Aalborg PWM Paddle - Manual (Page 7)

4
CAUTION: Never use compressed air or gases to test the meter, as this
would damage the Bearings. ƽ
5. INSTALLATION
PWM Paddle Wheel Meters are available with or without optional RTD (Resistance
Thermometer Device) probes. NPT female inlet and outlet port sizes are shown in the
table in the flow rate on the preceding page.
It is necessary to include an upstream straight pipe of at least five times the inside
diameter of the line.
Installation horizontally or vertically is acceptable.
The magnetic sensor requires 5-24 VDC power (30 mA max. load).
Flow sensor connection configuration: RED - 5-26 VDC power (+)
BLACK - POWER (-), COMMON
GREEN - SENSOR NPN OPEN COLLECTOR OUTPUT
“pull-up” resistor is necessary for PLC input with current sourcing. Recommended
value: 2.2 K Ohm for 24 VDC input.
PWM meters supplied with (four wire) RTD options are connected using the stainless
steel temperature sensor adapter supplied.
6. MAINTENANCE
6.1 Sensors
In rare instances, due to electrical damage, the pulse sensor needs to be replaced
by unscrewing it and installing a replacement (hand tight).
The RTD /adapter subassembly is replaceable using a wrench.
6.2 Paddle Wheel Disassembly
Bearings are highly susceptible to careless disassembly and reassembly practices.
The nickel Tungsten Shaft of the Wheel is supported at each end by sapphire bearings
to minimize friction and facilitate very low flow rate measurements.
The Wheel may be uninstalled by holding the Lid in place, and removing the four
mounting screws, very carefully to prevent damaging the sapphire Bearings at each
end of the Shaft. If the Bearings are shattered, they need to be replaced.
Reassembly is made ensuring that the Shaft ends are inserted gently into the sapphire
Bearings. Check to see if the wheel is free to spin before the Lid Bearing is installed.
While holding the Lid in place, blow into the meter to verify that the Wheel is free to
spin. Finally the Lid is reinstalled using the four mounting screws.