1 Weighing module Operating principle
Electrical resistance of metal material changes in proportion to the forces being applied to deform it. The strain gauge measures the deformation as a change in electrical resistance, which is a measure of the strain and hence the applied forces (load).
2 Introduction
- WECON LX3V-2WT expansion module’s resolution is 24-bit. The module can be used for reading signals from 4- or 6- wire configuration;
- Please read through the manual before powering on the module.
- This manual is only applicable for model number: LX3V-2WT. Please double check the mark on your module.
- Using FROM/TO command to read/write data on PLC LX3X.
2.1 Specification
| Item | Description |
| Channel | Double channels |
| A/D converter | 24 bit Δˉ∑ A/D |
| Resolution | 24bit (signed) |
| Speed | 7.5/10/25/50/60/150/300Hz available |
| Polarity | Unipolar and bipolar |
| Non-linearity | ≤0.01% full scale(25oC) |
| Zero drift | ≤0.2μV/ oC |
| Gain drift | ≤10ppm/ oC |
| Excitation Voltage/ load | 5V, load impedance≥200Ω |
| Sensor sensitivity | 1mV/V-15mV/V |
| Isolation | Transformer (power supply) and the optical coupler (signal) |
| Lamp | Power supply lamp, communication lamp |
| Power supply | 24V±20% 2VA |
| Operating temperature | 0~60 oC |
| Storage temperature | -20~80 oC |
| Dimension | 90(L)x58(W)x80(H) mm |
2.2 Valid bits
Refer to sampling frequency in Section 5.2, Chapter 5 of this manual.
3 Dimensions
① Extension cable and connector
② LED COMM: Lit when communicating
③ Power LED: Lit when power present
④ State LED: Lit when normal
⑤ Module number
⑥ Analog signal output terminal
⑦ Extension module interface
⑧ DIN rail mounting slot
⑨ DIN rail hook
⑩ Mounting holes (φ4.5)
- Use the crimp terminals that meet the dimensional requirements showed in the left figure.
- Apply 0.5 to 0.8 N.m (5 to 8 kgf.cm) torque to tighten the terminals against disoperation.
| Terminals | Instruction | Terminals | Instruction |
| 24V+ | Power supply+ | 24V- | Power supply- |
| GND | Grounding | FG1 | CH1 sensor grounding |
| E1+ | CH1 power supply+ (5V) for sensor | E1- | CH1 power supply- (5V) for sensor |
| S1+ | CH1 signal output+ of sensor | S1- | CH1 signal output- of sensor |
| F1+ | CH1 feedback+ of sensor | F1- | CH1 feedback- of sensor |
| E2+ | CH2 power supply+ (5V) for sensor | E2- | CH2 power supply- (5V) for sensor |
| S2+ | CH2 signal output+ of sensor | S2- | CH2 signal output- of sensor |
| F2+ | CH2 feedback+ of sensor | F2- | CH2 feedback- of sensor |
| FG2 | CH2 sensor grounding |
4 Wiring
✎Note:
- Impedance of the weighing sensor is greater than 50 Ω.
- Sensors with 4 wires need to have E1+ and F1+ connected, E1- and F1- connected.
5 BFM instruction
5.1 BFM list
| BFM | Latched | Read/ Write | Function | Default | Range | Description | |
| 0 | O | R | Model | 5012 | LX3V-2WT model number | ||
| 1 | O | R | System version | 15004 | Software & hardware version | ||
| 2 | 42 | O | R/W | Unipolar/ Bipolar | 0 | 0-1 | 0: bipolar 5: 150 Hz; 6: 300 Hz; 7: 600 Hz; 8: 960 Hz; 9: 2400 Hz; 1: unipolar |
| 3 | 43 | O | R/W | Frequency | 1 | 0-9 | 0: 7.55 Hz; 1: 10 HZ; 2: 25 Hz; 3: 50 Hz; 4: 60 Hz; |
| 4 | 44 | X | R | State | 0 | b0: CH1 no-load; b1: CH2 no-load; b2: CH1 overload; b3: CH2 overload; b4: CH1 measured value is stable; b5: CH2 measured value is stable; b6-b15: Reserved; BFM 44: Reserved; | |
| 5 | 45 | X | R | Error Code | 0 | It is the data register for all error states, and each error status is displayed in the corresponding bit, possibly with multiple error states 0: No error; 1: Error; b0: Power supply error; b1: Hardware error; b2: CH1 conversion error; b3: CH2 conversion error; B4 :CH1 input calibration parameter error Other bit: Reserved; BFM45: Reserved; | |
| 6 | 46 | X | R/W | Tare weight Preset | 0 | 0-1 | Use average weight as tare weight: 0: Disabled 1: Set tare weight then reset to 0; Others : Reserved; |
| 7 | 47 | O | R/W | Gross/Net weight | 0 | Display gross weight or net weight 0: Gross weight; 1: Net weight; Others: Channels invalid; | |
| 8 | 48 | X | R/W | Weight Calibration | 0 | Defaulted to 0 0x0001:Channels 1 set to 0 0x0002:Channels 1 calibrating: 0x0003:CH1 without weight calibration parameter error Step1: Remove all load ; Step2: BFM #8 (#48) set to 0x0001; Step3: Add known weight; Step4: Write known weight to BFM#23 (#63); Step5: BFM #8 (#48) set to 0x0002;Calibration without weight: Step1: Do not put any weight on the load cell; Step2: Write the maximum range of the sensor to #23; Step3: Write the sensor sensitivity to #39, accurate to three decimal places; Step4: The value of #8 is written as 0x0003. Modify calibration parameters: Step1: Modify the calibration parameter values in BFM#35~BFM#38; Step2: The value of #8 is written as 0x0004. Remark: After writing the value to BFM#8 using the device monitoring, it will be automatically reset to 0. | |
| 9 | 49 | X | R/W | Reset to default | 0 | 0-3 | #49: Keep unused 1: Reset CH1; 2: Reset CH2 3: Reset all channels Other: No action |
| 10 | 50 | O | R/W | Filtering mode | 0 | 0-1 | Recalibration required after change |
| 11 | 51 | O | R/W | Filtering strength | 3 | 0-7 | Recalibration required after change |
| 12 | 52 | O | R/W | No Load Zero tracking intensity | 0 | 0-200 | 0: Zero tracking disabled Other: Intensity of zero tracking |
| 13 | 53 | O | R/W | No Load Zero tracking range | 0 | 1-300 | 0: No limit Others: Up limit |
| 14 | 54 | O | R/W | No load Zeroing at startup | 0 | 0-4 | 0: Disabled; 1: ±2%MAX; 2: ±5%MAX; 3: ±10%MAX; 4: ±20%MAX; |
| 15 | 55 | X | R | Sensor sensitivity setting | 4 | 0-5 | 0: < 1V/V 1: < 125mV/V 2: < 62.5mV/V 3: < 31.25V/V 4: < 15.625mV/V 5: <7.812 mV/V Note: Please recalibrate after setting (This function only is available in Software & hardware version 13904 or later) |
| 16 | 56 | X | R | Average weight L | 0 | Signed 32-bit integer | Average weight (Low word) |
| 17 | 57 | Average weight H | Average weight (High word) | ||||
| 18 | 58 | O | R/W | Sliding average | 5 | 1-50 | Setting range: K1~K50; settings outside of this range will be changed to the nearest value in the range. |
| 19 | 59 | O | R/W | Tare weight L | 0 | -2147483648~ 2147483647 | User can write or read tare weight by command #7 |
| 20 | 60 | Tare weight H | |||||
| 21 | 61 | O | R/W | CH1 stability check time | 200 | 0-20000 | Stability inspection time, used in conjunction with the stability inspection range, unit: ms |
| 22 | 62 | O | R/W | Stability inspection range | 1 | 1-100 | If the stability check range is set to 100 and the stability check time is set to 200ms, then the current weight fluctuation range is within 100 and lasts for 200ms, then the value is considered stable, otherwise it is considered unstable, and the stability flag is displayed on BFM#4 |
| 23 | 63 | O | R/W | Weight value adjustment L | 1000 | -2147483648~ 2147483647 | Please refer to #8 With weight calibration, enter the weight base point weight, without weight calibration enter the sensor range |
| 24 | 64 | Weight value adjustment H | |||||
| 25 | 65 | O | R/W | Maximum L | 32767 | -2147483648~ 2147483647 | User can set the max value, it will record the error code when measured value exceed set value |
| 26 | 66 | Maximum H | |||||
| 27 | 67 | O | R/W | Zero weight detection up limit | 10 | -2147483648~ 2147483647 | Zero weight detection function, used to tell if all loads have been removed. Reading of the bit to indicate stable reading becoming 0 means all loads have been removed. |
| 28 | 68 | ||||||
| 29 | 69 | O | R/W | Zero weight detection down limit | -10 | -2147483648~ 2147483647 | |
| 30 | 70 | ||||||
| 31 | 71 | X | R/W | Additional function options | 0 | 0~1 | 0: Default, disable additional functions; 1: Enable filter reset function. Other: Reserved |
| 32 | 72 | X | R/W | Additional function parameters | 0 | 0~100 | Enable filter reset function: 0: Default; 0~100: The number of sampling cycles to wait for the filter to restart. The value collected during the accumulation of the average, as the initial value of filtering |
| 33 | 73 | X | R | Digital value L | 0 | - | The number of ADC acquisitions |
| 34 | 74 | X | R | Digital value H | |||
| 35 | 75 | O | R/W | Calibration parameter A | 1 | -3.402823E+38~ 3.402823E+38 | Explain by CH1: After modifying the calibration parameters, #8 does not write 4, which is only displayed, not used for weight value calculation, and does not save after power off; #8 After writing 4, if the parameter range is correct, write and save it for weight value calculation 4 Error code Bit4 is set to 0, if the parameter range is wrong, no write operation will be performed, #4 error code Bit4 is set to 1. |
| 36 | 76 | ||||||
| 37 | 77 | O | R/W | Calibration parameter B | 0 | -3.402823E+38~ 3.402823E+38 | |
| 38 | 78 | ||||||
| 39 | 79 | O | R/W | Sensor sensitivity (specification) | 2000 | 0-32767 | The default setting of 2000 represents 2mV/V, and calibration without weights needs to set the sensor sensitivity accuracy. The sensitivity range can be set to 0~32.767mV/V, the sensor sensitivity BFM#39 enters a negative value, and it is directly converted to 32767 for execution. Example: Modified to 1942 means 1.942mV/V. |
| 40 | 80 | O | R/W | Sensor feedback voltage L | 0 | - | Write: 0: do not display 1: Real-time display of current sensor feedback voltage 2: Display the zero point voltage during calibration 3: Display the voltage of the weight applied during calibration Read: Display the low digit of the voltage value in uV. |
| 41 | 81 | O | R | Sensor feedback voltage H | 0 | - | Read: Display the high digit of the voltage value in uV. |
✎Note:
- O: yes;
- X: no;
- R: read;
- W: write;
5.2 Buffer (BFM) description
- BFM0: Module code
LX3V-2WT V3 code: 5012
- BFM1: module version
Module version (decimal)
Example
BFM1=120, means V1.2.0
- BFM2: Polarity
For bipolar, the signal will go through zero while it is in changing process, but unipolar will not. The result of the conversion from analog value to digital value is signed, so for bipolar signal the value could be minus.
- BFM3: Sampling frequency
The frequency of input signal reading, the lower the frequency is, the more stable the value it gets, and the higher the precision is, but the lower speed gets.
| Setting | Sample frequency (HZ) | Sample precision (Bits) | Setting | Sample frequency (HZ) | Sample precision (Bits) |
| 0 | 7.5 | 23.5 | 5 | 150 | 21.5 |
| 1 | 10 | 23.5 | 6 | 300 | 21 |
| 2 | 25 | 23 | 7 | 600 | 20.5 |
| 3 | 50 | 22 | 8 | 960 | 20 |
| 4 | 60 | 22 | 9 | 2400 | 17.5 |
- BFM4: State code
| Bit No. | Description | |
| 1 | 0 | |
| Bit 0 | CH1 no-load | CH1 load |
| Bit 2 | CH1 over-load | CH1 not over-load |
| Bit 4 | CH1 stable | CH1 unstable |
| Bit 6 | CH1 uncalibrated/calibrated error | CH1 calibration successful |
Bit 8 Bit 9 | 00: no error 10: The base point of the weight is too heavy | 01: No-load calibration 11: Not calibrated |
| Bit 12 | CH1 exceeds the sensor range Note: Determined by sensor feedback voltage | CH1 within the sensor range |
- BFM5: Error code
| Bit No. | Value | Error | Bit No. | Value | Error | |
| bit 0 | K1(H0001) | Power failure | bit 1 | K1(H0001) | Hardware failure | |
| bit 2 | K4(H0004) | CH1 conversion error | bit 3 | K8(H0008) | CH2 conversion error | |
| bit 4 | K16(H0010) | CH1 write calibration parameter error | bit 5 | K32(H0020) | CH2 write calibration parameter error | |
| Other | Reserved | BFM#45 | Reserved | |||
| ✎Note: The data register that stores all error states. Each error state is determined by a corresponding bit. More than two error states may occur at the same time. 0 means normal and no error, and 1 means there is a state. | ||||||
- BFM6: Tare weight setting
Set the current weight value (BFM16-17) as a tare (BFM19-20) weight. Every bit represents a different channel, which is set to 1 to mean enabled, reset to 0 after being set.
Use CH1 as example
The current weight is 100, after setting tare weight;
If it displays gross weight (BFM7 = 0) currently, the tare weight (BFM19-20) will become 100, the current weight is still 100;
If it displays net weight (BFM7 = 1), the tare weight (BFM19-20) will be original value + current weight value, the current weight value becomes zero;
- BFM8: Adjust the weight command. User adjustment steps: (describe with CH1)
There is a weight calibration:
Step1: Do not put any weight on the load cell;
Step2: #8 value is written as 0x0001;
Step3: Add standard weights to the load cell;
Step4: Write the weight of the current weight on the chassis to #23;
Step5: The #8 value is written as 0x0002.
Calibration without weight:
Step1: Do not put any weight on the load cell;
Step2: Write the maximum range of the sensor to #23;
Step3: Write the sensor sensitivity to #39, accurate to three decimal places;
Step4: The #8 value is written as 0x0003.
Modify calibration parameters:
Step1: Modify the calibration parameter values in BFM#35~BFM#38;
Step2: The #8 value is written as 0x0004.
Remarks: After using the device monitoring to write a value to BFM#8 or BFM#48, it will automatically reset to 0.
- BFM11: filtering strength
The higher the filter strength is, the more stable and accurate the weight value is. But the delay time will increase accordingly, and the sensitivity will decrease.
- BFM12: zero tracking strength
Zero-tracking is to have a constant 0 when there’s no load. Zero tracking intensity means the weight counts 0 when it’s within the range to reduce the influence of temperature drift.
| Setting | Description | Note |
| 0 | Zero tracking OFF | Default |
| 1-200 | Range of weight value | 10 means ± 10 |
| Others | Reserved | |
| ✎Note: This feature can be disabled when high precision is not required. | ||
- BFM13:Range of Zero tracking
Accumulated range of zero tracking, stop tracking when out of range
Table 5‑6
| Setting | Description | Note |
| 0 | Disable zero tracking | Default |
| 1-300 | Range of weight value | 10 means ±10 |
| Others | Reserved | |
| ✎Note: This feature can be disabled when high precision is not required. | ||
Example
Setting value is 100, when the position within ± 100, it will be read as no-load.
- BFM15: Set AD chip gain
It can be set according to the sensor range
| BFM15 | Voltage range | Sensor sensitivity |
| 0 | ± 5V | < 1V/V |
| 1 | ± 625mV | < 125mV/V |
| 2 | ±312.5 mV | < 62.5mV/V |
| 3 | ±156.2 mV | < 31.25V/V |
| 4 | ±78.125 mV | < 15.625mV/V |
| 5 | ±39.06 mV | <7.812 mV/V |
5.3 Function Instructions
Net weight measurement
It can be set to measure net weight or gross weight. The Net weight means the weight of the product itself, that is, the actual weight of the product without its external packaging.
The weight of the packaging is called the tare weight. The gross weight is the total weight, namely the net weight plus the tare weight.
- Tare weight: weight of the packaging
- Net weight: the weight of the product, excluding the packaging.
- Gross weight: the net weight plus the tare of the product.
- Gross weight= net weight + tare weight.
Example 1
A product weighs 10kg and the carton contains it weighs 0.2kg, then its gross weight is 10.2 kg (net weight=10kg, tare weight=0.2kg, gross weight=10.2kg)
Example2
Use the measured value at CH1 as the net weight. If you know the weight of the packaging already, you can skip the step of reading tare weight.
- Read the tare weight
Step 1: Write H0000 into BFM7.
Step 2: Place the packaging on the CH1 load cell.
Step 3: Write H0001 into BFM6 to take the weight of the packaging as the tare weight.
- Set BFM7 = H00F1.
Standstill check function
When an object is placed on the load cell to measure its weight, you can use the standstill check function to know whether the current reading has been stabilized.
- If the measured value shifts within the range (BFM 22) of standstill check set up by the user, BFM4’bit 4 will be set to “1”.
- If the measured value shifts beyond the range for standstill check set up by the user, bit4 will be set to “0”. They will be set to “1” again when the range is returned to the set range.
Example
The measuring time is 10ms, the times of standstill check is 10, and the range for standstill check is 1,000. When the range for standstill check exceeds 1,000, the reading is considered unstable, i.e. BFM4’bit4 will be set to 0. When the measuring time is within 100ms (10 × 10ms) and the range returns to be within 1,000, BFM4’bit4 will be set to 1 again. We recommend you check if the measured value is stable enough before operating it.
- Zero detection function
Users can use this function to know whether the object has been removed from the load cell. If the BFM4’bit4 is 1, and the BFM4’bit0 and bit1 are 1 as well, the object has been removed from the load cell already, and you can proceed to the next step.
- Filtering
This setting is used to exclude noises from the readings, which are introduced by environmental factors.
6 Example
- Current state of weight
Read the current state BFM4. More information, please refer to 5.2
- Get current weight value
Write average weight value (BFM16) to D0
- Calibrating weight
Step 1: Remove all weights;
Step 2: Write 0x0001 to #8;
Step 3: Add known weights;
Step 4: Write known weights (D2) to #23;
Step 5: Write 0x0002 to #8
*In the new version, the step 1 can be used for manual reset.
Adjustment and calibration are to make sure the weight values of module and the heavy load units of module to be consistent.
- Tare weight and gross weight
Set value as tare weight by writing K1 to BFM6
Set the value as Net weight by writing K1 to BFM7
Set the value as gross weight by writing K0 to BFM7
- Filter method and strength
Set filtering by writing value to BFM10
Set filtering by writing value to BFM11
After setting the filtering mode and filtering strength, need to calibrate again.
- Zero tracking
Zero tracking is used to reduce the temperature drift interference;
Set Zero Tracking Intensity to 0 to disable tracking. Set Zero Tracking Range to 0 to make it is unlimited.
- Calibration without weights
Calibration without weights is performed by the zero point of the sensor and the maximum range of the sensor. The accuracy is related to the sensor specifications and depends on the sensor sensitivity (mV/V).
Example: The sensitivity of LAB-B-B sensor is 2.0±10%mV/V, and there may be a maximum error of 10%, so it is best to use a sensor with a small sensor sensitivity error to use this function.
Step1: Write the sensor range in D8 to BFM23:
Example: measuring range 3kg, D8 value setting 3000
Step2: write the sensor sensitivity in D9 into BFM39:
Example: Sensitivity: 1.942mV/V, D9 value set to 1942;
Step3: write value K4 to BFM8 and confirm to write calibration parameters.
- Modify calibration parameters
Step1: Write the floating point number in D10 into BFM35~BFM36;
Step2: Write the floating point number in D11 into BFM37~BFM38;
Step3: Write value K4 to BFM8 and confirm to write calibration parameters.
✎Note: BFM35, BFM36, BFM37, and BFM38 are real number types (float). Real numbers need to be input when inputting. If the input exceeds the range, BFM5 will report an error in writing calibration parameters.
7 Diagnosis
7.1 Check
- Make sure all cables are connected properly;
- Make sure all rules regarding LX3V expansion modules are met. Such as expansion modules other than digital inputs and outputs are no more than 8 in total. The total number of digital inputs and outputs are no greater than 256.
- Make sure to select the correct operating range in application;
- Make sure power supply is working properly;
- LX3V CPU unit is in RUN mode;
7.2 Check the error
- If the special function module LX3V-2WT V3 does not operate normally, please check the following items.
Check the status of the LINK indicator
Flashing: The extension cable is connected correctly
Otherwise: Check the connection of the extension cable.
- Check the status of the "24V" LED indicator (upper right corner of LX3V-2WT V3)
Lit: LX3V-2WT V3 is normal, and the 24VDC power supply is normal.
Otherwise: the 24V DC power supply may be faulty. If the power supply is normal, it is LX3V-2WT V3 fault.
- Check the status of the "COM" LED indicator (upper right corner of LX3V-2WT V3)
Flashing: Value conversion is operating normally.
Otherwise: check buffer memory #5 (error status).
If any bit (b0, b1, b2) is ON, that is why the COM indicator is off. Detailed description
Please refer to "(6) BFM5: Error Code" in "5.2 Buffer Register (BFM) Description" in "Chapter 5" of this manual.
- Check the sensor and measure whether the voltage between S+ and S- is less than (5*sensor sensitivity) mv. The sensitivity of the sensor can be found on the sensor manual, and the unit is (mv/v). If the voltage at this point exceeds the range, it means the sensor Deformation or wiring error occurred. Measure whether the voltage between F+ and F- is 5V. If it is not 5V, check the sensor wiring.