Something I use a lot when testing for Ad-Blue issues is my Refractometer. You would have seen it in my videos......simple to use and covers driver issue errors straight away.  Now I don't do inspections anymore but I also use it when I change header tanks to explain to customers why the float is stuck as the header tank is full of rust and sediment!
 
Features:
Test 4 concentration: Ethylene Glycol, Propylene Glycol, Battery Fluids, and urea concentration additive AdBlue.
Accurately measures the density of battery fluids (1.100 ~ 1.400sg)
Measures the degree of frost resistance of the coolant (-50 ~ 0°C)
Measures the degree of frost resistance cleaning fluid (-40 ~-10°C)
Measuring the concentration of urea in solution - AdBlue (30% ~ 35%)Measuring Range
Adblue: 30% ~ 35%Ethylene Glycol: -50 ~ 0°CPropylene Glycol: -50 ~ 0°CCleaning Fluids: -40 ~ -10°CBattery Fluids: 1.100 ~ 1.400sgAccuracy:
Adblue: ±0.5%Ethylene Glycol: ±5°CPropylene Glycol: ±5°CCleaning Fluids: ±5°CBattery Fluids: ±0.02sgPackage Include:
1 x Refractometer 1 x Pipette 1 x Screw Driver 1 x Cleaning Cloth 1 x English Instruction Manual
*PLEASE NOTE THESE DO NOT HAVE A BOX TO KEEP THEM IN *