WM281/291 User’s Manual
Michell Instruments
5
INstallatIoN
2.5
Connections
2.5.1 Electrical Connection
Applicable for the following products:
WM281/291
Pin
1
Power
2
Power supply -
3
RS485 system 0v
4
ground
5
Output Channel 1 Tempe
6
Output Channel 1 Temperature -
7
Output Channel 2 RH +
8
Output Channel 2 RH -
9
RS485 Data +
10 RS485 Data -
13 Output Channel 3 Calc
14 Output Channel 3 Calculated -
Do not connect Pin 2 (V-) to
Pin 4 (Ground)
15 - 27 V AC and 18 - 38 V DC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Figure 3
Electrical Connections
The electrical connection box is located in the main body of the WM281/291 Transmitters.
Undo the four screws on the face of the transmitter and carefully lift up the top panel.
The connector is located on the circuit board.
2.5.2 Earth Connection
A suitable shielded conductor cable with a diameter between 5 and 10mm should be
used for entry and exiting the transmitter housing via the 2 x Pg11 metal glands.
The shielded cable must be suitably grounded to ensure electromagnetic protection.
2.5.3 Power Supply
The power supply required to power the system is:
•
18 V to 38 V DC
•
15 to 27 V AC
The DC and AC power supply enter via the same pcb connection pins.
