Electro-Chemical Devices (ECD) HYDRA Ammonium - Manual (Page 24)

Page 16 HYDRA NH
4
+ -N
value which forces an automatic sign change. The Off value is the hysteresis point that the PV has to
correct to before the relay disengages.
3.4.2 One AC10 with Two HYDRAs
When two HYDRA Analyzers are connected to one AC10 Air Blast Spray Cleaning System then one C22
Analyzer becomes the MASTER and the other C22 Analyzer is a SLAVE.
3.4.2.1 Master Configuration
Relay 1 is configured as a high alarm triggering at 10.0 ppm NH
4
+ -N. The value can be changed in the Set-
Up Menu as shown in Section 3.2.6. Changing the > sign to a < sign in the On line changes the set point
from a high to a low alarm. This can also be accomplished by setting the Off value higher than the On
value which forces an automatic sign change. The Off value is the hysteresis point that the PV has to
correct to before the relay disengages.
Relay 2 is configured to trigger the Digital Input (Aux In) of the SLAVE analyzer. This initiates the Manual
Mode function of the SLAVE analyzer, placing the mA outputs in a Last Value Hold (Bumpless).
Relay 3 is configured to control the Air Blast Spray Cleaner. It is triggered by Timer 1. Timer 1 is
configured as a periodic timer. The default setting (Set Up Menu) for the period is 15 minutes with the
duration set at 30 seconds. This triggers a cleaning cycle every 15 minutes alternating between the
MASTER and the SLAVE units, so each HYDRA sensor is cleaned every 30 minutes. (see Relay 4
below)The period and duration of the cleaning cycle is user configurable and dependent on the
application. For water going to the clarifier an adequate cleaning cycle may be, every two hours for 15
seconds, where incoming water to an aeration basin may require a 30 second cleaning cycle every 15
minutes.
The Now clock is an arbitrary timer. The Period determines the amount of time that must pass before
the Now clock resets to 00 hours, 00 minutes and 00 seconds, 00: 00: 00. The On time is the start time
and it is set at 00: 00: 00, so every time the clock resets Relay 1 is triggered. The Off time sets the
duration of Timer 1 and is set at 00: 00: 30, thirty seconds. (See Section 3.2.6 above)
To Change how often the Spray Cleaner actuates, change the Per line to ½ the desired period. The
display is set for days, hours: minutes: seconds, 0d00: 00: 00.
To Change the duration of the Cleaning cycle change the Off line. If the duration is changed from the
default value of 30 seconds then the Manual Mode Timer should be adjusted to allow the sensor to
stabilize after the cleaning cycle. Adjust Timer 2; Off line; to the new Clean Time (CT) + 1 minute.
Relay 4 is configured to control the diverter valve which alternates the Air Blast between the two
sensors. It is triggered by Timer 2. Timer 2 is configured as a periodic timer. The default setting (Set Up
Menu) for the period is 30 minutes with the duration set at 30 seconds. The Period of Timer 2 must be
twice the Period of Timer 1 and have the same duration.