Liquid Controls SP714-S2i - Manual (Page 10)

3-WIre OPen COLLeCTOr
The 3-wire Open Collector configuration translates the output signal from the turbine flowmeter’s pickup coil into a
voltage value. The output is driven by an “Open Collector” transistor. A resistor is required to “pull-up” the voltage
when the transistor is ‘off’.
To connect the SP714-S2i for Open Collector 3-Wire:
1. Remove the SP714-S2i housing cover.
2. Pull the SP714-S2i board from the housing for access to the TB1 terminal block and the S1 switches.
3. Attach proper cable glands and/or conduit connectors to the SP714-S2i, the pulse acquisition device, and DC power supply.
4. Run the wires (through proper conduit) between the SP714-S2i, the pulse acquisition device, and DC power supply.
5. Set the first S1 switch to the OFF position and the second S1 switch to the ON position.
6. Splice the resistors between
the +V leg from the DC power
supply and the signal input
leg to the pulse acquisition
device. The value of the resistor can
be determined using the information
below.
7. Wire the SP714-S2i to the
pulse acquisition device and
DC power supply as indicated
in the schematic.
8. If necessary, adjust the input
signal sensitivity (R1), activate
the diagnostic test oscsillator
(SW2), and/or check the
diagnostic operational LEDs
(D1 & D2). See page 11.
9. Coil the wires underneath the
CPU board and place the board
inside the housing, ensuring
the wires are not pinched, and
replace the housing cover.
3-WIre OPen COLLeCTOr WIrInG
S1
ON ON
1 2
GND
1
3 2 1
Signal
+V
0V Signal Ground
Position 1 - OFF
Position 2 - ON
ON ON
1 2
DC Power
Supply
Resistor (R P )
Resistor (R
I
)
Electronic Register
or
Flow Computer
Chassis GND
3 2 1
2 1
TB2
Pickup Coil Signal
TB1
INTERNAL OPERATING PRINCIPLE
Cable Shield
Three
Conductor
Shielded
Cable
Connect Chassis GNDs at pulse acquisition device only
S1
Maximum Cable Length: 1000 m (3280’)
Minimum Wire Gauge: 0.75 mm
2 (18 AWG)
• Limit total system current to 50 mA I =
• Resistor ( R
i
) Power Dissipation P =
• Resistor ( R
P
) Power Dissipation P =
Resistor Value - 3-wire TTL Sourcing
V
dc
R
P
(V
dc
) 2
R
P
(V
dc
) 2
R
i
24 VDC Power Supply: R
i
= 1200 Ω, 1 W
R
p
= 680 Ω, 1 W
12 VDC Power Supply: R
i
= 560 Ω, 0.5 W
R
p
= 330 Ω, 1 W
5 VDC Power Supply: R
i
= 270 Ω, 0.25 W
R
p
= 25 Ω, 1 W
Recommended Resistor Value (R
p
)
sP714-s2i connections
Pulse Acquisition Device Signal Signal Ground
Sponsler IT 400 TB2 (1) TB2 (2)
LectroCount
LCR-II/LCR 600
J8 (33) J8 (37)
Toptech MultiLoad TB2B (V+ any) TB2B (V COM any)
10