Photometers 

The HI96735 portable photometer is for the measurement of total hardness. Hanna's portable photometers feature an advanced optical system; the combination of a light emitting diode (LED), a narrow band interference filter, and silicon photodetector ensure accurate photometric readings every time. The Hanna exclusive CAL Check™ feature utilizes ready-made, NIST traceable standards to verify both meter validation and calibration. The exclusive cuvette locking system ensures that the cuvette is inserted into the measurement cell in the same position every time to maintain a consistent path length.

Features at-a-glance

• CAL Check™ - Allows for performance verification and calibration of the meter using a CAL Check NIST traceable secondary standard.
• GLP - Records the date of the last user calibration performed.
• Built in timer - Ensures the appropriate reaction time is used for the chemical reaction. At the end of the timer the meter will automatically take the reading. This feature ensures consistency across multiple users.
• Indexing indent on meter - The meter has an indent that allows for a lock and key fit with the cuvette cap. This ensures that the cuvette is indexed consistently (same position) in order to maintain the same path length for accurate results.
• Cooling Lamp Indicator - It is necessary to maintain a consistent temperature of the optical components in order to maintain a narrow wavelength band of light. This photometer has a cooling lamp indicator that is displayed for a short period of time before each measurement in order to allow the components to cool and obtain the highest accuracy possible.
• Error messages - Messages on display alerting to problems including no cap, over range and under range readings, and light source error.
• Auto-shut off - Automatic shut off after 10 minutes of non-use when the meter is in measurement mode. Prevents wastage of batteries in the event the meter is accidentally not turned off.
• Battery status indicator - The instrument has a battery level indicator to display reaming life as follows:
  • 3 lines for 100 % capacity
  • 2 lines for 66 % capacity
  • 1 line for 33 % capacity
  • Battery icon blinks when the capacity is less than 10 %.
• Units of measure - Appropriate unit of measure is displayed along with reading.

Total hardness refers to the presence of magnesium and calcium. Hardness from magnesium and calcium is due mainly to runoff water dissolving these salts as it flows or filters through different layers of strata. Hardness can also cause scaling of pipes in cooling and heating systems.

The HI96735 uses an adaptation of the EPA recommended method 130.1 to measure total hardness concentrations ranging from 0 to 750 mg/L (ppm) as CaCO3. When the reagent is added to samples containing magnesium and calcium, the sample will turn a red-violet hue; the greater the concentration, the deeper the color. The associated color change is then colorimetrically analyzed according to the Beer-Lambert Law. This principle states that light is absorbed by a complementary color, and the emitted radiation is dependent upon concentration. For total hardness determination, a narrow band interference filter at 466 nm (blue) allows only blue light to be detected by the silicon photodetector and omits all other visible light emitted from the LED. As the change in color of the reacted sample increases, absorbance of the specific wavelength of light also increases, while transmittance decreases.