Hach-Lange CL17 USER MANUAL - Manual (Page 36)

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Operation
Perform the procedure below to assign functions to AL1 or AL2:
1. Press the MENU key. ALARMS will be displayed.
2. Press ENTER to select ALARMS . The screen will display AL1 (or AL2), and either the
alarm set point (HI or LO), SA (System Alarm), or SW (System Warning).
3. To change the AL1 (or AL2) assignment, press ENTER again. The item to be changed
will flash. The arrow icons indicate active arrow keys. Scroll through the available
assignments. Press the
RIGHT ARROW key to change the value of the high or low
alarm.
4. Press ENTER to select the displayed assignment.
5. Repeat the procedure to customize the other alarm relay.
In addition, a selection to recall or clear warnings is available. Access as follows:
1. Press the MENU key. ALARMS will be displayed.
a. Press ENTER to select ALARMS . The resulting screen will display AL1 (or AL2)
along with the alarm set point (HI or LO), SA (System Alarm), or SW (System
Warning).
2. Scroll through the options. When the appropriate option is displayed, press ENTER .
• RECALL WARNINGS—Momentarily shows all active warnings then displays
DONE .
• CLEAR WARNINGS—Clears all resolved warnings then momentarily displays
OK.
3. Press EXIT twice when done.
5.2.3 Set the recorder output span
This menu allows the Recorder Output High and Low limits to be set and also offers the
capability to use the ON SYSTEM ALARM option to communicate an alarm condition.
Use ON SYSTEM ALARM to send a signal to the control room using the recorder output,
to drive any device being controlled to full off, or to maintain the present level if the
analyzer goes into System Alarm status and shuts off.
The CL17 is supplied with the recorder output set at maximum range. At maximum range,
a chlorine concentration of 0 mg/L provides an output of 4 mA and a concentration of 5
mg/L gives an output of 20 mA. The output span can be adjusted to bracket any portion
of the 0–5 mg/L range with the
4–20mA signal. For instance, this function can be used to bracket a lower range for
increased recorder resolution.
For example: if chlorine concentration of your sample is normally 0.5–0.7 mg/L, the
recorder output span can be set for 0–1 mg/L (where 4 mA equals 0 mg/L and 20 mA
equals 1 mg/L).
Alternatively, the output can be bracketed between 2–4 mg/L to control chemical feeds, or
the signal can be inverted by assigning a higher mg/L reading for REC LO and a lower
mg/L reading to REC HI.
Initially, select an output span that will cover the expected range of chlorine concentration
in the sample. Determine the correct minimum and maximum values by monitoring
chlorine values in your sample over time. Adjust the minimum and maximum values if
necessary, to obtain the best span for your specific application.