Xylem SPT INLINE LOW FLOW METERS - Manual (Page 3)

CONNECTIONS
Connecting to Non-Seametrics Control Devices. It is often
desirable to connect an SPX/SPT flow sensor to a PLC or indus-
trial computer board, and the sensors are well suited for this.
Typically it can be connected directly, or with a single resistor
added. The pickup sensors are current sinking (NPN) GMR
devices that require 5-24 Volts DC and 2 mA current. They
can connect directly to a PLC or computer board (See Fig. 1) if:
1. The sensor power supply on the PLC is 5 - 24 Vdc
(24 Vdc is typical).
2. The sensor power supply can provide at least 2 mA
(100 mA is typical).
3. The sensor input on the PLC can accept a current
sinking device.
4. The PLC frequency response > flow meter output
frequency.
If the PLC input only accepts current sourcing devices, a pull-
up resistor must be added (See Fig. 2). Typically, on a 24 Vdc
input a 2.2 K Ohm resistor will be effective.
Since the three-wire pickup sensors are solid state, they do
not exhibit switch bounce and can be used at relatively high
frequencies.
If the PLC is equipped with a 4-20 mA analog input module,
it is necessary to order the S- Series flow sensor with some
form of 4-20 mA transmitter. Two options are the AO55 blind
transmitter and the FT420 indicating transmitter. Follow the
connection diagrams for these products to connect to the
analog input.
Red
White
Black
Red
White
Black
Signal
+DC Voltage
Ground
Signal
+DC Voltage
Ground
Figure 1 Figure 2
Input Designed for Current
Sinking (NPN) Devices Input Designed for Current
Sourcing (PNP) Devices
2.2K Ohm Pull-up
Resistor
NPN
Device
NPN
Device
INSTALLATION, CONNECTIONS
Red
White
Black
Red
White
Black
Signal
+DC Voltage
Ground
Signal
+DC Voltage
Ground
Figure 1 Figure 2
Input Designed for Current
Sinking (NPN) Devices Input Designed for Current
Sourcing (PNP) Devices
2.2K Ohm Pull-up
Resistor
NPN
Device
NPN
Device
Figure 2
Input Designed for Current
Sourcing (PNP) Devices
NPN Device PNP Device
Figure 1
Input Designed for Current
Sinking (NPN) Devices
NPN Device NPN Device
Piping Requirements. Standard fittings are female NPT. If the
piping connected to the meter is metallic, care should be taken
not to overtighten. Straight pipe of at least five diameters
upstream of the meter is recommended. Vertical, horizontal,
or inverted (lens down) installations are all acceptable.
INSTALLATION
K-FACTOR ON LABEL
Warning: This meter has low-friction bear-
ings. Do not at any time test operation of
the meter with compressed air. Doing so
will subject it to rotational speeds many
times those for which it was designed, and
will certainly damage the rotor, shaft, and/
or bearings.
K-Factor. The meter is factory calibrated. The K-factor is
found on the label on the meter body and must be input into
the control/display for accurate reading.
Page 3