are summarised from Supmea datasheets. Confirm the figures for your exact model before final design.