Enabling bias resistors on the Honeywell NPB-2X-RS485 option card is a straightforward process that enhances the stability of your RS-485 communication. Bias resistors are critical components that prevent indeterminate idle states on the RS-485 network. To enable these resistors, follow these steps:
- Locate the Jumper Pins: On the component side of the NPB-2X-RS485 option card, identify the bias resistor jumper pins.
- Enable Biasing: Place the two 2-pin jumper blocks (typically included with the card) onto the jumper header associated with the RS-485 port you wish to bias.
- Disable Biasing: To turn off biasing, remove both 2-pin jumper blocks from the port's header.
- Effect of Biasing: When enabled, the bias resistors connect two 3.3K ohm resistors into the RS-485 port circuit, one connecting RS-485 positive to 5V and the other connecting RS-485 negative to Ground.
Remember, bias resistors differ from termination resistors, both of which are important for reliable RS-485 network performance. For detailed instructions and safety precautions, always consult the Honeywell NPB-2X-RS485 option card's manual.