Temperature Probes and Sensors

MCG 300, MCG 351, MCG 2350

Essential measurement for corrected volumes.

What It Is & How It Works

Temperature probes measure the product temperature inside a storage tank using platinum RTD (Resistance Temperature Detector) elements. As temperature changes, the electrical resistance of the platinum element shifts by a precise, repeatable amount, and the probe’s electronics convert that shift into a calibrated temperature reading. This temperature value is the second essential input, alongside level, for calculating corrected inventory volumes under API MPMS and OIML standards.

Cognesense offers two approaches. A spot temperature probe uses a single high-accuracy RTD to measure temperature at a single fixed depth. An average temperature probe uses multiple RTD elements spaced vertically through the product column. When paired with the MCG 2350 Average Temperature Converter, these elements are automatically scanned, the system identifies which RTDs are submerged and excludes vapor-space elements and then calculates a true weighted average. The result is an API-compliant average product temperature even in tall tanks with significant stratification.

Built for demanding tank-farm environments, Cognesense probes use stainless-steel housings, armored flexible hoses, spring-loaded thermowells, and wide operating-temperature ranges. Installation involves mounting the probe through a flanged nozzle or thermowell, so the sensing elements extend into the product column. Spot probes thread into a single nozzle; average probes run the full tank height. Both integrate directly with servo, radar, and float & tape gauges for digitized data transmission.

One variable that newcomers to the petroleum industry should understand: every petroleum product expands and contracts with temperature. Without accurate temperature input, volume corrections (VCF/CTL) cannot be applied, and inventory figures, custody-transfer settlements, and mass-balance reports will contain systematic errors.

Spot Probe vs. Average Probe

A spot probe captures temperature at one depth, providing a simple, rugged, low-cost measurement suitable for thermally uniform or small tanks. An average probe captures temperature at multiple heights and calculates a representative average, which is required for large tanks, custody-transfer applications, and any vessel with significant temperature layering. Spot probes are chosen for simplicity; average probes are chosen for accuracy in stratified conditions.

Choose a spot probe for uniform products, small vessels, or pressurized tanks. Choose an average probe when custody-transfer standards or temperature stratification demand multi-point measurement.

When to Choose Temperature Probes

Temperature probes are required whenever accurate inventory, custody transfer, or volume correction depends on knowing the product temperature:

Custody-Transfer and Fiscal Measurement API MPMS Chapter 7 and OIML R85 require temperature measurement for GSV/NSV calculations. Temperature probes provide the input for VCF/CTL correction.
Petroleum Terminals and Refineries Multi-product tank farms storing fuels, crude, and intermediates where temperature-driven volume changes directly affect inventory accounting and loss control.
Large Tanks with Temperature Stratification Tall fixed-roof tanks, heated tanks, or tanks receiving warm and cold product loads where a single-point reading cannot represent the bulk temperature.
High-Pressure and Cryogenic Vessels Spheres, bullets, LPG/LNG tanks, and pressurized storage where temperature gradients are steep and safety-critical.
Blending and Density-Sensitive Operations Product blending, interface monitoring, and quality control where calculated density and mass accuracy depend on precise temperature input.

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MCG 300, MCG 351, MCG 2350

Why It Excels

Applications Requiring API-Compliant Volume Correction

Platinum RTD elements deliver ±0.1 °C accuracy with factory calibration traceable to international standards, providing the temperature precision that custody-transfer volume corrections demand.

Tanks with Vertical Temperature Stratification

Multi-element probes automatically identify submerged RTDs and exclude vapor-space elements, delivering a true weighted average rather than a single-point approximation.

Harsh Hydrocarbon and Chemical Service

Stainless-steel construction, armored hoses, and spring-loaded thermowells withstand corrosive products, high pressures, and wide temperature ranges without calibration drift.

Facilities Requiring Long Service Life with Minimal Maintenance

No moving parts, no consumables, and no recalibration drift. RTD probes deliver stable performance across years of continuous service.

Integrated Tank Gauging Systems

Direct digital integration with servo, radar, and float & tape gauges eliminates separate wiring runs and provides a unified data path from tank to control room.

What to Consider Alongside Temperature Probes

Consider an alternative when:

Your primary gauge already provides integrated temperature output and the application does not require independent or multi-point measurement.
You need only a general process temperature indication, not an API-compliant tank gauging input. A standard industrial thermocouple may suffice.
The tank is small enough or product turnover rapid enough that stratification does not develop. A spot probe alone may meet the requirement.

How Temperature Probes Fit Into a Larger System

Temperature + Servo or Radar Gauge for custody transfer applications. Level and temperature are the minimum two inputs for API volume correction. Pairing temperature probes with an servo gauge or radar level gauge creates a complete custody-transfer measurement station. See Servo Level Gauges or Radar Level Gauges.
Temperature + Float & Tape Gauges and Transmitters for corrected inventory. Adding a temperature probe to a float & tape installation enables temperature-compensated volume calculations. The MCG 2000MAX or 2920 FTT converts the mechanical level reading into a digital output, and the temperature value completes the GSV/NSV correction. See Float & Tape Gauges and Float & Tape Transmitters.
Temperature + FuelsManager® for automated volume correction. FuelsManager applies tank strapping tables and VCF/CTL corrections using temperature probe data, producing real-time GSV/NSV inventory and compliance reporting. See FuelsManager®.