LEFOO LFM31 Series User manual

LFM31 Series Differential pressure gauge
ZHEJIANG LEFOO SENSING TECHNOLOGY CO.,LTD / LEFOO INDUSTRIAL CO., LTD https://en.lefoo.com.cn [email protected]om
01
Features
■Manual button Zero calibration and full scale adjustment
■RS-485 serial communication, support standard ModBus RTU protocol
■Built-in buzzer with sound-light alarm,field programmable
alarm pressure value.
■Housing made of FR-ABS,satisfactory impact resistance and
heat resistance etc.
Description
The LFM31 series is a highly integrated, multi-functional digital, smart transmitter. Adopt mature and
reliable sensor technology. Combined with advanced micro-controller technology and sensor digital
conversion technology designed. LCD display, clear and accurate readings. The core controller adopts
imported single-chip microcomputer, its powerful function and high-speed computing ability ensure the
excellent quality of the transmitter. It can be equipped with on-site segment LCD display. RS-485
network communication can read the current pressure value of the target device in real time. Meanwhile
the LFM31 series has 0~5VDC, 0~10VDC or 4~20mA output modes (individual voltage or current three-
wire output, voltage and current Three-wire output at the same time), Mainly used in the intelligent
building energy management system, to measure the precise pressure and flow required for building
pressurization and air flow control.
Specification
Measurement range
0～±100Pa, 0～±1,000Pa, 0～±10,000Pa
Unit
Pa、KPa、mBar、mmHG、inWC、mmWC,
Accuracy
±1%F.S
Working Temperature
－20℃~70℃
Compensated
Temperature
－10℃~60℃
Protection Grade
IP54
Output Signal
0~5V
0~10V
4~20mA
RS485
Power supply
12~30VDC
Consumption
≤0.75W
Pressure connection
Plastic concave interface
Housing material
UL94-V0/ABS Industrial plastics
Certification
ROHS,CE
Electromagnetic
compatibility
Electromagnetic radiation: EN50081-1/-2; electromagnetic sensitivity:
EN50082-2
Lightning protection
Air conduction withstand voltage 8000V, shell and cable conduction withstand
voltage 4000V (customized)
Display
80*40mm LCD display
Weight
315g

LFM31 Series Differential pressure gauge
ZHEJIANG LEFOO SENSING TECHNOLOGY CO.,LTD / LEFOO INDUSTRIAL CO., LTD https://en.lefoo.com.cn [email protected]om
02
Dimension
Order Ref. NO
Code and description
Notes
LFM31
Mode
6
-100～100pa
Measurement
range
0
-1000~1000Pa
2
-10000~10000Pa
A
4~20mA and 0~5V/0~10V
（Simultaneous output）
E
RS—485
Output mode
B
4~20mA（Three-wire）
F
0~10V and RS—485
C
0~10V（Three-wire）
G
0~5V and RS—485
D
0~5V（Three-wire）
H
4~20mA and RS—485
P
Plastic panel (round)
Installation
panel
S
Stainless steel panel (square)
F
Front panel air intake
Air intake
method
B
Rear panel air intake
LFM31 0 B P B
Model selection
example

LFM31 Series Differential pressure gauge
ZHEJIANG LEFOO SENSING TECHNOLOGY CO.,LTD / LEFOO INDUSTRIAL CO., LTD https://en.lefoo.com.cn [email protected]om
03
Detailed interface
1. Display Function
The pressure value is displayed in the main interface
mode, and the display unit can be switched to Pa, KPa,
mBar, mmHG, inWC, mmWC. (The ±100Pa range
model only has three units of Pa, mmWC and mBar to
choose from)
2. Button operation instructions
3. Menu introduction
(1) Main menu ZERO: (zero function)
When the pressure value is displayed on the main interface, press
the M key to enter the main menu.Press the key to select
ZERO-MENU.Press and hold the key for 2 seconds to enter the
manual zero pressure value.Keep the +/- pressure interface
disconnected in a stable and static environment before performing
zero reset operating. The pressure value should be cleared within
the range of -50～50Pa, otherwise it will fail.
(2) Main menu Unit: (Unit setting)
When the pressure value is displayed on the main interface, press
the M key to enter the main menu. Press the key to select Unit-
MENU. Short press the key to enter the pressure unit setting.
Press the key or key to switch the unit. Press the M key to
save the current unit setting. Press the E key to return to the
previous level menu.
The selectable units are as follows: Pa
KPa mBar
mmHG inWC mmWC
(3) Main menu Filt: (Filter coefficient setting)
When the pressure value is displayed on the main interface, press
the M key to enter the main menu. Press the key to select Filt-
MENU. Short press the key to enter the damping filter coefficient
setting. Press the key or key to switch the filter coefficient.
Press the M key to save the current filter coefficient setting. Press
the E key to return Up the menu.
主界面功能
主菜单功能
子菜单功能
M
1、短按进入主菜
单
2、长按进入关机
3、关机状态下短
按开机
无
确定设置完成按钮

无
向下翻按钮，主菜
单功能选择
数值增加

无
1、短按进入子对
应子菜单设置
2、在ZERO目录下
长按清零设置
1、数值减小
2、移动设置位按钮
E
无
返回主界面
返回上一层主菜单
主界面功能
主菜单功能
子菜单功能
M
1、短按进入主菜
单
2、长按进入关机
3、关机状态下短
按开机
无
确定设置完成按钮

无
向下翻按钮，主菜
单功能选择
数值增加

无
3、短按进入子对
应子菜单设置
4、在ZERO目录下
长按清零设置
3、数值减小
4、移动设置位按钮
E
无
返回主界面
返回上一层主菜单
Main interface
function
Main menu
function
Sub-menu
function
M
1. Short press to
enter the main menu
2. Long press to enter
shutdown
3. Short press to turn
on when it is off
NO
"OK"button

NO
Down button,
main menu
function
selection
Increase in
value

NO
1. Short press
to enter the
corresponding
sub-menu
setting
2. Long press
the reset
setting in the
ZERO
directory
1. Decrease
the value
2. Move the
setting button
E
NO
Back to main
interface
Return to the
previous main
menu

LFM31 Series Differential pressure gauge
ZHEJIANG LEFOO SENSING TECHNOLOGY CO.,LTD / LEFOO INDUSTRIAL CO., LTD https://en.lefoo.com.cn [email protected]om
04
(4) Main menu S-H: ( Alarm upper limit setting)
When the pressure value is displayed on the main interface, press the M key to enter the main menu, press the key to select SH-
MENU. Short press the key to enter the pressure upper limit setting, press the key to select the pressure value. The current digit
LCD flashes. Press the current selection digit value to increase. Press M Key to save the current upper limit pressure value. Press E key
to return to the previous menu. Note: The upper limit of pressure should be greater than the lower limit,it can be set correctly. Otherwise it
will prompt an error and not save.
(5) Main menu S-L: (Alarm lower limit setting)
When the pressure value is displayed on the main interface, press the M key to enter the main menu. Press the key to select SL-
MENU. Short press the key to enter the pressure lower limit setting. Press the key to select the pressure value, the current digit LCD
flashes. Press the key current selection digit value to increase. Press M Key to save the current upper limit pressure value. Press E
key to return to the previous menu. Note: The upper limit of pressure should be greater than the lower limit,it can be set correctly.
Otherwise it will prompt an error and not save.
(6) Main menu bEEP: (Alarm switch setting)
When the pressure value is displayed on the main interface, press the M key to enter the main menu. Press the key to select bEEP-
MENU. Short press the key to enter the alarm switch setting, press the key to select the alarm switch on or off. Press the M key to
save the current alarm Switch status setting. Press E key to return to the previous menu.
(7) Main menu no.: (peak viewing mode)
When the pressure value is displayed on the main interface, press the M key to enter the main menu. Press the key to select no.-
MENU. Short press the key to enter the maximum pressure peak view mode. Press the key or key to select the Min. pressure
value or the Max. pressure value. Press the E key to exit the pressure view Mode, return to the previous menu.
(8) Main menu rSEt: (restore factory settings)
When the pressure value is displayed on the main interface, press the M key to enter the main menu. Press the key to select rSEt-
MENU. Short press the key to enter the password input mode. Press the key password value selection digit, the current digit LCD
flashes. Press the key current selection digit value to increase. Press the M key to save the current Enter the password. The factory
setting password is: 1234. If the input is correct, the factory settings will be restored. If the input is incorrect, the error code Err4 will be
displayed. Press the E key to return to the previous menu.
4. System error flag:
Err1: Clear zero Failed.
Err2: The upper limit setting failed (the upper limit must be greater than the lower limit)
Err3: The lower limit setting failed (the upper limit must be greater than the lower limit)
Err4: The restoring factory settings password is entered incorrectly
Err5: Pressure transmitter error
Wiring definition
The wiring terminal of M31 series pressure transmitter is shown in Figure 1.The terminal definition is shown in
Table 1.
Notes:
1. Make sure that the wiring is correct. If the power cord is connected to the communication terminal by mistake, it will
cause irreversible damage to the communication part!
2. Select the output type according to the M31 transmitter and connect the terminals correctly.If the transmitter type is
voltage output, connect the DC power supply to the power supply interface. Connect the positive pole of the voltmeter
to the "U-OUT" voltage detection terminal and the negative pole to "—" terminal.
3. In order to ensure normal long-distance communication, you can use a shorting cap to insert the "CN2" header,
which has a 120 Ωmatching resistor in parallel.
Terminal NO
Terminal definition
+
+16~30Vdc
Power supply interface
—
GND
I-OUT
Current
Detection
The positive terminal of the
ammeter, the other is
connected“-”端
U-OUT
Voltage
detection
Voltmeter positive, negative
connection“-”
B
B-
RS-485 Communication
Interface
A
A+
CN2
Match
resistance
Use shorting cap for remote
communication

LFM31 Series Differential pressure gauge
ZHEJIANG LEFOO SENSING TECHNOLOGY CO.,LTD / LEFOO INDUSTRIAL CO., LTD https://en.lefoo.com.cn [email protected]om
05
Product use steps
Installation method
Bracket installation Panel installation
主界面功能
主菜单功能
子菜单功能
M
1、短按进入主菜
单
2、长按进入关机
3、关机状态下短
按开机
无
确定设置完成按钮

无
向下翻按钮，主菜
单功能选择
数值增加

无
5、短按进入子对
应子菜单设置
6、在 ZERO 目录
下长按清零设置
5、数值减小
6、移动设置位按钮
E
无
返回主界面
返回上一层主菜单
4. 显
示
功
能
主界面功能
主菜单功能
子菜单功能
The use of the transmitter product is divided into
three stages. Firstly, install and connect correctly;
secondly, power on to display the set value of the
read parameter; finally enter the main interface to
display the pressure change value or output the
analog signal or digital signal.
2. Open a hole on the panel that needs to be mounted. The
hole diameter is 120mm.Insert the product and install the lug
on the back, and then fix it on the panel from the back with
ST3.5x30 screws. The pressure port is reliably connected
with the air duct, and pay attention to the difference between
the high and low pressure ports.
1. First, fix the metal bracket to the wall with self-tapping
screws ST3.5x30. Finally use the self-tapping screws
ST3.5x9 to fix the product to the metal bracket. The
pressure port is reliably connected with the air duct, and
pay attention to the difference between the high and low
pressure ports.
3 Lugs
Wall
Metal bracket
Product
Wall
Product
Input range setting
1. Set the range from the "S-H" output upper limit and "S-L"
output lower limit. Select the "out" output type corresponding to
the transmitter model.
<Example> The output type is set to RS-485 and voltage type
0~10V at the same time; the output upper limit is set to 1000
Pa, and the output lower limit is set to 0 Pa.According to the
RS-485 communication protocol, the real-time output changes
Pressure value.The voltage detection terminal outputs a linear
proportional voltage. If the pressure is 500Pa, the output
voltage is 5V. When the pressure is greater than or equal to
1000Pa, the output voltage value is 10V.As shown in the right
figure.
2. Within the range of the transmitter, the upper limit of "S-H"
output and the lower limit of "S-L" output can be set
arbitrarily.Only the upper limit must be greater than the lower
limit,then it can be set correctly.

LFM31 Series Differential pressure gauge
ZHEJIANG LEFOO SENSING TECHNOLOGY CO.,LTD / LEFOO INDUSTRIAL CO., LTD https://en.lefoo.com.cn [email protected]om
06
Spring embedded installation Spring panel installation
Accessories
Air duct, metal bracket, plastic lug, self-tapping screw, downlight circlip, expansion tube
Common problems and solutions
If the transmitter fails, please refer to the content listed in the troubleshooting table for troubleshooting, as shown in Table 2
M
1、短按进入主菜
单
2、长按进入关机
3、关机状态下短
按开机
无
确定设置完成按钮

无
向下翻按钮，主菜
单功能选择
数值增加

无
7、短按进入子对
应子菜单设置
8、在ZERO目录下
长按清零设置
7、数值减小
8、移动设置位按钮
E
无
返回主界面
返回上一层主菜单
主界面功能
主菜单功能
子菜单功能
M
1、短按进入主菜
单
2、长按进入关机
3、关机状态下短
按开机
无
确定设置完成按钮

无
向下翻按钮，主菜
单功能选择
数值增加

无
9、短按进入子对
应子菜单设置
10、在ZERO目录
下长按清零设置
9、数值减小
10、移动设置位按
钮
E
无
返回主界面
返回上一层主菜单
主界面功能
主菜单功能
子菜单功能
M
1、短按进入主菜
单
2、长按进入关机
3、关机状态下短
按开机
无
确定设置完成按钮

无
向下翻按钮，主菜
单功能选择
数值增加

无
11、短按进入子对
应子菜单设置
12、在ZERO目录
下长按清零设置
11、数值减小
12、移动设置位按
钮
E
无
返回主界面
返回上一层主菜单
主界面功能
主菜单功能
子菜单功能
M
1、短按进入主菜
单
2、长按进入关机
3、关机状态下短
按开机
无
确定设置完成按钮

无
向下翻按钮，主菜
单功能选择
数值增加

无
13、短按进入子对
应子菜单设置
14、在ZERO目录
下长按清零设置
13、数值减小
14、移动设置位按
钮
E
无
返回主界面
返回上一层主菜单
Fault
Cause Analysis
Method of exclusion
The transmitter has no
display or cannot
communicate
Transmitter is not powered
Wiring error
Correctly wire the transmitter according
to the wiring diagram
When the pressure is not
connected, the display is
not 0Pa
Slight deviation due to different
environments such as altitude or
temperature
Clear through the menu setting when no
pressure is connected
Transmitter display or
output does not match the
measured pressure
Incorrect supply voltage
External load is too large
Supply voltage (12V~30V)
Adjust external load
No change in pressure
display or output value after
pressurization
1. The intake pipe is blocked by foreign
matter
2. The medium is corrosive or is
different from the applicable medium of
the purchased product
1. Replace the intake pipe
2. Choose the measuring medium used
Wall
4. Open a hole on the panel , the diameter of the hole
is 120mm. Turn the downlight circlip and press it into
the panel to fix the product on the panel. The pressure
port is reliably connected with the air duct, and pay
attention to the difference between the high and low
pressure ports.
3. Open a hole on the wall. The hole diameter is
120mm. Insert the downlight circlip and this product
into the wall at the same time, so that the downlight
circlip presses the wall to fix it. The pressure port is
reliably connected with the air duct, and pay
attention to the difference between the high and low
pressure ports.
Downlight circlip
Product
Downlight circlip
Product
Wall