A Sensor That Reports How Much to Trust It

WIKA has launched a family of inline sensors measuring fundamental physical properties of process fluids in real time. The DTG-30 and DTL-30 measure density and the VTL-30 measures viscosity and temperature, all built on the company's MesoScale technology using a specifically micro-machined oscillating metallic element in 316L stainless steel with no moving parts, which WIKA says minimises mechanical drift and supports long-term stability. Output is at 1 Hz, accompanied by a real-time confidence factor allowing the quality and validity of each measurement to be assessed. A BSU-30 calculation unit aggregates sensor inputs to derive secondary parameters including specific gravity and average molar mass. The sensors carry ATEX, IECEx and FM approvals for hazardous areas. Named applications include fuel quality monitoring, tracking the mixing of fuel additives, detecting misfuelling events, converting volumetric measurements into mass flow, and monitoring amine solutions in carbon capture; they are intended for integration into OEM equipment, tank trucks and industrial skids.

The confidence factor is the feature worth singling out, because it is unusual and it addresses the real failure mode of inline analysers. An oscillating-element density sensor infers density from a resonant frequency, and that inference degrades predictably under specific conditions: entrained gas, coating on the element, deposition, flow-induced vibration, or a fluid outside the calibrated range. Traditionally the sensor reports a number regardless and the operator finds out it was wrong later, which is how instruments lose credibility. A per-reading validity indicator lets the receiving system reject or weight the value, which is the difference between a measurement that degrades gracefully and one that silently lies.

The misfuelling and additive-mixing applications explain the 1 Hz output rate, which would otherwise look slow. These are transient detection problems: a tanker discharging the wrong grade, or an additive dosing pump that has stopped, are events that need to be caught within seconds of starting rather than resolved to high precision. One reading a second across a loading operation is ample, and it is a different design target from a custody transfer meter.

For anyone specifying this class of instrument, two questions are worth asking beyond the datasheet. First, what the confidence factor actually responds to — a figure that only drops when the element is fully coated is far less useful than one sensitive to entrained gas, which is the common case. Second, how the derived parameters are calculated: specific gravity and molar mass from density require a reference condition and, for gases, a compressibility assumption, and the accuracy of the derived value inherits both. The direct measurement is usually the trustworthy one, and it is worth knowing which of the numbers on the screen is measured and which is inferred.