GLOBE Equipment - Hydrosphere

GLOBE Instrument Specifications

All GLOBE instrument specifications described below represent the minimum specifications necessary to collect scientifically valid data. GLOBE schools may use instruments that meet or exceed these specifications. For example, the GLOBE specifications for pH paper call for a range of 2 to 9 pH units. A pH paper with a range of 1 to 14 exceeds specifications and may be used by GLOBE schools.

Alkalinity - Middle, Secondary Skill Levels

     Instrument Specifications: Water Alkalinity Kit

Instrument Specifications: Safety Equipment

Dissolved Oxygen - Middle, Secondary Skill Levels

Instrument Specifications: Dissolved Oxygen Kit

Electrical Conductivity (for freshwater sites) - All Skill Levels

     Instrument Specifications: Electrode-type Total Dissolved Solids Tester (Conductivity Meter)

Instrument Specifications: Calibration Standard

Freshwater  Macroinvertebrates – Middle, Secondary

Instrument Specifications: Kick-net

Instrument Specifications: D-net

Instrument Specifications: Quadrat

Instrument Specifications: Sieves

Nitrate - Middle, Secondary Skill Levels

Salinity (for brackish and saltwater sites) - All Skill Levels

     Instrument Specifications: Hydrometer Method

Instrument Specifications: Salinity Titration Method - Middle, Secondary Skill Levels

Transparency - All Skill Levels

     Instrument Specifications: Secchi Disk Apparatus (for deep water sites only)

Instrument Specifications: Transparency Tube (for surface water)

Water pH - All Skill Levels

Skill Level - Primary

Skill Level - Middle, Secondary

Skill Level - Middle, Secondary

Water Temperature: - All Skill Levels

Use of Probeware

Alkalinity - Middle, Secondary Skill Levels

Instrument Specifications: Water Alkalinity Kit

A water alkalinity kit can be purchased. Teachers or manufacturers who wish to use or prepare another version should ensure that it also meets the following requirements:

•     Enables measurement of total alkalinity with an accuracy of at least 6.8 mg/L as CaCO3 (low range, under 136 mg/L), and 17 mg/L as CaCO3 (high range, above 136 mg/L).

•     Contains all chemicals and containers needed to perform the alkalinity titration, including: 1) Bromocresol green-methyl red indicator and scoop for adding the required amount to the sample, 2) sulfuric acid for titration, and method of delivering acid to sample to achieve the required accuracy, 3) measuring containers and bottles for titration. This method is described in 19th edition, 1995, a publication of the American Public Health Association, Washington, D.C.

•     Contains clear instructions for using the kit to make this measurement, based on acid titration to a Bromocresol green-methyl red end point.

•     Plastic gloves and safety goggles

Instrument Specifications: Safety Equipment

Plastic gloves and safety goggles must be used in making this measurement.

Dissolved Oxygen - Middle, Secondary Skill Levels

Instrument Specifications: Dissolved Oxygen Kit

A dissolved oxygen test kit can be purchased. Teachers or manufacturers who wish to use or prepare another version should ensure that it also meets the following requirements:

•     Enables measurement of dissolved oxygen with an accuracy of at least +/- 1 mg/L

•     Contains all the chemicals and special containers to perform this measurement based on the Winkler titration method. This method is described in Standard Methods for the Examination of Water and Wastewater, 19th edition, 1995, a publication of the American Public Health Association, Washington, DC.

•     Contains clear instructions for using the kit to make this measurement using a procedure based on the Winkler titration method.

Electrical Conductivity (for freshwater sites) - All Skill Levels

Instrument Specifications: Electrode-type Total Dissolved Solids Tester (Conductivity Meter)

This device shall measure electrical conductivity of liquid solutions using two metal electrodes separated by a fixed distance. The device shall be designed to be hand-held, and battery powered, with no electrical power cord attached. The device shall employ a method to automatically compensate the indicated conductivity value relative to changes in the temperature of the solution. The measurement range shall be at least from 0-1990 microSiemens/cm, with a resolution of 10 microSiemens/cm, an accuracy of +/- 2% full scale, and an operating temperature of 0-50 ºC. The device shall be capable of calibration using a standard solution.

Instrument Specifications: Calibration Standard

A standardized solution of KCl and water or NaCl and water that has a conductivity of between

500 +/- 0.25% and 1500 +/- 0.25%  microSiemens at 25 ºC. 

Freshwater  Macroinvertebrates – Middle, Secondary

Instrument Specifications: Kick-net

Must have dimensions of 1 m X 0.9 m, and made of 0.5 mm mesh netting. See Instrument Construction: Freshwater Macroinvertebrates for instructions on making a kick-net.

Instrument Specifications: D-net

Must be a “D”-shape with a 40 cm long base, and made of 0.5 mm mesh netting. See Instrument Construction: Freshwater Macroinvertebrates for instructions on making a D-net.

Instrument Specifications: Quadrat

Must be a square with internal dimensions of 1 m X 1 m.  Can be made from locally available materials. See Instrument Construction: Freshwater Macroinvertebrates for instructions on making a quadrat.

Instrument Specifications: Sieves

There are two sieves required:

1.  a sieve with mesh netting of 0.5 mm or smaller

2.  a sieve with mesh netting of 2-5 mm

Nitrate - Middle, Secondary Skill Levels

Instrument Specifications: Water Nitrate Kit

A nitrate kit can be purchased. Teachers or manufacturers who wish to use or prepare another version should ensure that it also meets the following requirements:

•    Range: 0 - 10 ppm NO3-N (typical water) or a range with the highest concentration greater that what is typically observed for your water body (polluted water.)

•     Smallest increment: 0.05 ppm NO3-N for the range 0 -1 ppm NO3-N; 0.5 ppm NO3-N for the range 1 - 5 ppm NO3-N; 1 ppm NO3-N for the range 5 - 10 ppm NO3-N; 2 ppm NO3-N for concentrations greater than 10 ppm NO3-N

•     Contains clear instructions for using this kit to make this measurement.

Salinity (for brackish and saltwater sites) - All Skill Levels

Instrument Specifications: Hydrometer Method

The same instrument described in Soil Particle Size will be used for this measurement.

A 500 mL clear plastic cylinder and an organic liquid-filled thermometer for use with the hydrometer are required. The 500 mL cylinder for Soil Particle Size may be used. The calibration thermometer described in Air Temperature under Atmosphere can be used for this measurement.

Instrument Specifications: Salinity Titration Method - Middle, Secondary Skill Levels

A salinity kit can be purchased. Teachers or manufacturers who wish to use or prepare another version should ensure that it also meets the following requirements:

•    Range: 0 - 20 parts per thousand (ppt)*

•    Smallest increment: 0.4 ppt

•    Method/chemistry: chloride titration

•    Approximate number of tests: 50

•    Contains clear instructions for using this kit to make this measurement, based on the chloride titration method.

*Titrator must be refillable for use in higher salinity waters.

Transparency - All Skill Levels

Instrument Specifications: Secchi Disk Apparatus (for deep water sites only)

5 m length of rope and a disk with a diameter of 20 cm. The disk shall be colored with paint or other appropriate means such that alternate quadrants of each side are black and white. The disk must be made so that it will not be disfigured or damaged by repeated immersion in water, including sea water. It must be weighted such that it remains horizontal while it is lowered by the rope in the water. See Instrument Construction: Transparency for instructions on making a secchi disk.

Instrument Specifications: Transparency Tube (for surface water)

Clear plastic tube, approximately 1.2 m long and 4.5 cm diameter with a white cap that fits securely on the end of the tube. The end cap must display a pattern consisting of alternating black and white quadrants on the side that is viewed by looking down the tube. See Instrument Construction: Transparency for instructions on making a transparency tube.

Water pH - All Skill Levels

Note: The instrument requirements for this measurement vary according to skill level. Please select the appropriate instrument for your students.

Skill Level - Primary

Instrument Specifications: pH Paper

The pH of standing water at this skill level will be measured with pH paper which can be purchased in strips or rolls. The pH paper must have an accuracy of at least ± 1.0 pH units, with a range of 2 to 9 pH units. For water samples with low conductivity the pH paper must be accurate in low conductivity levels.

Skill Level - Middle, Secondary

Instrument Specifications: pH Meter

The pH of standing water at this skill level will be measured with a pH meter. The pH meter must have an accuracy of 0.1 pH unit, and a range of pH 1 to pH 14, at temperatures from 0 ºC to 50 ºC. The device shall automatically compensate the reading when it is placed in solutions of differing temperature. The pH meter must be capable of being calibrated using at least two known pH buffer solutions: pH 4, 7, or 10.

Skill Level - Middle, Secondary

Instrument Specifications: Buffers

pH buffer solutions are required to calibrate the pH pen and meter. The buffer solutions should have a value of pH 4.0, pH 7.0 and pH 10.0.

Water Temperature: - All Skill Levels

Instrument Specifications: Organic Liquid-filled Thermometer

The calibration thermometer or digital temperature sensor described in Air Temperature under Atmosphere will be used for this measurement.

Use of Probeware: Because probeware can be different from probe to probe as well as from instrument provider to provider, it is recommended that the user evaluates the accuracy and resolution of the individual instruments compared to the protocol specifications in order to determine whether they meet GLOBE instrument specifications.