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  • Ethernet Communication Option Boards are Plug & Play field Installable
  • Allows DPM-3 instruments to be polled using Modbus commands
  • Network speeds of 10 or 100 Mbits/sec
  • Can be polled via Ethernet every 2 msec
  • Includes Mini-USB port for programming or data transfer at 38400 baud

LNET1 Ethernet and USB communications board


DPM-3 communications board that plugs into the middle slot of a DPM-3 1/8 DIN digital panel meter. It provides a high-speed Ethernet port to connect the host instrument to a local area network (LAN), plus a USB port for programming or data output to a PC or HMI. High

Ethernet operation complies with IEEE 802.3 and utilizes an industry-standard RJ45 jack for a 10/100 Base-T connection to a local area network (LAN) or directly to a PC or HMI. Data rates can be 10 or 100 Mbits/sec depending on the router. Using Ethernet and Modbus TCP, the DPM-3-OPT-EU board can be polled every 2 msec. Multiple instruments, each with their own assigned IP address, can be individually addressed and polled.

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

Cached operation is a key feature of the DPM-OPT-EU board. It allows the host meter to be polled at the maximum rate allowed by the meter's main board, and in turn to be polled asynchronously at a much faster rate using external Ethernet or USB communications and Modbus RTU/TCP commands. These are documented in our DPM-3 user manual. Updated analog readings can be retrieved every 17 or 20 msec, depending on the meter's 60 Hz or 50 Hz AC line noise rejection setting. Cashed counter readings can be retrieved every 10 msec.

Communications setup uses our free Network Setup (LNS) utility. That software automatically discovers the board's Ethernet IP address assigned by the WiFi router, the COM port used for USB communications, the meter type, and the signal conditioner type. It also allows the IP address to be assigned by the user. The USB port can be used with our free Instrument Setup (IS) software to set up all operating parameters of host instrument and remote instruments on an attached RS485 bus.

Networks with DPM-OPT-EU Boards

Network with DPM-3 Ethernet meters Setup of DPM-3 Ethernet meters


Ethernet Operation

Ethernet application Operation of host meter as a Modbus slave
Ethernet standard IEEE 802.3
Ethernet connector RJ45 jack
Ethernet cable 10/100 Base-T
Data rate 10 or 100 Mbits/sec
Communications protocol Modbus TCP (same commands as for Modbus RTU)
Min read interval from cache 2 msec

USB Operation

USB applications Our Network Setup, host meter programming, operation of host meter as a Modbus slave.
USB connector Mini-USB
USB cable Mini-USB to Type A or customer furnished
Data rate 38400 baud
Communications protocol Modbus RTU (same commands as for Modbus TCP)
Min read interval from cache 10 msec
COM port Discovered by our Network Setup (LNS) utility

Cache Memory

Data written into cache Display value or set of 6 values (user selectable)
6 values for analog in DPM-3’S Alarm status, display value, peak, valley, display value, display value
6 values for scale meters Alarm status, display value, peak, net weight, gross weight, display value
6 values for counters Alarm status, item 1 (display value), peak, valley, item 2, item 3
Write interval for 1 value 18 msec or 21 msec (filtering set for 60 Hz or 50 Hz noise rejection)
Write interval for 6 values 108 msec or 126 msec (filtering set for 60 Hz or 50 Hz noise rejection)
Read inteval from cache Set by externa Modbus Master, 2 msec min for Ethernet, 10 msec min for USB

Measurement Update Intervals

Analog input meter 18 msec or 21 msec (filtering set for 60 Hz or 50 Hz noise rejection)
Totalized pulse readings Signal period or programmable gate time from 10 msec to 199.99 sec
Frequency/rate readings Gate time + 30 msec + 1-2 signal periods

Communication Protocols

Meter polling via Ethernet Modbus TCP (same command set as for Modbus RTU)
Meter polling via USB Modbus RTU (same command set as for Modbus TCP)
Meter programming Custom ASCII protocol for Instrument Setup (IS) software


Board dimensions 79 x 39 mm
Mounting location Middle slot of DPM-3 digital panel meter


Operating temperature -40°C to 85°C
Relative humidity 95% from 0°C to 85°C, non-condensing

Electrical Protection

Isolation 250V rms working, 2.3 kV rms per 1 min test
ESD protection 15 kV per IEC 1000-4-2
EMI immunity 10 V/m per IEC 1000-4-3
EFT protection 2 kV per IEC 1000-4-4
Short circuit protection Continuous
DPM-OPT-EU N/A 188.00