36 • VOC Pro Transmitter
Modbus Baud Setting
The baud rate is the speed of data transmitted within the Modbus system, measured in bits per
second (bps). For successful communication, the baud rate setting of the VOC Pro MUST
match the baud rate setting on the connected controller or other Modbus device.
The VOC Pro’s default Modbus baud setting is 9600 bps. The RS-485 Modbus
communication parameters used in the VOC Pro are 8 data bits, no parity bit, and 1 stop bit
(8-N-1) these parameters are fixed and cannot be changed. Some devices come with different
Modbus baud rates. Check with your system administrator to determine if a different Modbus
baud setting is needed for your system.
The pre-set Modbus baud setting available for the VOC Pro are the following:
•
110 bps
•
300 bps
•
1200 bps
•
2400 bps
•
4800 bps
•
9600 bps
•
19200 bps
1. If necessary, enter the Product Settings and Configuration menu by pressing and holding
the MENU button for 6 seconds.
2. Press and release the MENU button until the Modbus Baud screen appears.
3. Use the ADD and SUB buttons to scroll through the available Modbus baud options.
4. Press and release the MENU button to move through the Product Settings and
Configuration menu or to exit to the normal operating mode screen.
4-20 mA Offset Settings
Setting the 4-20 mA offset allows the end-user to calibrate the sensor’s analog output. Upon
installation of the device, if the detected gas reading on VOC Pro does not correspond to the
reading on the controller, the zero offset (4 mA) and the full-scale offset (20 mA) can be
adjusted on the unit.
Over time, as electronic components suffer from normal wear and tear, the circuits will tend to
drift. This drift can cause variances in the amount of current output by the sensor, or in the
current measurement by the controller. If at any time the reading on the VOC Pro no longer
matches the reading on the controller, the 4-20 mA offset will need to be recalibrated.