What is the calibration and adjustment of load cells?

Single-point calibration

Single-point calibration is the easiest calibration method. It’s best for cases where you only need accurate measurements at one load or torque. If the force sensor is linear and repeatable, you can use a single-point calibration. This fixes zero offset errors or zero balance, as long as the slope is right for the measurement range.
Calibrating a single-point force sensor also checks for “output drift.” This helps fix any decline in sensor performance as time goes by.

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Two-point calibration

Two-point calibration is more complex and more precise than single-point calibration. In two-point calibration, we adjust the sensor offset at two output values. This makes a straight line. It helps measure force with greater precision on the scale. It is generally recommended to use the two points as zero and full scale (rated output).
Load cells and torque sensors exhibit a linear response throughout their measuring range. Because of this, a two-point calibration is often recommended. This method fixes slope errors linked to load cell sensitivity. It also corrects offset errors related to zero balance.
With the new zero offset and slope (sensor sensitivity), we can create a linear equation. It describes the sensor output as follows: Vout = sensitivity * load + zero_offset.

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Five-point calibration (multi-point curve fitting)

Some key uses require the force sensor to be very accurate within a specific measurement range. In these cases, you need a five-point load cell calibration. This defines the calibration curve. It also ensures accurate measurements in the specified range.
Technicians usually do a five-point calibration. They check at 0%, 20%, 40%, 60%, 80%, and 100% of the measurement range.
- 0%: zero offset adjustment (or zero balance);
- 20%, 40%, 60%, 80%: linearity adjustment;
- 100%: span or slope adjustment (sensitivity).
In the five-point calibration of the force sensor, we take readings at both rising and falling values. This helps us test how consistent the force measurement system is. It includes both the sensor and the signal conditioner.

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Most force sensors connect to a reading display or signal conditioner. This setup creates a complete force measurement system. So, always connect the instrument to the sensor. Next, calibrate it with standard equipment in the torque sensor calibration lab as a system. For example, think about the 50-lb LSB205 miniature S-beam load cell. It works with the IAA200 4-20 mA current output amplifier and a 10-foot cable. When the customer asks, we will get five readings from the sensor. We will take these at loads of 0 lb (no load), 10 lb, 20 lb, 30 lb, 40 lb, and 50 lb. We will test the sensor on both upward and downward scales.