If you performed a hygroscopic moisture test on your hydrometer sample, enter the test weights into the Hygroscopic moisture box.
- The Container ID field is used if you've entered container weights and IDs into the program's container list: Rather than entering the weight of the container that you used for the hygroscopic moisture test, you can enter the ID of the container LabSuite will look up the corresponding weight. Container ID is not enabled unless you've selected
tare IDat the Container weights are entered as prompt on the program's Setup dialog (Options > Program Setup then click on Data Entry in the left-hand navigation panel).
- LabSuite will assume zero percent hygroscopic moisture uptake if you do not enter any hygroscopic moisture data.
Hydrometer specifications
152H
Check either 151H or 152H, depending upon the type of hydrometer used for your test.
In almost all cases, the default values given for the equation should be accepted as-is. Before modifying these values, consult D422's Diameter of Soil Particles calculation section (currently Section 15), and the program's Technical Documentation chapter.
- The default values for a 151H hydrometer are
L =16.294964-0.2645*Rm
The default values for a 152H hydrometer are
L =16.294964-0.164*Rm
Hydrometer test temperature corrections
D7928 requires the correction of hydrometer readings to account changing temperatures (which alter the density of the test fluid), as well as for the height of the meniscus.
Single-point (automatic) temperature correction
Multi-point (linear regression) temperature correction
ASTM D422 specifies that hydrometer readings are to be corrected for differences due to temperature, meniscus, and dispersing agent specific gravity: A graph of correction vs. temperature is prepared and each hydrometer test reading is adjusted based on the correction value read off the graph at the test fluid temperature.
LabSuite also offers an alternative to ASTM's multi-point correction procedure: If you take a single correction measurement at a fluid temperature of 20° centigrade, LabSuite can use a standard formula for the change in fluid density as a function of temperature to determine appropriate correction values at other temperatures.
- To use the ASTM D422 correction procedure, select Multi-point (linear regression) temperature correction. You'll be asked to enter up to six hydrometer readings and the corresponding temperature (in °C) of the fluid at each reading.
- To use LabSuite's single correction point procedure, select Single-point (automatic) temperature correction. You'll be asked to enter a correction measurement taken at a fluid temperature of 20° centigrade.
- Hydrometer correction readings should be taken from the top of the meniscus using the liquid solution (without soil!) that will be utilized for the actual test.
- Hydrometer correction values are the negative of the readings that you take (e.g., if your reading was 6, enter -6).
- Corrections for 151H hydrometers should be entered as the number of thousands; e.g.,
-6.0instead of-.006.
This value is the height of the meniscus, and should be 0 if all hydrometer test readings were taken at the bottom of the meniscus; otherwise, it should be a positive number indicating the height of the meniscus in hydrometer gradations (e.g., for 152H, usually between +.5 and +1). For the 151H hydrometer, make sure to enter the correction as the number of thousands (e.g. 0.3 instead of 0.0003).
Technician, test remarks, and test date
These items are optional. Note that, if you enter a Technician, LabSuite will automatically add the name to a popup selection list of technicians.
The hydrometer test readings grid
For each hydrometer reading, enter the elapsed time (in decimal minutes; e.g., 1 minute thirty seconds should be entered as 1.5), the temperature (in °C) and the hydrometer reading. 151H readings should be entered as the number of thousands (e.g. if the reading is 1.0279, enter it as 27.9).
- Use the Enter key to change between cells on the grid; e.g., after you've typed in an elapsed time, press Enter to jump to the temperature column.
- After you've typed in the elapsed time, you can skip entering the fluid temperature if it's the same as the temperature on the row above the one on which you're typing: press Enter twice to skip the temperature column.