B&B Electronics MAP450D installation manual Set Jumper for 3-Wire RS-422/485

The cable shield must not be used as the signal ground.

It is tempting to try and reduce the cost of 5-wire cabling by using a 4-wire cable with the shield used as the signal ground. DON’T DO IT. The initial cost savings are always exceeded by the maintenance costs once the system is operating under field conditions. It is often necessary to completely replace the network com-link with the proper cable (5-wire plus shield) to eliminate noise problems in the system.

The signal ground must not be connected to the chassis or earth ground. The chassis or earth ground is intended as a safety ground for power supplies, EMI filters, voltage spike protection circuits, 120 VAC neutral returns, and all manner of AC and DC driven devices. As a result, the chassis or earth ground can carry large voltage potentials and currents. Connecting the signal ground to chassis or earth ground can damage the devices connected to the com-link.

2.4. Set Jumper for 3-Wire RS-422/485

This step is required only if the OIT will be communicating with the host controller using RS-485 half-duplex 3-wire communication.

JP4A

(Display)

B

Figure 7 MAP450D Jumper Installation

STEPS

1.Remove the protective cover from the rear of the unit.

CAUTION: When the rear cover is removed, the circuitry inside is exposed to possible damage by electrostatic discharge. Refer to Static Awareness on page 4.

2.Locate jumper “JP4” using Figure 7 as a guide. The jumper is installed on the upper two pins of a 3-pin header. This is called Position “A”.

3.Move the jumper to the lower two pins of the 3-pin header (Position “B”). Ensure that the jumper is pressed fully into place.

4.Replace the rear cover and the four retaining screws.

1010-0046A, REV 00