Hanna Instruments Digital Seawater Refractometer

Measuring salinity of marine aquariums does not get any easier OR faster than this! Now professional measurement is as simple as dripping sample water onto the prism surface and pressing the READ key. In less than 2 seconds, this outstanding precision device will display the results in clear, digital numbers on the LCD screen. Dual-level LCD shows measurements in Practical Salinity Units (PSU), Salinity in Parts Per Thousands (PPT) or Specific Gravity S.G. (20/20). Automatically compensates for temperature for accurate research-grade analysis. Rugged, water-resistant unit boasts compact design and operates on a 9V battery (included) for wire-free portability. Features low battery-life indicator and shuts off automatically after 3 minutes of non-use to preserve battery life. Digital Seawater Refractometer measures only 7-1/2" x 4" x 2-5/8" high.

Specifications

Please click on "More Information" for calibration and measurement procedure.

1. Press the ON/OFF key, then release. Two instrument test screens will be displayed briefly; all LCD segments followed by the percentage of remaining battery life. It will briefly display an indication of the measurement units set. When the LCD displays dashes, the instrument is ready.
2. Using a plastic pipette, fill the sample well with distilled or deionized water. Make sure the prism is completely covered. Note: If the ZERO Sample is subject to intense light such as sunlight or another strong source, cover the sample well with your hand or other shade during the calibration.
3. Press the ZERO key. If no error messages appear, your unit is calibrated.
4. Gently absorb the ZERO water standard with a soft tissue. Use care not to scratch the prism surface. Dry the surface completely. The instrument is ready for sample measurement. Note: If instrument is turned off, the calibration will not be lost.

Measurement Procedure
Verify the instrument has been calibrated before taking measurements.

1. Wipe off prism surface located at the bottom of the sample well. Make sure the prism and sample well are completely dry.
2. Using a plastic pipette, drip sample onto the prism surface. Fill the well completely. Note: If the temperature of the sample differs significantly from the temperature of the instrument, wait approximately 1 minute to allow thermal equilibration.
3. Press the READ key. The results are displayed in unit of interest. Note: The last measurement value will be displayed until the next sample is measured or the instrument is turned off. Temperature will be continuously updated. Note: The "ATC" tag blinks and automatic temperature compensation is disabled if the temperature exceeds the 0-40 °C / 32-104 °F range.
4. Remove sample from the sample well by absorbing with a soft tissue.
5. Using a plastic pipette, rinse prism and sample well with distilled or deionized water. Wipe dry. The instrument is ready for the next sample.

To Change Measurement Unit
Press the RANGE key to select measurement units. The instrument toggles between the three measurement scales each time the key is pressed and the primary display indicates "PSU," "PPT," and "S.G.". When the instrument displays the screen with 4 dashes, the instrument is ready for measurement. A number on the display indicates the selected unit: "1" denotes PSU, "2" denotes PPT and "3" denotes Specific Gravity.

To Change Temperature Unit
To change the temperature measurement unit from Celsius to Fahrenheit (or vice versa), follow this procedure.

1. Press and hold the ON/OFF key continuously for approximately 8 seconds. The LCD will display the "all segment" screen followed by a screen with the model number on the primary display and the version number on the secondary display. Continue pressing the ON/OFF key.
2. While continuing to hold the ON/OFF key, press the ZERO key. The temperature unit will change from °C to °F or vice versa.

Error Messages

Battery Replacement
To replace the instrument's battery, follow these steps:

• Make sure the instrument is off.
• Turn instrument upside down and remove the battery cover by turning it counterclockwise.
• Extract the battery.
• Replace with a new 9V battery making sure to observe polarity.
• Insert the back battery cover and fasten it by turning clockwise to engage.

Measurement Guidelines

• Handle instrument carefully. Do not drop.
• Do not immerse instrument under water.
• Do not spray water to any part of instrument except the "sample well" located over the prism.
• The instrument is intended to measure seawater solutions. Do not expose instrument or prism to solvents that will damage it. This includes most organic solvents and extremely hot or cold solutions.
• Particulate matter in a sample may scratch the prism. Absorb sample on soft tissue and rinse sample well with deionized or distilled water between samples.
• Use plastic pipettes to transfer all solutions. Do not use metallic tools such as needles, spoons or tweezers as these will scratch the prism.
• Cover sample well with hand if measuring in direct sun.

General Information

Designed for Research Grade Analysis
HANNA's Seawater Digital Refractometer (HI 96822) is a rugged portable, water resistant device that utilizes the measurement of the refractive index to determine the salinity of natural and artificial seawater, ocean water or brackish intermediates. The Seawater Digital Refractometer benefits from HANNA's years of experience as a manufacturer of analytical instruments. This digital refractometer eliminates the uncertainty associated with mechanical refractometers and is rugged and portable enough to be used at home, in the lab and out in the field.

The Seawater Digital Refractometer is an optical device that is quick and easy to use. After a simple user calibration with distilled or deionized water, a seawater sample can be introduced into the sample well. Within seconds, the refractive index and temperature are measured and converted into one of three popular measurement units: Practical Salinity Units (PSU), Salinity in Parts Per Thousand (PPT), or Specific Gravity (S.G. (20/20)). All conversion algorithms are based upon respected scientific publications using the physical properties of seawater (not sodium chloride). Temperature (in degrees Celsius or Fahrenheit) is displayed simultaneously with the measurement on the large dual level display along with icons for Low Power and other helpful message codes.

Key Features Include:

• IP65 waterproof protection
• Automatic Temperature Compensation (ATC)
• Battery operation with Low Power indicator (BEPS)
• Automatically turns off after 3 minutes of non-use

Specifications

Temperature Compensation: Automatic between 0 and 40 degrees Celsius (32-104 Fahrenheit)
Measurement Time: Approximately 1.5 seconds
Minimum Sample Volume: 100 µL (cover prism totally)
Light Source: Yellow LED
Sample Cell: Stainless Steel ring and flint glass prism
Case Material: ABS
Enclosure Rating: IP 65
Battery Type/Life: 1 X 9V/5000 readings
Auto-Off: After 3 minutes of non-use
Dimensions: 19.2(W) x 10.2(D) x 6.7(H) cm
Mass: 420 gram

Principle of Operation
Salinity determinations are made by measuring the refractive index of seawater. Refractive Index is an optical characteristic of a substance and the number of dissolved particles in it. Refractive Index is defined as the ratio of the speed of light in empty space to the speed of light in the substance. A result of this property is that light will "bend," or change direction, when it travels through a substance of different refractive index. This is called refraction. When passing from a material with a higher to lower refractive index, there is a critical angle at which an incoming beam of light can no longer refract, but will instead be reflected off the interface.

In the Seawater Digital Refractometer, light from an LED passes through a prism in contact with the sample. An image sensor determines the critical angle at which the light is no longer refracted through the sample. Specialized algorithms then apply temperature compensation to the measurement and convert the refractive index to: PSU, PPT or S.G. (20/20). PSU is defined as a definitive salinity-conductivity ratio relationship. It is based upon the work of the UNESCO, ICES, SCOR and IAPSO. This information is published in The Joint Panel of Oceanographic Tables and Standards. PPT (10-3) is an older used salinity scale where salinity is defined by "the salt content is the weight of the inorganic salts contained in 1 kg of seawater if all bromide and iodide are replaced by an equivalent amount of oxides" (Knudsen, 1901). Specific Gravity (20/20) is based upon the published relationship between density at 20 °C and the mass of the dissolved salts in the seawater sample (CRC Handbook of Chemistry and Physics, 87th Edition).