Calcium is an alkaline-earth metal that is an important component of the cell walls of aquatic plants, and of the bones and shells of aquatic animals.
Calcium ions find their way into water as it flows over rocks that contain calcium, such as limestone and gypsum. In freshwater, the concentration of calcium ions is generally in the range of 0 – 100 mg/L.
The Calcium sensor is an Ion Selective Electrode (ISE). It tests for calcium in water by measuring the levels of charged calcium ions.
Our Calcium ion sensors come as standard on many of our probes, below are some examples.
To see all of the probes that feature calcium please visit the Products section
The Aquasonde-2000 has 2 spare ports. They can house either 1x ISE sensor and 1x Optical sensor. Or it can house 2x ISE sensor.
This is a solid state sensor in that it is not gel-filled. The advantage of this kind of sensor over those offered by other manufacturers is that the sensor will not deteriorate over time so long as it's dry.
A new, dry sensor can be stored for years without degradation. Gel-filled sensors, on the other hand, have a finite life from the point of manufacture.
Successful calibration of an ISE is fairly complex. On its initial use, a three-point calibration is required. Generally, this is at 10ppm and 100ppm of the sensor's specific calibration solution, with the third point intended to characterise the effect of temperature on that specific sensor. The third point is a second calibration at 10ppm however, this calibration point must be at least 10 degrees colder than the initial point. This is because the measured concentration varies with temperature as well as the actual concentration of the ion.
The good news is that once this calibration is complete, subsequent calibrations do not require the third point to be re-done making future calibrations much simpler to perform.
An ideal ISE sensor would only allow the ion in question to be passed through the membrane. However, in practise all ion selective electrodes suffer from interference from ions which are similar in nature to the target ion. For this reason, ISE Electrodes are not recommended for use in brackish or salt water due to the high level of interfering ions.
Installing the calcium sensor into an Aquaprobe is a very simple process. Simply unscrew the blanking plug from an appropriate aux socket, apply some silicon grease to the thread of the sensor (grease provided) and screw in the sensor. After installation full calibration is required.
If the calcium levels concentration is less than 5 mg/L, then the ability of that water body to support life is dramatically decreased. Low levels of calcium can be a factor in oligotrophy.
An oligotrophic lake or river is an unproductive one because of low nutrient content. An indicator of an oligotrophic condition is very clear water. Seawater contains calcium ions at levels of around 400 mg/L.
To use Aquaread's calcium sensor, first install it into your probe of choice, then perform a full calibration using dilutions from the stock calibration solution. Once calibrated it's good to go. Simply put the probe into the body of water, allow the reading to stabilise and take your measurement.
Calcium sensors are used for measuring calcium in water. The concentration of calcium in water is also known as water hardness. Hard water contributes to scaling in boilers and industrial equipment. Measuring calcium in water is important in industrial settings in order to prevent costly breakdowns that can be caused by limescale.
Water hardness also affects fish because it influences osmoregulation, which is their constant internal regulation of body fluid concentration. High levels of calcium in water can trigger diseases in fish. Calcium sensors can be used in fish farming to ensure the levels are maintained at an optimum place and can also be used for measuring calcium in water that is designed for drinking.