Liquid Controls SP714-S2i - Manual (Page 8)

2-WIre standard
The 2-wire Standard configuration translates the output signal from the turbine flowmeter’s pickup coil into a current
value. The 2-wire Standard configuration produces an output signal using a resistor to convert the electrical current
variations into voltages. In this configuration, the power supply travels on the signal wire. 2-wire connections are
effective transmitting the signal over long distances.
To connect the SP714-S2i for 2-wire Standard:
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
ON position and the second S1
switch to the OFF position.
6. Splice the resistor onto the +V
leg from the DC power supply.
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.
2-WIre standard WIrInG
S1
ON ON
1 2
GND
1
Signal +V
0V Signal Ground
Cable Shield
Resistor (R P )
Two
Conductor
Shielded
Cable
Position 1 - ON
Position 2 - OFF
ON ON
1 2
Electronic Register
or
Flow Computer
Z input resistance
DC Power
Supply
Chassis GND
S1
TB1
INTERNAL OPERATING PRINCIPLE
3 2 1
2 1
TB2
Pickup Coil Signal
TB1
3 2 1
Connect Chassis GNDs at pulse acquisition device only
If the total system resistance in a 2-wire standard
configuration exceeds the recommended value, the
preamplifier may function irregularly as a result of
insufficient supply voltage to the terminals.
! cautIon !
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)
Maximum Cable Length: 380 m (1200’)
Minimum Wire Gauge: 0.75 mm
2 (18 AWG)
• Maximum cable wire resistance must be less than 30 Ω R
cable
= R
w
1
+ R
w
2
(both wires in cable)
• Total system resistance with +24 VDC power supply must be between 250 and 400 Ω R
system
= R
cable
+ R
P
• Maximum System Current I
max
= 90
m
A I
max
=
• Resistor ( R
P ) Power Dissipation P
Rd
=
Resistor Value - 2-wire Standard
(V
dc
) 2
Rp
V
dc
R
system
24 VDC Power Supply: R
p
= 330 Ω, 2 W
12 VDC Power Supply: R
p
= 150 Ω, 2 W
Recommended Resistor Value (R
p
)
8