DDS EX
Explosion-Proof Transmitter and Controller Instruction Manual
53
Acknowledging Relays
There are two ways to acknowledge relays programmed for manual reset:
1. Via the programmable F4 digital input assigned to ACK (Default) and connected to a normally
open pushbutton wired across F4 and COM.
2. Remotely via a normally open pushbutton wired across one of the digital inputs and the +5 V
terminals on the digital I/O modules, which is triggered with a contact closure to COM, or with an
active low signal (see page8).
When the ACK button or the assigned digital input is closed, all relays programmed for manual reset are
acknowledged.
Figure 19. Acknowledge Relays with F4
Function Key
Figure 20. Acknowledge Relays with Digital
Input
Pump Alternation Control Applications (
Altern
)
For pump control applications where two or more similar pumps are used to control the level of a tank or a
well, it is desirable to have all the pumps operate alternately. This prevents excessive wear and overheating
of one pump over the lack of use of the other pumps.
Up to 4 relays can be set up to alternate every time an on/off pump cycle is completed. The set points and
reset points can be programmed, so that the first pump on is the first pump off.
Application #1: Pump Alternation Using Relays 1 & 2
1. Relays 1 and 2 are set up for pump
alternation.
2. Relays 3 and 4 are set up for low
and high alarm indication.
Pump Alternation Operation
1. Pump #1 turns on when the level reaches 30.000, when level drops below 10.000 pump #1 turns off.
2. The next time the level reaches 30.000, pump #2 turns on, when the level drops below 10.000, pump
#2 turns off.
3. If the level doesn’t reach 35.000 pump #1 and pump #2 will be operating alternately.
4. If pump #1 cannot keep the level below 35.000 pump #2 will turn on at 35.000, then as the level drops
to 10.000 pump #1 turns off, pump #2 is still running and shuts off below 5.000.
5. Notice that with the set and reset points of pump #2 outside the range of pump #1, the first pump on is
the first pump to go off. This is true for up to 4 alternating pumps, if set up accordingly.
6. Relay #3 will go into alarm if the level drops below 4.000 and relay #4 will go into alarm if the level
exceeds 40.000.
P-
F4
P+
COM V+
3
4
1
2
5
mA+ COM V+ mA+
7
8
6
9
Ack
+5
I1
I2
I3
I4
O1
O2
O3
O4
G
DO 1-4
GND
ACK
PDA1044 Digital I/O Module
1
2
3
4
5
6
7
8
9
10
DI 1-4
Set and Reset Point Programming with Pump Alternation
Relay Set Point Reset Point Function
1
30.000
10.000
Controls pump 1 & 2
2
35.000
5.000
Sets dual pump trigger
3
4.000
9.000
Controls low alarm
4
40.000
29.000
Controls high alarm
