S
E
N
S
O
R
S
A
Operation and Wiring
N
D
IN
S
T
R
U
M
E
N
T
A
T
IO
N
F
O
R
M
A
C
H
IN
E
C
O
N
D
IT
IO
N
M
O
N
IT
O
R
IN
G
Standard Wiring
The Model 640/641/645/646 B Series operates from a standard 2-wire, 4-20mA loop. If using a loop powered
unit, attach the positive (+) input from the power supply to Pin A or
Red
wire on the sensor and the negative (-)
input from the power supply to Pin B or
Blue
wire of the sensor.
Figure 1 – wiring: loop powered
Figure 2 – wiring: loop powered/DC source
If using a standard DC power supply, install either an ammeter and/or load resistor in line with the output, Pin B or
Blue
wire.
The resistor will generate a DC voltage that is proportional to current by:
V
IR
=
If R
ohms and I
mA then V
VDC
=
=
=
500
6
3
,
Note:
- Resistor value must be less than: (Vsupply – 12) x 50.
- For integral cable sensors: RED wire is positive, BLUE wire is negative.
PAGE 5
