HF scientific 19998 Triple Validation Turbidimeter - 0-100 NTU - Manual (Page 24)

TVT 1 (5/02) 18
Rev. 2.6 (.pdf)
Select the correct minutes level by pressing the t or u button to change the displayed
minutes. When you have selected the proper minute’s level, press the ↵ button.
8.5 Programming the Alarms
The instrument is equipped with two relays that are designed to operate as two
independent programmable alarms. You must input three types of information to fully
program each alarm:
1. The alarm function (HI, LOW, or OFF)
2. The alarm set point (level at which the alarm activates)
3. The delay time for the alarm: the time that the set point must be exceeded prior to
alarm activation (prevents ringing in the relay)
These three items are described below.
Alarm Function: The alarms can either be turned OFF or programmed in one of two
different manners:
1. HI alarm: the relay changes state when the measured turbidity level is
higher than the programmed alarm level for a prescribed amount of time.
2. LOW alarm: the relay changes state when the measured turbidity level is
lower than the programmed alarm level for a prescribed amount of time.
Note: The relays automatically change state when an internal system failure is detected
Alarm Set Point: The level at which an alarm activates is called the alarm set point. On
the instrument, the alarm set point is designated as “S/P”. The set point is adjustable to
any valid turbidity level over the range of the instrument in steps of 0.01 NTU.
Alarm Delay Time: The alarm delay times are used to prevent ringing of the alarm
when the measured turbidity level is close to the set point. The function of the delay
times is as follows:
Delay On: The turbidity level must exceed the alarm set point continuously for at
least this number of seconds before the alarm activates.
If the delay on time is set at 5 seconds and the process turbidity exceeds the
set point continuously for only 4 seconds, the alarm will not be activated.
However, process turbidity exceeds the set point continuously for 5 seconds or
more, the instrument will activate the alarm.
Delay Off: The turbidity level must not exceed the alarm set point continuously for at
least this number of seconds prior to deactivation of the alarm.