Hach Lachat BD40HT, User Manual

Page: 13 / 124

2. On the Edit tab, push NEW METHOD .
3. Use the keyboard to enter the name of the method. Push ACCEPT .
4. On the Edit tab, push Step 1 .
5. At the bottom of the Edit tab, push Other to select glass digestion tubes.
6. Refer to the written method instructions to find the necessary information.
Option Description
Time TO Temperature Range: 0 to 999 minutes. The time that the digestion block will use to get to the
temperature set point. Refer to
Find the "Time to Temperature" value on page 13.
Note: Enter a value of "1" to get to the temperature set point as fast as possible.
Time AT Temperature Range: 0 to 999 minutes. The amount of time for the method to stay at the Step
1 set point.
Setpoint Temperature The temperature is defined by the written method.
7. Repeat steps 5 and 6 for methods with additional temperature reaction periods.
Find the "Time to Temperature" value
There are two types of temperature change. The first is a temperature change from room
temperature to an initial set point (Example 1). This is usually a look-up value.
The second temperature change is for methods that have multiple temperature set points. In this
scenario, the block temperature will be above room temperature when the temperature increase is
started (Example 2). This value must be calculated.
Note: Enter "0" to keep the controller on the edit screen or disregard Step 2 or Step 3.
Example 1: Find the time to temperature value from room temperature to 250 °C. Refer to Figure 9 .
Find where the temperature rate line crosses the 250 °C line. The minimum time to temperature from
room temperature to 250 °C is about 20 minutes.
Example 2 : Increase the temperature from 250 °C to 400 °C.
1. To calculate the temperature change, subtract the first temperature from the second temperature.
The temperature change is:
400 – 250 =
150 °C .
2. Refer to Table 3 . To find the rate of temperature increase, use the row for a temperature change
of 25–200. Read the value in the column for a set point of 350+. The rate of change is:
3 °C/min
3. Use the equation Temperature change ÷ Rate of change = Time to Temperature . The time to
temperature for the second set point is:
150 °C ÷ 3 °C/min =
50 minutes .
English 13