General Measure GM7702 User manual

GM7702
User Manual
GM7702-00180101
110607040003
VER01.00.12

©2018, Shenzhen General Measure Technology Co., Ltd
This manual is subject to change without notice at any time to improve the product. No
part of this manual can be photocopied, reproduced, or translated into another language
without the prior written consent of the General Measure Company.
Website: http://www.gmweighing.com
Implementation of standards: GB/T 7724—2008

Table of Contents
1 General Description......................................................................... - 1 -
1.1 Functions and Characteristics...............................................- 1 -
1.2 Front Panel Description........................................................- 2 -
1.3 Connector diagram............................................................... - 3 -
1.4 Technical Specifications.......................................................- 4 -
1.4.1 Common:...................................................................- 4 -
1.4.2 Analog:......................................................................- 4 -
1.4.3 Digital:...................................................................... - 4 -
2 Installation and Wiring.................................................................... - 6 -
2.1Connection of Power Supply.................................................- 6 -
2.2 Connection of Load Cell...................................................... - 6 -
2.3 Connection of I/O Terminal..................................................- 8 -
2.4 Serial Port Output...............................................................- 10 -
2.5 Connection of Analog.........................................................- 12 -
3 Data Input and Parameters.............................................................- 15 -
3.1 Parameters List...................................................................- 15 -

3.2 Data Input........................................................................... - 20 -
4. Calibration.................................................................................... - 22 -
4.1 Description......................................................................... - 22 -
4.2 Calibration Parameter.........................................................- 22 -
4.2.1 Empty Scale Calibration......................................... - 23 -
4.2.2 Weight Calibration.................................................. - 24 -
4.2.3 Calibration without Weight..................................... - 25 -
4.3 Calibration Record............................................................. - 26 -
5 Control Parameter..........................................................................- 28 -
6 I/O Module.....................................................................................- 31 -
6.1 I/O Module Define............................................................. - 31 -
6.2 I/O Module Test..................................................................- 32 -
7. Password Management................................................................. - 33 -
8. Serial Port Communication...........................................................- 34 -
8.1 r-Cont Mode...................................................................... - 34 -
8.2 Modbus Protocol................................................................ - 35 -
8.2.1 Modbus Address......................................................- 36 -

8.3 Modbus RTU、Modbus ASCII protocol........................... - 45 -
8.4 Chi mei PT650D Protocol.................................................. - 53 -
9 Dimension......................................................................................- 55 -

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1 General Description
GM7702 weighing indicator is specially designed for weight transmitting in industrial
fields. This indicator has the features of small volume, plenty communicating commands, stable
performance, easy operation and practicability. It can be widely applied to concrete and bitumen
mixing equipment, metallurgy furnace and converter, chemical industry and feed, etc..
1.1 Functions and Characteristics
small volume, unique design and easy operation
applicable to all kinds of resistance strain gauge bridge load cell
front panel numerical calibration
multilevel of digital filter
automatic zero-tracking
automatically zero when power on
serial communication interface: RS232 or RS485
calibration via serial interface (Serial interface sets ON)
support 16-bit resolution DA output
2 In and 3 Out, support limit control output
online upgrade via RS232 serial port
tare weight function

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1.2 Front Panel Description
Status:
ZERO: Light on when material weight is 0±1/4d.
STAB: Light on when material weight is within stable range.
NET: Light on when indicator is in net weight status.
COM: Light on when in communication status.
Keypad:
ZERO/ESC: Used to exit from current operation or go previous page.
In the status of net weight, press this key will enter gross weight status.
TARE: In the status of gross weight, press OPTION will tare and indicator show net
weight value.
When data input, the main display flash and the flash position will move.
MODE：To make flashing position move to the right digit when data inputting.
ENTER: Enter option when calibration or in parameter setting and can be used as

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analog switching display.
1.3 Connector diagram

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1.4 Technical Specifications
1.4.1 Common:
Power supply: DC24V±5%
Working temperature: -10～40℃
Max humidity: 90%R.H without dew
Power consumption: about 0.8W
1.4.2 Analog:
Load cell power: DC5V 100mA（MAX）
Input impedance: 10MΩ
Zero steady range: 0.00~12mV (Load cell 3mV/V)
Input sensitivity: 0.1uV/d
Input range: 0.00～15mV(Load cell 3mV/V)
Transfer mode: Sigma - Delta
A/D conversion speed: 120/240/480 times/sec.
Non-linearity: 0.01% F.S
Gain drift: 10PPM/℃
Display precision: 1/100000
1.4.3 Digital:
Weight display: 128*32 0.91”White light OLED
Minus display: “-”
Overload display: Voltage overlimit/underlimit

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Decimal point: 5types (optional)
Function keys: 4keys soniferous keypad

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2 Installation and Wiring
2.1Connection of Power Supply
GM7702 weighing indicator connects with DC24V power supply as follows, which has
two lines connecting ports. The correct wiring of the power terminal is shown in the figure
below:
2.2 Connection of Load Cell
GM7702 weighing indicator connects with bridge type resistance strain gauge load cells
by 4 wires. (When use 6-wired load cells, you must bridge the EX+ with SN+ and bridge the
EX- with SN-.) It could connect with no more than 4 units load cell of 350Ω .
Each port of the load cell connection terminal is allocated as
Plea ※Please pay attention to the positive and negative polarity of the
power supply, do not connect the reverse

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2.2.1 Load Cell Connection
Note:
4 wires
EX+
EX-
SG+
SG-
SHLD

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1. As load cell output signal is sensitive to electronic noise, the wiring should be shield cable
and separate with other cables, especially AC power.
2．4 wires connection is suitable for short distance and stable temperature or low precision
field, otherwise use 6 wires connection.
3．For more load cells parallel connection, their sensitivity (mV/V) should be the same.
2.3 Connection of I/O Terminal
GM7702 weighing indicator has equipped with I/O module of 2 IN and 3 OUT. IN/OUT
function user can self-define. To facilitate users wiring and some special applications, the
default definition is as follows
O u t p u t
In p u t
O U T 1
s t a b l e
IN 1
z e r o
OU T 2
o v e rl i m i t
IN 2
tare
O U T 3
set point 1

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Indicator input terminal connection:
Indicator output terminal connection:

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2.4 Serial Port Output
GM7702 weighing indicator possesses RS232 and RS485 serial port, which support
Modbus-RTU protocol, r-SP1,r-Cont and Chi mei PT650D protocol.
Communication parameters:
Item
Option
Description
1. serial port RS232
2. serial port RS485
ID No.
initial value: 01; range: 01-99.
baud rate
initial value: 38400; option: 9600, 38400,
57600, 115200.
data format
initial value: 8-E-1; option: 8-E-1, 8-O-1,
8-N-1, 7-E-1, 7-O-1.
communication
Initial value: Modbus-RTU; option:
Modbus-RTU, r-Cont,
Modbus-RTU(2),Modbus-ASCII , PT650D.
Modbus Hi-Lo
initial value: AB CD; option: AB CD(Hi-Lo), CD
AB(Lo-Hi)
sending interval
initial value: No interval; option: no interval,
10msec, 20msec, 50msec.
data sending interval in r-Cont mode
The serial port interface definition diagram is shown on the left
RS485 Connection mode:

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RS232 Connection mode:
9 pin connector
25pin connector
or
computer
Indicator

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2.5 Connection of Analog
There are two types of analog output:
1) Voltage output: 0-5V, 0-10V.
2) Current output: 4-20mA.
3) User-define function: user can define analog output type and output range.
Analog parameter
Item
Option
Description
Working mode
4-20mA
Weight value could be converted to current of
4-20mA.
0-5V
Weight value could be converted to voltage of 0-5V.
0-10V
Weight value could be converted to voltage of 0-10V.
user-defined
current
User can define the current or voltage.
user-defined
voltage
Min. output
value
initial value:
00.000
To set min. analog output value. (The value will not
change if the converted value smaller than set value.)

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Zero output
value
initial value:
00.000
To set analog output value of zero point weight value.
Max. capacity
output value
initial value:
00.000
To set analog output value of max. capacity.
Max. output
value
initial value:
00.000
To set max. analog output value. (It will not change if
converted value bigger than set value.)
Analog output ports defined as below:
V+: Positive voltage output；V-: Negative voltage output
I +: Positive current output；I-: Negative current output

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The indicator has been calibrated on the analog output when it leaves the factory, user no
need to calibrate the analog output. If the analog output is abnormal, user can calibrate the
analog output by himself (it is recommended to calibrate under the guidance of a professional).
Calibration method (use a multimeter to connect the analog interface):
※Select calibration point and press ENTER. Contact to
multimeter and input the display value, finally press
ENTER to complete.
※Analog calibration has 4 steps to complete.
Change option by pressing MODE key.
1. Working parameter
2. Calibration parameter
1. 4mA calibration
2. 12mA calibration
3. 20mA calibration
4. 24mA calibration
※In parameter interface, pressing TARE and ENTER 3s
to enter analog calibration.

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3 Data Input and Parameters
3.1 Parameters List
In the status of weighing, user could enter parameter interface by MODE key, and change
item by TARE or MODE, then press ENTER to edit parameter.
Item
No.
Parameter
Parameter
item
Description
1
Working
parameter
power-up zero
initial value: OFF (option: ON / OFF)
To proceed zero judgment when power on.
zero tracking
range
initial value: 0. (range: 0~9d)
Automatic judgment of zero point if weight
value is within set time and range.
zero tracking
time
initial value: 1.0 (0.0~9.9s)
Automatic judgment of zero point if weight
value is within set time and range.
stable range
initial value: 01. (range: 00~99d)