Coolant Testers
Distinction and Use
If a fully mixed coolant is used in a complete replacement or replenishment of the coolant system, the mixing ratio is usually accurate and does not need to be remeasured. However, if the mixing ratio of coolant concentrate and water is produced on-site, a deviation in the concentration may occur. When filling the cooling system after loss of coolant, it is not uncommon that only unmixed water or pure concentrate is added. Then the mixing ratio of the coolant is often unclear.
Both our high-quality concentrates and the associated premixes are characterized by many other important features in addition to the antifreeze effect. These include optimized corrosion protection, high resistance to cavitation and high aging stability. With a wrong mixing ratio these advantages cannot be completely or even not provided. To check if it is a correct mixing ratio, it is necessary to know the different measuring methods.
Measurement through test spindle
The measuring device used here is a spindle that measures the buoyancy of the tested coolant, which depends on the density (see Figure 1). If the mixing ratio of coolant concentrate and water changes, it also effects the density and thus the buoyancy of the fluid. The test spindle has a scale that indicates the freezing point in °C depending on the measured buoyancy. For this the spindle must be designed for the usual density ranges of the coolant and therefore can only make a statement about cooling agents based on the same base fluid. This leads to the biggest disadvantage of this simple test method, as for example monoethylene glycol-based coolants and those based on monopropylene glycol need different spindles for testing. Using a table, the coolant concentration can be read off the scale (see Table 1).
Measurement by refractometer
The refractometer is a measuring instrument that uses the principle of refraction. Here, the coolant is placed between two prisms and then exposed to a light source (see Figure 2). While the light scattering of the prisms is known, only the coolant and its mixture affect the refraction of the light. The refracted light is thrown on a scale on which the frost protection in °C can be read when looking into the eyepiece. The mixing ratio between water and concentrate results from the scale with the help of Table 1. The advantage of the refractometer is that usually several scales are shown for a specific liquid. So, it is not uncommon that with a refractometer in addition to monoethylene glycol-based coolants and monopropylene glycol-based coolants, screen cleaners and even battery acids can be tested.
On the left: scale in the lens, on the right: sprinkling of the carrier layer
| Proportion of coolant concentrate in the mixture [vol%] | Typical antifreeze of monoethylene glycol based coolants [°C] |
|---|---|
| 30 | -17 |
| 35 | -22 |
| 40 | -27 |
| 45 | -35 |
| 50 | -42 |
Table 1: Frost protection depending on the mixing ratio*
*The frost protection depends only on the monoethylene glycolcontent and cannot be improved by additives.