Description

The DPM-3 WiFi, USB and RS485 communication board allows a DPM-3 1/8 DIN digital panel meter, counter or timer to be interfaced to an external PC or HMI via WiFi, USB or RS485. The use of WiFi, which is standard with most computers, avoids the need for communication cables.

WiFi operation complies with the IEEE 802.11 b/g/n wireless standard for data rates up to 72.2 Mbits/sec. The board can be polled every 10 msec using Modbus TCP commands as document in our Communications Boards user manual. Analog readings retrieved via WiFi can be updated 50 or 60 times per second, depending on the meter's 50 Hz or 60 Hz AC line noise rejection setting.

Cached operation is a key feature of the DPM-OPT-WURS485 board. That board polls its host meter at the maximum rate allowed by the meter's main board, such as 60 analog readings per second, and it can in turn be polled asynchronously as a Modbus slave at a much faster rate using WiFi, USB or RS485.

An on-board 2.4 GHz antenna simplifies meter installation, but requires that the meter be installed on a benchtop or in a plastic case that is transparent to radio waves. The on-board antenna has about 10 dB less gain than the external antenna that comes with the DPM-OPT-WUXRS485 board.

A mini-USB connector is standard and can be used for meter programming or for data polling as a Modbus slave at 38400 baud in parallel with polling via WiFi. To connect to the USB port of a PC, use our cable CBL07 or another readily available A-male to Mini-B USB cable.

An RJ11 connector is standard for RS485 and can be used for data polling as a Modbus slave at up to 115200 baud or for operation as a Modbus master at 19200 baud to an RS485 bus with up to 31 adressable DPM-3 meters or SST series transmitters. Meters on the RS485 bus can be daisy chained using our CBL03 data cables. SST transmitters can be added using our BKBD breakout board.

Setup of WiFi, USB and RS485 communications uses our free Network Setup (LNS) utility. That software allows users to enter the WiFi system's SSID and password, which is then, be stored in the WiFi board. It automatically discovers the board's IP address assigned by the WiFi router, the COM port used for USB communications, the meter type, and the signal conditioner type. DPM-OPT-WURS485 board setup and available Modbus commands are documented in our Communications Boards user manual. The USB or RS485 ports can also be used with our free Instrument Setup (IS) software to set up the host instrument and remote instruments on an attached RS485 bus

Basic WiFi Meter Operation

WiFi Meter Operation as an RS485 Gateway