How to choose an industrial sensor: 7 criteria that decide everything
How to choose an industrial sensor for a production facility: measurement type, range, accuracy class, wetted material, power and output, operating conditions, system compatibility. With examples from Endress+Hauser, Fluke, SPM and IFM.
In short: the 7 selection criteria
Industrial sensors are chosen not by price and not by brand, but by seven parameters that determine whether the instrument works in your process. Getting one of them wrong means the device sits on the shelf instead of measuring.
- Measurement type — pressure, temperature, level, flow, vibration or dissolved concentration
- Measuring range — the working range must exceed the process range by 20–30 %
- Accuracy class — instrument error should be at least 3× smaller than the allowed process deviation
- Wetted material — ceramics, Hastelloy or PTFE for aggressive media
- Power and output — 24 V DC, 4–20 mA, HART, Profibus PA, Foundation Fieldbus, IO-Link
- Operating conditions — IP67/IP68, explosion protection (Ex ia/Ex d), temperature range, vibration resistance
- System compatibility — fit with the existing DCS/PLC, connector type, protocol, spare parts stock
Criteria 1–2: measurement type and range
Start from the physical quantity. For bearing vibration you need an accelerometer, not a pressure transmitter. For fluid conductivity, use a conductometric analyser; for turbidity, an optical turbidimeter.
Choose the range so that real operating values sit in the middle of the scale, not at its edge. An instrument running at 95 % of scale loses accuracy exactly when accuracy matters most.
| Task | Instrument type | Typical range |
|---|---|---|
| Pressure in a pipeline | Pressure transmitter, diaphragm / piston | 0–1.6 … 0–40 bar |
| Furnace temperature | Thermocouple / Pt100 | 0–400 °C / −50…+300 °C |
| Tank level | Radar level meter / hydrostatic | 0–30 m |
| Flow in a pipe | Electromagnetic / ultrasonic flowmeter | 0–500 m³/h |
| Bearing vibration | Piezoelectric accelerometer | 0–10 g / 10–1000 Hz |
| Water conductivity | Conductometric analyser | 0–20 µS/cm … 0–200 mS/cm |
Criterion 3: accuracy
The rule is simple: instrument error must not exceed one third of the allowed process deviation. If the process allows ±1 %, choose an instrument no worse than ±0.3 %.
Watch how accuracy is stated: "±0.5 % of full scale" and "±0.5 % of reading" are not the same thing, and the gap can be significant in real units.
Criteria 4–5: medium and enclosure
The diaphragm material determines chemical compatibility. For petroleum products and solvents use Hastelloy C-276 or ceramics; for food and pharmaceutical duty use PTFE with food-contact certification.
For operating conditions three parameters matter: ingress protection (IP67 for wet workshops, IP68 for pressure washing), explosion protection (zones 1/2 per GOST and TR CU 012/2011) and temperature range. Keep at least 20 °C of temperature headroom.
Criterion 6: protocol and power
In new installations 4–20 mA with HART overlay dominates: it delivers an analogue signal and digital data without changing the cable infrastructure. IO-Link suits short branches with many identical sensors, while Profibus PA and Foundation Fieldbus fit large distributed systems.
Do not forget power: mostly 24 V DC, but loop-powered instruments and 24 V bus converters exist too.
Criterion 7: serviceability in Russia
For a Russian plant, what matters in practice is not only the price of the instrument but the lead time for spare parts and the possibility of repair. Ask the supplier: is there a spare parts stock in Russia, what is the return policy, is verification or a calibration certificate issued per batch.
For critical positions, budget 3–5 % of the batch value for spares and stock reservation at the supplier.
Common mistakes
These are the most frequent and the most expensive:
- Ordering by name only, without range and accuracy class
- Ignoring the hazardous area classification
- No spare parts stock — one failed sensor stops the line for weeks
- Mixing units when ordering (mm/inch, bar/MPa, °C/°F)
- Missing Russian-language documentation, which blocks acceptance and operation