Using our Acoem Dynoptic DSL-220 MkIII Opacity Monitor as the example, the single analogue output is a continuous signal between 4-20mA with a maximum measurement range of 0-100% opacity.
The 4-20mA analogue output is fully scalable within this range using the analogue high and low boxes as shown below. The pair of digital relays will show as either open or closed, depending on the status of the relay.
Analogue Outputs
Within the software’s Outputs tab, the operator can adjust settings for the single 4-20mA analogue output which relates to the opacity reading.
- Analogue Low – Represents the lowest scale point of the 4-20mA analogue output, set the value to the % reading which should generate 4mA
- Analogue High – Represents the highest scale point of the 4-20mA analogue output, set the value to the % reading which should generate 20mA
- 4-20mA Output – The figure shown in this box is a calculated indication of the expected mA output based on the instantaneous opacity reading.
Digital Relays
The DSL-220 MkIII features 2 x 0-3A digital relays, one is a Service Relay and the other an Alarm Relay. The utility software allows the operator to easily configure the two relays, a graphical image indicates whether the position of the relay is open or closed.
- Service – This relay will go into an alarm condition if the instruments self-checking feature identifies a fault, the fail safe setting for this relay is closed which indicates ‘no faults’.
- Alarm – This second relay is the measurement reading alarm, activated when the reading exceeds the set threshold value. This alarm relay can be delayed by setting the delay option as below.
- Threshold – This parameter defines the measurement reading at which the alarm relay will trip.
- Delay – A delay can be applied to activate when the measurement threshold value is exceeded, this delay will temporarily stop the alarm activating and the relay state changing.
The above settings are configured during the setup and commissioning process of the DSL-220 MkIII opacity monitor and more information can be found in the Operators Manual.