Ideas in Measuring ..
TECHNIQUES LIMITED
Page 4
LDU68 Series Manual
The command set for the LDU XX.X series is based on a simple ASCII format. This consists of a 2
capital letter code which enables the user to setup the device, get results or check parameters.
Example:
An LDU XX.X with the address or channel number 1 is connected via the RS485 port to a bus
system. You want to get the net weight from this device.
In this manual a space is represented by “_” and Enter (CR/LF) by “
¿
”
The command OP_2 opens the communication channel to device #2 and closes communication
with device #1. Now device #2 acknowledges that it is active (OK) and responds to any commands
on the bus. Communication with device #2 will be closed by another OP command (for another
device on the bus e.g. OP_5) or by the close command e.g. CL_2.
Each OP_X command implies a CL command to all other devices on the bus except #X. This makes
the address structure easier and improves system performance.
2 COMMUNICATIONS & GETTING STARTED
2.1 Serial Interface
Communication with the LDU xx.x series is via the RS422/RS485 port. The data format is the
familiar 8/N/1 structure (8 data bits, no parity, 1 stop bit). The LDU xx.x can communicate at the
following baud rates: 9600, 19200, 38400, 57600, 115200 baud.
RS422
!
Connection using a 4 wire technique.
!
Point to Point connection
RS485
!
Connection using 2 or 4 wire techniques
!
Multi-drop connection possible with up to 32 LDU XX.X on a bus.
!
Half duplex only (DX=0).
(RS232)
!
An optional adaptor board model UA77.1 is available, which has a built-in RS422 to RS232
converter
2.2 Command Language
Master (PC / PLC) sends
Slave (LDU XX.X) responds
Status
OP_1
¿
GN
¿
OK
N+123.45
Device number 1 ready
Open Device number 1
Net weight value with sign & decimal point
Get Net weight value
Issue 1h
Page 5
LDU 68 Series Manual
Ideas in Measuring ..
TECHNIQUES LIMITED
2.3 Setup Baud rate / Device Address
The factory default baud rate is 9600 baud. The factory default device address is 0. Under normal
circumstances the baud rate can be changed or viewed using the BR command (Page 30). Similarly,
the device address can be changed or viewed using the AD command (Page 30). If however you do
not know the device baud rate or address, the LDU can be put into a special configuration mode
which allows the baud rate and device address to be reset. On the under side of the LDU PCB are a
set of special solder pads (SW3) - See diagram on page 6. If these solder pads are bridged (shorted
together) then the LDU will enter the special configuration mode on power up.
Baud Rate (In Configuration Mode)
With SW3 pads bridged, the LDU XX.X will enter a special baud rate search mode on power up.
This involves the LDU waiting for a space character (0x20) to be received. The time duration of this
character is measured by the LDU and its baud rate will be set accordingly - i.e. the baud rate of the
terminal sending the space character will be used by the LDU. The factory default baud rate is 9600
baud.
Address Settings (In Configuration Mode)
2.4 Display Mode
With SW3 pads bridged, the LDU XX.X will enter a special configuration mode on power up. It is
possible to set the network address of the device using the AD command. (Address range between
0 and 255). Setting the address to 0 will set it into continuously active mode, where the device will
listen and respond to any command on the bus without the need for an OP xxx command. Factory
default: Address 0
2.5 Getting Started
You will require a:
!
PC or PLC with either a RS422 or RS485 communication port
!
If you are using a PC or PLC with an RS232 port, you will require a RS422 to RS232 converter
(optional unit adaptor UA77.1)
!
Interconnecting cabling - See the wiring diagram on Page 6
!
A load cell / scale with test weights or a load cell simulator
!
A 12-24 V DC power supply capable of delivering approx. 100mA for each LDU and load cell
!
One or more LDU 68.1/68.2
!
The DOP 4 software*
Refer to the wiring diagram on Page 6
*The DOP 4 software with graphical user interface and oscilloscope function is now available for
Windows PCs. Download the latest version of the DOP 4 software from
http://www.haubac.com/haubac.asp?p1=167 together with Quick Start and Users Manuals
In addition to the standard filters, a filter factor (FF) has been added specifically for when the LDU
68 series is used with an external display. The Filter Factor allows a rolling average to be set up
which gives a more stable result on an external display The Get Filtered value (GF) and Send
Filtered value (SF) commands can be used to get or auto-transmit the filtered values for an external
display.
Issue 1h
