Five Star DEF’s Lab Part 2: Our DEF Quality Equipment

Oct 11, 2013

Digital Scale

We weigh technically pure urea for each of our products. For our initial product offering that makes 1.36 gallons of DEF, 4.050 lb* (1837 g) of pure urea is weighed using our Intelligent Weighing Technology PC 6001 Digital Scale.

5 Star DEF measures each portion of technically pure urea for Basic and Refill Kits. We calibrate our scale before each daily production batch using our 5000 g calibration weight.

The accuracy required to guarantee urea content quality 31.8 % to 33.2% per ISO22241 using a typical 1 gallon container of pure water from a commodity store is +/- 9g (.02 lb). Our weighing accuracy is +/- 1 g.

Here are the manufacturer’s accuracy specifications for our digital scale:


6,000 g / 13.2 lb / 210 oz / 30,000 ct

Readability 0.1 g / 0.001 lb / 0.001 oz / 0.5 ct 
Repeatability (Std. Dev.) ± 0.2 g 
Linearity ± 0.2 g

*Why 4.050 lb? Simple: This mass of urea guarantees a minimum urea content of 32.0%, with a nominal value of 32.5%. The average mass of water in a grocery gallon is 8.41 lb based on measuring over 50 bottles from various grocery stores.

Digital Refractometer

We measure urea content in DEF an average of 10 times per week. We test DEF that we make, we test DEF from other manufacturers, and we test DEF that we sample from our vehicle’s tank. We test DEF that we are exposing to real world storage requirements in our custom made thermal test chamber. We have made 100’s of measurements using our MISCO-DEF-201 Refractometer.

5 Star DEF measures urea content of each production verification sample.

We make at least 2 1.36 gallon DEF quality verification samples from each production lot of technically pure urea that we buy (2000 – 10,000 lb). We make these samples using the exact same materials and conditions that our customers do. We use this DEF in our F350. We purchase gallon containers of distilled water from the local grocery store. The first sample is made from the first unit of the production run, and the second sample is made using a refill of urea and the container from the first batch. Then we test urea content using this instrument. We conduct 1 point calibration of our refractometer before each day that we use it

The Misco DEF-201 meets the ASTM D7821 Standard Test Method for Field Test Determination of Urea Concentration in Diesel Exhaust Fluid (DEF). ISO22241 quality requirements specify refractometer test repeatability of .1% and reproducibility of 1%.

Here is the spec sheet:

Scale Fluid Name Unit of Measure LCD Display Name Range Resolution Precision
185 Urea (NH2)2C0 %Weight / Weight Urea % wt 0-50 0.1 0.1


We measure density of DEF made with our Kits. Density of DEF is a key indicator of urea content. The integral thermometer provides an accurate temperature measurement required to correct the density reading to standard conditions.

5 Star DEF Measures the density of each production verification sample.

The Chase 7820L (ASTM 309HL) meets the ASTM E-100 Standard Specification for ASTM Hydrometers. Density measurement accuracy is .5 or less when corrected for temperature. ISO22241 Quality requirements specify a hydrometer density test with repeatability of .5 and reproducibility of 1.2.

Here is the spec sheet:

Product Type Thermo-Hydrometer
Class Density (Kg/M3), ASTM 309HL
Range 1050 to 1100 Density (Kg/M3)
Resolution 0.5
Temperature Range -20 to 65°C Thermometer (Mercury)
Temperature Resolution
Length 380 mm, 15 in
Calibration Calibrated @ 15°C

More details of our lab on my next post… Five Star DEF’s Lab Part 3: Our Water Quality Equipment.

Erich and Kathryn are retired engineers with over 65 years of combined experience in engineering, manufacturing, and management. They started Five Star DEF to help families like them who travel and use DEF for their trucks and campers.