Storing User Programs - Hach DR/2010 Instrument Manual

3.9

Storing User Programs

3. Press if you still want to erase all the data stored in all groups.
ENTER
Press to leave the erase menu without erasing any data.
EXIT
The DR/2010 Spectrophotometer stores 50 User Programs (#950-#999). If
you try to store additional methods, the instrument will beep and display:
**NO PRGM SPACE**
Programs 950 through 999 are reserved for storing user-entered programs.
In the standard technique, absorbance values of a series of standards are
measured and stored in memory and the concentration values are entered
via the keyboard.
If the absorbance and concentration values already are known, the
absorbance and concentration values may be entered via the keypad. No
standard solutions are needed.
If the type of curve and the coefficients are known, you may enter the
curve directly by entering the coefficients.
The maximum number of data points that can be entered for a method is 45.
Note: The Constant On mode is recommended when creating a user-entered
method. In Momentary mode, the instrument turns off automatically if no key is
pressed for the user-selected time period (in Setup Menu) resulting in the loss of
any data points or edits entered.
Before entering a calibration, determine the optimum wavelength, timing
sequences (if any) and workable range of the program. Use the Sample
User-Entered Calibration Worksheet in the back of this manual to create a
user-entered method and provide documentation for future reference.
Calibration curves may have positive or negative slopes, but they must be
based on absorbance (% transmittance not allowed). The user has the
option to force the curve through 0,0 (origin) as part of the calibration.
It is important that the standards adequately describe the curve over the
range of interest. Because calibration curves may not necessarily be a
straight line, it may be necessary to prepare a preliminary curve using
many data points (standards). You may print this calibration curve for
review using the optional Citizen PN60 printer (see section 3.7.4).
If the curve is linear, only two concentration data points are needed. For
example, a standard with a zero absorbance and a standard with 1.000
absorbance are appropriate. If the curve is nonlinear, additional data
points are needed to achieve good accuracy. Up to 45 data points can be
entered for a single calibration curve. Figure 18 illustrates why additional
data points are necessary to adequately describe nonlinear curves.
59