Load Cell (HX711) Symbol
Definition: The Load Cell (HX711) symbol represents a strain-gauge transducer paired with an HX711 24-bit analogue-to-digital converter, used in circuit diagrams to indicate a sensor that converts mechanical force or weight into a digital signal readable by a microcontroller.
Also known as: weight sensor, strain gauge amplifier, HX711 module, force sensor, scale sensor.
What the Load Cell (HX711) symbol means
The Load Cell (HX711) symbol denotes a two-part sensing system: a mechanical load cell (a metal element fitted with strain gauges whose resistance changes under deformation) and an HX711 amplifier/ADC IC that conditions and digitises the millivolt-level differential signal. Together they form a complete weight-measurement front end.
In schematic diagrams the symbol acts as a functional block representing the sensor-plus-converter subsystem. It communicates with a host microcontroller such as an Arduino via a two-wire serial interface (CLK and DAT), delivering 24-bit readings that correspond directly to applied force or mass.
How to identify the Load Cell (HX711) symbol
The symbol is drawn as a rectangular block labelled 'Load Cell / HX711'. Three pins emerge from the block: VCC (supply voltage, typically 3.3 V or 5 V) at the top, CLK (serial clock input from the MCU) and DAT (serial data output to the MCU) on the right side. Some renderings show the load cell element (a beam shape) feeding into the HX711 block to emphasise the two-stage nature of the subsystem.
Function in a circuit
The load cell converts applied mechanical load into a small differential voltage (typically 1–3 mV per volt of excitation at full scale) via four strain gauges arranged in a Wheatstone bridge. The HX711 IC amplifies this signal by a programmable gain of 32, 64, or 128, then digitises it at 10 or 80 samples per second, outputting the result serially on the DAT line clocked by CLK, allowing a microcontroller to read weight values with milligram-level resolution.
Standards: IEC vs ANSI
| IEC 60617 | Load cells are characterised under IEC 60747 (semiconductor devices) for the ADC portion and OIML R 60 for the mechanical load-cell metrology; no single IEC 60617 glyph exists for this composite module. |
|---|---|
| ANSI/IEEE 315 | No dedicated ANSI Y32.2 / IEEE 315 symbol is defined for this module; it is represented as a general functional block per IEEE 315-1975 block-diagram conventions. |
| Key difference | Both IEC and ANSI treat the HX711 load-cell assembly as a functional block; the glyph shape is defined by the tool/software vendor rather than a formal standard. |
Terminals / pins
| Pin | Name |
|---|---|
| vcc | VCC |
| clk | CLK |
| dat | DAT |
Typical values
Supply voltage: 2.6–5.5 V (HX711). Full-scale output of load cell: typically 1–3 mV/V excitation. ADC resolution: 24 bits. Output data rate: 10 Hz or 80 Hz. Gain settings: 32 (channel B), 64 or 128 (channel A).
Where the Load Cell (HX711) symbol is used
- Postal and kitchen digital scales with Arduino or similar microcontrollers
- Industrial conveyor belt weighing systems requiring continuous mass measurement
- Smart bins and waste-management systems that measure fill level by weight
- Structural health monitoring rigs measuring beam deflection under load
- Medical devices such as infant weighing scales and hospital bed scales
- Agricultural yield monitoring attached to grain hoppers or silos
Example
In a typical Arduino kitchen-scale circuit, the load cell symbol connects its VCC pin to the Arduino 5 V rail and GND to common ground; the DAT pin links to Arduino digital pin 3 and CLK to digital pin 2. The Arduino runs the HX711 library, reads 24-bit values, applies a calibration factor, and displays the result in grams on an LCD module.
Key facts
- The Load Cell (HX711) symbol represents a strain-gauge force sensor paired with the HX711 24-bit ADC, forming a complete weight-measurement subsystem.
- The HX711 communicates with a microcontroller via two pins: CLK (clock driven by the MCU) and DAT (data output from the HX711), with no standard I2C or SPI bus required.
- The HX711 provides a programmable gain amplifier with gain settings of 32 (channel B), 64 (channel A), or 128 (channel A) to accommodate load cells with different sensitivity ratings.
- Load cells use a Wheatstone bridge of four strain gauges; the HX711 measures the differential voltage across the bridge, rejecting common-mode noise.
- The ADC delivers 24-bit resolution at 10 Hz (default) or 80 Hz, giving sub-milligram resolution on small-capacity load cells.
- Supply voltage for the HX711 is 2.6–5.5 V, making it compatible with both 3.3 V and 5 V microcontroller systems.
- OIML R 60 defines accuracy classes (C1–C6) for load cells used in legal-for-trade weighing instruments.
Frequently asked questions
What does the Load Cell HX711 symbol mean in a circuit diagram?
The Load Cell (HX711) symbol represents a weight-sensing subsystem consisting of a strain-gauge load cell (the mechanical transducer) and an HX711 24-bit ADC (the signal-conditioning and digitising IC). The symbol indicates that a microcontroller can read weight or force measurements via two digital pins: CLK and DAT.
What do the pins VCC, CLK, and DAT mean on the HX711 symbol?
VCC is the positive supply voltage (2.6–5.5 V); CLK is the serial clock signal driven by the microcontroller to shift data out of the HX711; DAT (also labelled DOUT) is the serial data output line that carries the 24-bit measurement result back to the microcontroller. No additional chip-select or I2C address pin is required.
What is the difference between a load cell and an HX711?
A load cell is the passive mechanical sensor — a metal beam fitted with strain gauges that produces a small differential voltage proportional to applied force. The HX711 is the active IC that amplifies that signal (gain 32–128) and converts it to a 24-bit digital value. The HX711 symbol in a schematic represents both components together as a functional block.
What standard defines the load cell symbol used in schematics?
No dedicated IEC 60617 or ANSI Y32.2/IEEE 315 glyph exists for the HX711 load-cell module. It is represented as a general functional block per IEEE 315-1975 block-diagram conventions, with its function identified by a text label inside or beside the block.
What is the HX711 gain and why does it matter?
The HX711 has a programmable gain amplifier: gain 128 or 64 on channel A, and gain 32 on channel B. Higher gain is used with low-sensitivity load cells (small mV/V output) to maximise ADC dynamic range. The gain is selected by the number of CLK pulses sent after each conversion (25 = gain 128 channel A, 26 = gain 64 channel A, 27 = gain 32 channel B).
What typical applications use the Load Cell HX711 symbol?
Common applications include Arduino-based kitchen and postal scales, smart bins, structural load testing, industrial conveyor weighing, agricultural grain-hopper monitoring, and medical weighing equipment. The symbol appears in maker/hobbyist schematics wherever automated weight measurement is required.
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