General information on conductance measuring devices
Many conductivity meters only measure accurately at 25°C. At other temperatures, the determined value must first be converted.
For aquaristics, the change in the measured values over time is usually more important than the exact, absolute measured values. Low conductance values are often important in aquaristics. The resolution of the measurement scale is insignificant in such areas if the measurement accuracy fluctuates within too large tolerance limits. It doesn’t really matter if a device constantly displays a value that is always too high or too low by the same factor. The trend of the change is still displayed correctly. The absolute accuracy of the measuring device is therefore less important.
It is particularly disadvantageous if the tolerance range of a device is constantly being used in different directions with different sizes. The measurements then have almost no significance for aquaristics.
Empirical values and control measurements in liquids with a precisely known or always the same conductivity give indications of how suitable the measured values of the device are.
Practically all conductivity meters measure with sufficient accuracy for aquaristic purposes.
Because the measured values change over time due to the aging of the electrode and the electronic components, conductivity measuring devices must be calibrated regularly.
Conrad WA300
- measuring range 0 – 1999 µS
- resolution 1 µS; Accuracy: +/- 4% + 3 digits. The actual value can deviate from the displayed value by 4% above and below the displayed value. In addition, a three must be added to or subtracted from the last digit shown in the display.
- Two-point adjustment via zero point and sensitivity
- External probe
Greisinger GMH 3439
- Measuring range from 200 µS/cm to 200 mS/cm
- temperature adjustment
- salinity measurement
Advantages:
Disadvantages:
Hanna Dist 3
- measuring range 0-2000µS/cm.
- Internal probe
Advantages:
Disadvantages:
- Requires relatively expensive 4 silver oxide button batteries.
Milwaukee
Advantages:
- Very good resolution of xxxx times 10
- temperature adjustment