Load Cell Amplifier HX711 Breakout Hookup Guide

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Load Cell Setup

Depending on the type of load cell you are using, the configuration of how it should be hooked up to plates or surfaces will change. We'll list a few different types of setups below.

Four types of strain gauge load cells, two bar load cell and two disc load cells

A selection of different load cells

Bar-Type Load Cell

Usually with larger, non-push button bar load cells you will want to hook up the load cell between two plates in a "Z" shape.

Two bar strain gauge load cells

Bar strain gauge based load cells

As shown below, the bar-type load cell is mounted with fitting screws and spacers so that the strain can be correctly measured. Note that only one side of the load cell is screwed into each board when a bar-type load cell is placed between two plates. This provides a moment of force, or torque, on the strain gauge rather than just compression force, which is easier to measure and much more accurate.

Bar strain gauge load cell set up in a "Z" formation between two plates

Bar load cell between a two plate configuration

S-Type Load Cell

S-type load cells can measure compression, tension, or both due to its design.

S Type Load cell

Besides placing the load cell between plates, the s-type can be used to measure suspended tanks or hoppers. You can think of this as a load attached to a crane. Below is an s-type load cell with two threaded, rod end bearings.

S type load cell hooked up to two loops

S-type load cell configuration

Single, Strain Gauge Load Cells (i.e. Load Sensors)

For single, strain gauge load cells, they can be placed at equal distances with respect to each other underneath a platform.

load cell

The image below shows four, single strain gauge (i.e. the load sensor) arranged in a wheatstone bridge configuration. This configuration is also possible with four button-type load cells.

SparkFun's strain gauge load cell combinator board hooked up to a home scale, possible configuration for four disc load cells

SparkFun's strain gauge load cell combinator board hooked up to a home scale, possible four disc load cell configuration in something like a bathroom scale

Button/Disk-Type Load Cells

For smaller, push-button or disc load cells, you will want to make sure to screw in the disc to a bottom plate (or surface you are measuring force against), and center the beam, plate, or whatever else you are wishing to measure the force of onto the "button" on the top.

Two disc strain gauge load cells

Usually another plate with a hole is used to make sure whatever you are measuring is hitting the same spot on the load cell each time, but it is not necessary. Below are images of four button-type load cells placed at equal distances with respect to each other under a platform. Make sure to read the datasheet for the load cell you are using and get the correct screws to fit into it.

push-button load cells in a custom built scale enclosure push-button load cells under a custom built scale enclosure
Push Button Load Cells from the IoT Industrial Scale tutorial Push Button Load Cells Inside a Custom Built Scale

Variances in Measurements

Load cell measurements can be off by +/- 5% due to a range of things including temperature, creep, vibration, drift, and other electrical and mechanical interferences. Before you install your scale, take a moment and design your system to allow for easy calibration or be able to adjust the code parameters to account for these variations.